Figure Descriptions
Figure 1.1
This illustration shows the biological organization of the human body as a pyramid with six main levels. The chemical level is at the apex of the pyramid, where atoms bond to form molecules with three-dimensional structures. The molecular sublevel is presented as an example with two white hydrogen atoms bonding to a red oxygen atom to create water. The next level down on the pyramid is the cellular level, as illustrated with a long, tapered, smooth muscle cell; at this level, a variety of molecules combine to form the interior fluid and organelles of a body cell. The next level down is the tissue level, a community of similar cells that forms body tissue; the example given here is a section of smooth muscle tissue, which contains many smooth muscle cells closely bound side by side. The next level down is the organ level, as illustrated with the urinary bladder and urethra. The urinary bladder contains smooth muscle, while the urethra contains skeletal muscle; these are both examples of muscle tissues. The next level down is the organ system level, as illustrated by the entire urinary system, containing the kidneys, ureters, bladder, and urethra; at this level, two or more organs work closely together to perform the functions of a body system. At the base of the pyramid is the organismal level, as illustrated with a woman drinking water; at this level, many organ systems work harmoniously together to perform the functions of an independent organism.
Figure 1.2
This illustration shows six silhouettes of a human body, male and female, each showing the components of a different organ system. The integumentary system encloses internal body structures and is the site of many sensory receptors; it includes the hair, skin, and nails. The skeletal system supports the body and, along with the muscular system, enables movement; it includes cartilage, such as that at the tip of the nose, as well as the bones and joints. The muscular system enables movement, along with the skeletal system, but also helps maintain body temperature; it includes skeletal muscles as well as tendons that connect skeletal muscles to bones. The nervous system detects and processes sensory information and activates bodily responses; it includes the brain, spinal cord, and peripheral nerves, such as those located in the limbs. The endocrine system secretes hormones and regulates physiological processes; it includes the pituitary gland in the brain, the thyroid gland in the throat, the pancreas in the abdomen, the adrenal glands on top of the kidneys, and the testes in the scrotum of males as well as the ovaries in the pelvic region of females. The cardiovascular system delivers oxygen and nutrients to the tissues, equalizes temperature in the body, and performs many other functions; it includes the heart and blood vessels.
Figure 1.3
This illustration shows six silhouettes of a human body, male and female, each showing the components of a different organ system. The lymphatic system returns fluid to the blood and defends against pathogens; it includes the thymus in the chest, the spleen in the abdomen, the lymphatic vessels that spread throughout the body, and the lymph nodes distributed along the lymphatic vessels. The respiratory system removes carbon dioxide from the body and delivers oxygen to the blood; it includes the nasal passages, the trachea, and the lungs. The digestive system processes food for use by the body and removes wastes from undigested food; it includes the stomach, the liver, the gall bladder (connected to the liver), the large intestine, and the small intestine. The urinary system controls water balance in the body and removes and excretes waste from the blood; it includes the kidneys and the urinary bladder. The reproductive systems of males and females produce sex hormones and gametes; the male reproductive system is specialized to deliver gametes to the female, while the female reproductive system is specialized to support the embryo and fetus until birth and produce milk for the infant after birth. The male reproductive system includes the two testes within the scrotum as well as the epididymis, which wraps around each testis; the female reproductive system includes the mammary glands within the breasts and the ovaries and uterus within the pelvic cavity.
Figure 1.5
This figure shows two flowcharts labelled A and B. Chart A shows a general negative feedback loop. The loop starts with a stimulus perceived by a sensor, which sends that information to a control centre. The control centre sends a processed response as a signal to an effector, which creates a response to correct the condition; once this is corrected, it feeds back to the stimulus to inhibit the sensor from receiving more signal from the stimulus, which was already corrected by this process. Chart B shows body temperature regulation as an example of a negative feedback system. Here, the stimulus is body temperature exceeding 37°C. The sensor is a set of nerve cells in the skin and brain, and the control centre is the temperature regulatory centre in the brain; the effectors are sweat glands throughout the body that increase their secretion, which leads to heat loss to inhibit the rising body temperature, which then feeds back to the signal to inhibit the nerve cells in the skin and brain from responding, as the stimulus was eliminated.
Figure 1.6
This diagram shows the steps of a positive feedback loop as a series of stepwise arrows looping around a diagram of an infant within the uterus of a pregnant woman. The stimulus is the physical pressure by the head of the fetus against the cervix, transmitting nerve impulses from the cervix to the brain. Next, the brain stimulates the pituitary gland to secrete oxytocin, which is carried in the bloodstream to the uterus. Finally, the oxytocin stimulates uterine contractions and pushes the fetus harder into the cervix, combined with the relaxation of the cervix. As the head of the fetus pushes against the cervix with increasing force, the uterine contractions grow stronger and more frequent. This mechanism is a positive feedback loop.
Figure 1.7
This diagram shows anterior and posterior views of the human body with all regional labels. In the anterior view, labels identify the frons or forehead (frontal), cranium or skull (cranial), facies or face (facial), oris or mouth (oral), mentis or chin (mental), oculus or eye (orbital or ocular), bucca or cheek (buccal), auris or ear (otic), nasus or nose (nasal), cervicis or neck (cervical), thorcis or thorax or chest (thoracic), mamma or breast (mammary), abdomen (abdominal), umbilicus or navel (umbilical), hip (coxal), pelvis (pelvic), inguen or groin (inguinal), pubis (pubic), axilla or armpit (axillary), brachium or arm (brachial), antecubitis or front of elbow (antecubital), antebrachium or forearm (antebrachial), carpus or wrist (carpal), pollex or thumb, palma or palm (palmar), digits (phalanges) or fingers (digital or phalangeal), patella or kneecap (patellar), crus or leg (crural), tarsus or ankle (tarsal), digits (phalanges) or toes (digital or phalangeal), femur or thigh (femoral), pes or foot (pedal), and hallux or great toe. The posterior view labels the cephalon or head (cephalic), cervicis or neck (cervical), shoulder (acromial), dorsum or back (dorsal), brachium or arm (brachial), olecranon or back of elbow (olecranal), lumbus or loin (lumbar), sacrum (sacral), antebrachium or forearm (antebrachial), manus or hand (manual), gluteus or buttock (gluteal), femur or thigh (femoral), popliteus or back of knee (popliteal), sura or calf (sural), calcaneus or heel of foot (calcaneal), and planta or sole of foot (plantar). Both diagrams mark the upper limb and lower limb.
Figure 1.8
This illustration shows two diagrams: one of a side view of a female and the other of an anterior view of a female. Each diagram shows directional terms using double-sided arrows. On the left diagram, which is the lateral view, the cranial-caudal arrow runs vertically behind the torso and lower abdomen; the cranial arrow is pointing toward the back of the head, while the caudal arrow is pointing toward the tailbone. The posterior-anterior arrow is running horizontally through the back and chest; the posterior or dorsal arrow is pointing toward the back, while the anterior or ventral arrow is pointing toward the chest. On the right diagram, which is the anterior view, the proximal-distal arrow is on the left arm (“left” refers to the left side of the woman’s body from her perspective, while “right” refers to the right side of the woman’s body from her perspective); the proximal arrow is pointing up toward the left shoulder, while the distal arrow is pointing down toward the left hand. The same example is given for the right leg; the proximal arrow is pointing up toward the right hip, while the distal arrow is pointing down toward the right foot. The lateral-medial arrow is running horizontally on the abdomen; the medial arrow is pointing toward the navel (umbilicus), while the lateral arrow is pointing away from the body to the right. The illustration also describes the terms “superior,” which refers to the orientation toward the head, and “inferior,” which describes the orientation toward the feet.
Figure 1.10
This illustration shows lateral (right) and anterior (front) views of the body and highlights the body cavities with different colours. The cranial cavity is a large, bean-shaped cavity filling most of the upper skull, where the brain is located. The vertebral cavity is a very narrow, threadlike cavity running from the cranial cavity down the entire length of the spinal cord. Together, the cranial cavity and vertebral cavity can be referred to as the dorsal body cavity. The thoracic cavity consists of three cavities (detailed on the anterior view) that fill the interior area of the chest. The two pleural cavities are situated on both sides of the body, anterior to the spine and lateral to the breastbone. The superior mediastinum is a wedge-shaped cavity located between the superior regions of the two thoracic cavities. The pericardial cavity within the mediastinum is located at the centre of the chest below the superior mediastinum—it roughly outlines the shape of the heart. The diaphragm divides the thoracic and the abdominal cavities. The abdominal cavity occupies the entire lower half of the trunk, anterior to the spine. Just under the abdominal cavity, anterior to the buttocks, is the pelvic cavity. The pelvic cavity is funnel-shaped and is located inferior and anterior to the abdominal cavity. There is no anatomical structure between these two body cavities, so together, the abdominal and pelvic cavities can be referred to as the abdominopelvic cavity. The thoracic, abdominal, and pelvic cavities together can be referred to as the ventral body cavity.
Figure 1.11
This illustration has two parts. Part A (left) shows the nine abdominopelvic regions named based on their anatomical positions. For example, the right hypochondriac region is located on the left in the illustration, but anatomically, it is on the right side of the body. It contains the base of the right ribs, part of the liver, and part of the gall bladder. The upper right square is the left hypochondriac region and contains the base of the left ribs, part of the liver, and part of the stomach. The epigastric region is the upper central square and contains the bottom edge of the liver, the gall bladder, and the upper areas of the stomach. The diaphragm curves like an upside-down U over these three regions. The central left square is called the right lumbar region and contains the right part of the colon and the right part of the small intestines. The central middle square is the umbilical region and contains part of the stomach, part of the liver, the central part of the colon, and the central part of the small intestines. The central right square is called the left lumbar region and contains the left part of the colon, cecum, and small intestines. The lower left square is the right iliac region and contains the right pelvic bone and part of the colon. The lower central square is the hypogastric region and contains the bottom of the pubic bones, the upper regions of the bladder, and the lower region of the small intestine. The lower right square is the left iliac region and contains the left pelvic bone and the lower left regions of the small intestine. Part B shows four abdominopelvic quadrants. The upper left square is the right upper quadrant (RUQ) and includes the lower right ribs, the right side of the liver, the gall bladder, part of the stomach, and part of the colon. The upper right square is the left upper quadrant (LUQ) and includes the lower left ribs, part of the stomach, part of the liver, and part of the colon. The lower left square is the right lower quadrant (RLQ) and includes the right half of the small intestines, part of the colon, the right pelvic bone, and the upper right area of the bladder. The lower right square is the left lower quadrant (LLQ) and contains the left half of the small intestine, the left pelvic bone, and the upper left area of the bladder.
Figure 1.12
This diagram shows the pericardium on the left next to an analogy of a hand punching a balloon on the right. The pericardium is a two-layered sac that surrounds the entire heart except where the blood vessels emerge on the heart’s superior side. The pericardium has two layers because it folds over itself in the shape of the letter U. The inner layer that borders the heart is the visceral pericardium (in contact with the hand on the analogy), while the outer layer is the parietal pericardium (the outer balloon layer on the analogy). The space between the two layers is called the pericardial cavity (the air space on the analogy) and is filled with fluid. The heart sits in the cavity much like a fist punching into a balloon. The balloon surrounds the lower part of the fist with a two-layered sac, with the top of the balloon, where it contacts the fist, being analogous to the visceral pericardium. The bottom of the balloon, where it is tied off, is analogous to the parietal pericardium. The air within the balloon is analogous to the pericardial cavity, which in reality is filled with fluid.
Figure 2.6
The top panel in this figure shows two hydrogen atoms sharing two electrons, which is a single covalent bond. The hydrogen atoms each share their solitary electron. The middle panel in this figure shows a molecule of oxygen gas with two oxygen atoms sharing four electrons, which is a double covalent bond. An atom of oxygen has six electrons in its valence shell and achieves stability by sharing two pairs of electrons. The bottom panel in this figure shows two oxygen atoms and one carbon atom sharing two pairs of electrons, which is two double covalent bonds. An atom of carbon and two atoms of oxygen achieve stability by sharing two electron pairs each.
Figure 2.7
This figure shows three different models for diagraming the structure of a water molecule. The top panel uses the planetary model and shows two hydrogen atoms and one oxygen atom with electrons in orbit. The unshared electrons in the outer shell of the oxygen atom are weakly negative, while the outer shells of the hydrogen atoms are weakly positive. The lower left panel shows a three-dimensional model of a water molecule, where spheres representing the three atoms are pressed up against each other. The lower right panel shows the structural formula for a water molecule, where the three spheres are separated and the bonds between them are indicated by a line.
Figure 3.8
This diagram shows four sodium-potassium pumps embedded in the plasma membrane. Potassium is pumped from the extracellular space, where it is highly concentrated, into the cytoplasm. Sodium is pumped out of the cytoplasm, where it is highly concentrated, into the extracellular space. An ATP molecule is shown bonding to the potassium pump from the cytoplasm side of the membrane. This molecule detaches from the potassium pump and becomes an ADP molecule, leaving a phosphate molecule behind. This phosphate molecule is released back into the cytoplasm, along with potassium ions transported through the membrane via the pump.
Figure 3.9
This image shows the three different types of endocytosis. The left panel shows phagocytosis, where a large particle is seen to be engulfed by the membrane and released into the intracellular fluid as a vacuole. In the middle panel, pinocytosis is shown, where a small particle is engulfed by the membrane and released into the intracellular fluid as a vesicle. In the right panel, receptor-mediated endocytosis is shown, where the ligand binds to a receptor on the exterior of the cell membrane. It is then engulfed by the membrane and released into the intracellular fluid as a coated vesicle.
Figure 3.13
This figure shows the structure of the Golgi apparatus. The diagram in the left panel shows the location and structure of the Golgi apparatus between the plasma membrane and the rough endoplasmic reticulum and nucleus. Transport vesicles bring material from the rough endoplasmic reticulum to the cisternae of the Golgi apparatus. Secretory vesicles bring material from the Golgi apparatus to the plasma membrane, where it is transmitted into the extracellular fluid. The right panel presents a micrograph showing the folds of the Golgi in detail. The trans and cis faces of the organelle are labelled.
Figure 3.15
This figure shows the different cytoskeletal components in a cell. The left panel shows the microtubules with the structure of the column formed by tubulin dimers. The tubulin dimer looks like two strings of pearls coiled into a tubular column approximately 25 nanometres in diameter. The middle panel shows the actin filaments and the helical structure formed by the filaments. The filaments are composed of individual actin subunits, and the helical structure is approximately 7 nanometres across. The right panel shows the fibrous structure of the intermediate filaments with different keratins coiled together. It has a rope-like coiled structure that is approximately 8 to 12 nanometres across.
Figure 3.20
This figure shows the DNA double helix in the top left panel. The different nucleotides are colour-coded and combine with the sugar-phosphate backbone to form a twisted ladderlike structure. In the top right panel, the interaction between the nucleotide molecules through hydrogen bonds and the location of the sugar-phosphate backbone is shown. Thymine and adenine molecules form two hydrogen bonds between them, while guanine and cytosine form three. Opposite their hydrogen bonds, each nitrogenous base is bonded to a sugar molecule, which in turn is bonded to a phosphate molecule. These latter two molecules compose the sugar-phosphate backbone of DNA. In the bottom panel, the molecular structure of a nucleotide is described in detail, showing where the nitrogenous base joins the sugar molecule and where the sugar joins the phosphate.
Figure 3.26
This tabular image shows the different stages of mitosis and cytokinesis using both drawings and text. The top panel is a series of schematics for each step, followed by text listing the important aspects of that step. The bottom panel shows fluorescent micrographs for the corresponding stage. The first five stages illustrate mitosis, and the last stage illustrates cytokinesis. In prophase, chromosomes condense and become visible, spindle fibres emerge from the centrosomes, the nuclear envelope breaks down, and centrosomes move toward opposite poles of the cell. In prometaphase, chromosomes continue to condense, kinetochores appear at the centromeres, and mitotic spindle microtubules attach to kinetochores. In metaphase, chromosomes are lined up at the metaphase plate, and each sister chromatid is attached to a spindle fibre originating from opposite poles. In anaphase, centromeres split in two, sister chromatids (now called chromosomes) are pulled toward opposite poles, and certain spindle fibres begin to elongate the cell. Mitosis concludes with telophase, wherein chromosomes arrive at opposite poles and begin to decondense, the nuclear envelope material surrounds each set of chromosomes, the mitotic spindle breaks down, and spindle fibres continue to push poles apart. Finally, in cytokinesis for animal cells, a cleavage furrow separates the daughter cells, while for plant cells, a cell plate, the precursor to a new cell wall, separates the daughter cells.
Figure 4.1
This diagram shows the silhouette of a female surrounded by four micrographs of tissue. Each micrograph has arrows pointing to the organs where that tissue is found. The upper left micrograph shows nervous tissue that is whitish with several large, purple, irregularly shaped neurons embedded throughout. Nervous tissue is found in the brain, spinal cord, and nerves. The upper right micrograph shows muscle tissue that is red with elongated cells and prominent, purple nuclei. Cardiac muscle is found in the heart. Smooth muscle is found in internal organs, such as the stomach. Skeletal muscle is found in parts that are moved voluntarily, such as the arms. The lower left micrograph shows epithelial tissue. This tissue is purple with many round, purple cells with dark-purple nuclei. Epithelial tissue is found in the lining of GI tract organs and other hollow organs, such as the small intestine. Epithelial tissue also composes the outer layer of the skin, known as the epidermis. Finally, the lower right micrograph shows connective tissue, which is composed of very loosely packed purple cells and fibres. There are large open spaces between clumps of cells and fibres. Connective tissue is found in the leg within fat and other soft padding tissue as well as bones and tendons.
Figure 4.2
This illustration shows the silhouette of a female from an anterior view. Several organs are showing in her neck, thorax, abdomen, left arm, and right leg. Text boxes point out and describe the mucous membranes in several different organs. The topmost box points to the mouth and trachea. It states that mucous membranes line the digestive, respiratory, urinary, and reproductive tracts. They are coated with the secretions of mucous glands. The second box points to the outside edge of the lungs as well as the large intestine. It states that serous membranes line body cavities that are closed to the exterior of the body, including the peritoneal, pleural, and pericardial cavities. The third box points to the skin of the hand. It states that the cutaneous membrane, also known as the skin, covers the body surface. The fourth box points to the right knee. It states that synovial membranes line joint cavities and produce the fluid within the joint.
Figure 4.3
These three illustrations each show the edges of two vertical cell membranes. The cell membranes are viewed partially from the side so that the inside edge of the right cell membrane is visible. The upper left image shows a tight junction. The two cell membranes are bound by transmembrane protein strands. The proteins travel the inside edge of the right cell membrane and cross over to the left cell membrane, cinching the two membranes together. The cell membranes are still somewhat separated in between neighbouring strands, creating intercellular spaces. The upper right diagram shows a gap junction. Gap junctions are composed of two interlocking connexins, which are round, hollow tubes that extend through the cell membranes. Two connexins, one from the left cell membrane and the other from the right cell membrane, meet between the two cells, forming a connexon. Even at the site of the connexon, there is a small gap between the cell membranes. On the inside edge of the right cell membrane, the gap junction appears as a depression. Three connexins are embedded in the membranes like buttons on a shirt. The bottom images show the three types of anchoring junctions. The left image shows a desmosome. Here, the inside edges of both the right and left cell membranes have brown, round plaques. Each plaque has tentacle-like intermediate filaments (keratin) that extend into each cell’s cytoplasm. The two plaques are connected across the intercellular space by several interlocking transmembrane glycoproteins (cadherin). The connected glycoproteins look similar to a zipped-up zipper between the right and left cell membranes. The right image shows an example of adherens. These are similar to desmosomes, with two plaques on the inside edge of each cell membrane connected across the intercellular space by glycoproteins. However, the plaques do not contain the tentacle-like intermediate filaments branching into the cytoplasm. Instead, the plaques are ribbed with green actin filaments. The filaments are neatly arranged in parallel, horizontal strands on the surface of the plaque facing the cytoplasm. The bottom image shows a hemidesmosome. Rather than being located between two neighbouring cells, the hemidesmosome is located between the bottom of a cell and the basement membrane. A hemidesmosome contains a single plaque on the inside edge of the cell membrane. Like the desmosome, intermediate filaments project from the plaque into the cytoplasm. The opposite side of the plaque has purple, knob-shaped integrins extending out to the basal lamina of the basement membrane.
Figure 4.4
This figure is a table showing the appearance of squamous, cuboidal, and columnar epithelial tissues. Simple and stratified forms are shown for each tissue type. In a simple squamous epithelium, the cells are flattened and single layered. In a simple cuboidal epithelium, the cells are cube-shaped and single layered. In a simple columnar epithelium, the cells are rectangular and attached to the basement membrane on one of their narrow sides so that each cell is standing up like a column. There is only one layer of cells. In a pseudostratified columnar epithelium, the cells are column-like in appearance, but they vary in height. The taller cells bend over the tops of the shorter cells so that the top of the epithelial tissue is continuous. There is only one layer of cells. A stratified squamous epithelium contains many layers of flattened cells. A stratified cuboidal epithelium contains many layers of cube-shaped cells. A stratified columnar epithelium contains many layers of rectangular, column-shaped cells.
Figure 4.5
This illustration shows a diagram of a goblet cell. The goblet cell is shaped roughly like an upside-down vase. The enlarged end at the top contains seven finger-like projections labelled microvilli. Below the microvilli, secretory vesicles containing mucin are moving from the upper half of the cell toward the microvilli. Below the secretory vesicles are several rough endoplasmic reticula and an irregularly shaped Golgi apparatus with secretory vesicles budding off of it. The narrow, lower half of the cell contains the oval-shaped nucleus as well as a few mitochondria and segments of the endoplasmic reticulum.
Figure 4.6
This figure is a table with three columns and nine rows. The leftmost column is titled “Cells” and contains a drawing in each row showing how epithelial cells are arranged above a basement membrane. The middle column is titled “Location,” while the rightmost column is titled “Function.” In a simple squamous epithelium, the cells are flattened and single layered. Simple squamous cells are found in the air sacs of the lungs and in the lining of the heart, blood vessels, and lymphatic vessels. Their function is to allow materials to pass through by diffusion and filtration as well as to secrete lubricating substances. In a simple cuboidal epithelium, the cells are cube-shaped, single layered, and located in ducts and secretory portions of small glands as well as in the kidney tubules. The function of a simple cuboidal epithelium is to secrete and absorb. In a simple columnar epithelium, the cells are rectangular and attached to the basement membrane on one of their narrow sides so that each cell is standing up like a column. There is only one layer of cells. A simple columnar epithelium is found in ciliated tissues, including the larger bronchioles, uterine tubes, and uterus, as well as in smooth, nonciliated tissues, such as the digestive tract and bladder. The function of a simple columnar epithelium is to absorb substances but also to secrete mucus and enzymes. In a pseudostratified columnar epithelium, the cells are column-like in appearance, but they vary in height. The taller cells bend over the tops of the shorter cells so that the top of the epithelial tissue is continuous. There is only one layer of cells. A pseudostratified columnar epithelium lines the bronchi, the trachea, and much of the upper respiratory tract. The function of a pseudostratified columnar epithelium is to secrete mucus and also move that mucus using the hairlike cilia projecting from the top of each cell. A stratified squamous epithelium contains many layers of flattened cells. A stratified squamous epithelium lines the esophagus, mouth, and vagina. The function of a stratified squamous epithelium is to protect against abrasion. A stratified cuboidal epithelium contains many layers of cube-shaped cells. A stratified cuboidal epithelium is found in the sweat glands, salivary glands, and mammary glands. The function of a stratified cuboidal epithelium is to protect other tissues of the body. A stratified columnar epithelium contains many layers of rectangular, column-shaped cells. A stratified columnar epithelium is located in the male and female urethrae and the ducts of some glands. The function of a stratified columnar epithelium is to secrete and protect. A transitional epithelium consists of many layers of irregularly shaped cells of diverse sizes. A transitional epithelium is found lining the urinary bladder, urethra, and ureters. The function of a transitional epithelium is to allow the urinary organs to expand and stretch.
Figure 4.7
These three diagrams show the three modes of secretion. All three diagrams show three orange cells in a line attached to a basement membrane. Each cell has a large nucleus in its lower half. The upper half of each cell contains a Golgi apparatus, which appears like an upside-down jellyfish. Yellow secretory vesicles are budding from the top end of the Golgi apparatus. Each vesicle contains several orange circles, which are the secreted substance. In merocrine secretion, the secretory vesicles travel to the top edge of the cell and release the secretion from the cell by melding with the cell membrane. In apocrine secretion, the top third of the cell, which contains the secretory vesicles, pinches in at the sides and then completely disconnects above the Golgi complex. The pinched-off portion of the cell is the secretion, as it contains the majority of the secretory vesicles. In holocrine secretion, the upper third of the cell, just above the Golgi complex, forms many finger-like projections. Each projection contains several vesicles. The tips of the projections that contain secretory vesicles bud off from the cell. In this method of secretion, the mature cell eventually dies and becomes the secretory product.
Figure 4.9
The left image shows a diagram of connective tissue. As a whole, the connective tissue appears somewhat disorganized, with fibres and cells mixed together heterogeneously. There are many open spaces between the embedded elements, suggesting that the connective tissue is somewhat loosely packed. The thickest fibres are collagen fibres; the thinner fibres are elastic fibres. Both the collagen fibres and the elastic fibres crisscross randomly throughout the tissue. In addition, a net of reticular fibres appears in the upper part of the diagram. Two yellow and oval-shaped adipocytes are embedded below the reticular fibre net, with a small dark nucleus squeezed into one corner of the cell. A mesenchymal cell is next to one of the adipocytes. The cell is rectangular and has four projections stemming from each corner of the cell. The projections appear to attach to the nearby collagen fibres. A fibroblast is located at the centre of the diagram. The fibroblast appears similar to the mesenchymal cell, except that it is larger and has more projections. Finally, a macrophage is in the lower right of the diagram. The macrophage is a white, oval-shaped disc with a prominent nucleus. The right diagram is a micrograph of connective tissue. The tissue is mostly stained pink; however, the thick collagen fibres crisscrossing the tissue are white. Five adipocytes also appear white, except for their cell membrane and nucleus, which stained dark. A mesenchymal cell occupies the space between two adipocytes. It stains a very deep purple, but its shape is unclear in the micrograph. A fibrocyte is also visible as an oval-shaped cell with a deep-purple nucleus.
Figure 4.12
Part A shows a diagram of regular dense connective tissue alongside a micrograph. The tissue is composed of parallel, threadlike collagen fibres running vertically through the diagram. Between the vertical fibres, several dark, oval-shaped fibroblast nuclei are visible. In the micrograph, the whitish collagen strands run horizontally. Several dark-purple fibroblast nuclei are embedded in the lightly stained matrix. Part B shows a diagram of irregular dense connective tissue on the left and a micrograph on the right. In the diagram, the collagen fibres are arranged in bundles that curve and loop throughout the tissue. The fibres within a bundle run parallel to each other, but separate bundles crisscross throughout the tissue. Because of this, the irregular dense connective tissue appears less organized than the regular dense connective tissue. This is also evident in the micrograph, where the white collagen bundles radiate throughout the micrograph in all directions. The fibroblasts are visible as red-stained cells with dark-purple nuclei.
Figure 4.13
The first row of this diagram is a drawing and a micrograph of hyaline cartilage. The cartilage contains chondrocytes encapsulated in lacunae. Several of the lacunae are joined into groups or small stacks and embedded in the surrounding matrix. The micrograph shows the lacunae as white rings surrounding the purple-stained chondrocytes. Some occur as joined pairs, while others are embedded singly within the pink-stained matrix. The middle row shows a diagram and a micrograph of fibrocartilage that contains many fine collagen fibres embedded in the matrix. The collagen fibres are roughly parallel to each other but run through the matrix in a wavy fashion. There are also four round chondrocyte cells embedded within the matrix. In the micrograph, the matrix is shaded red and the collagen fibres are visible in white. The lacunae are clearly visible as a faint purple ring containing several dark-purple chondrocytes. The bottom row shows a diagram and micrograph of elastic cartilage. In the diagram, fine elastic fibres are seen crisscrossing the matrix. Many of the elastic fibres branch off from each other, unlike the collagen fibres depicted in the previous two rows. The lacunae are clearly visible as white rings containing stained chondrocytes. The fibres stain deeply in this micrograph and can be seen crisscrossing through the tissue.
Figure 4.15
This figure shows three micrographs, each depicting one of the three muscle tissues. Picture A shows skeletal muscle tissue, which is dense strips of pink tissue. Many small nuclei are dispersed throughout the tissue. The nuclei are flat and elongated, with multiple nuclei clustered into each cell. Picture B shows smooth muscle, which is densely packed and looks similar to skeletal muscle except that each cell only has one oval-shaped nucleus. Picture C shows cardiac muscle. Unlike skeletal and smooth muscle cells, cardiac muscle cells are not densely packed. The cardiac cells are branched, creating a large amount of space between each muscle cell.
Figure 4.16
This figure shows a diagram of a neuron and a micrograph showing two neuron cells. The body of the neuron contains a single purple nucleus. The cell is irregularly shaped, having many projections emerging from its surface. Six sets of dendrites project from the top, right, and bottom edges of the cell. The dendrites are yellow and branch many times after leaving the cell, taking on the appearance of tiny trees. The axon projects from the left edge of the cell. The axon is a long cable-like structure that branches into several finger-like projections at its end. This is where the neuron makes contact with other cells. The area where the axon emerges from the cell body contains microfibrils and microtubules. The micrograph is considerably less magnified than the diagram. The neurons stain darkly, and their nuclei are clearly visible. Their irregular cell body is also visible, along with the beginning of the axons.
Figure 4.17
The left side of this diagram shows various types of nerve cells. The largest cell is a neuron. The central body of the neuron contains a single nucleus. Six sets of dendrites project from the top, left, and right edges of the neuron. The dendrites are yellow and branch many times after leaving the cell, taking on the appearance of tiny trees. The axon projects from the bottom edge of the cell and is covered with purple sheaths labelled as the myelin sheath. The sheath is not continuous but instead is a series of equally spaced segments along the axon. Another cell, called an oligodendrocyte, is spiderlike in appearance, with its leglike projections each connecting to a segment of the neuron’s myelin sheath. Above the neuron are three astrocytes. They are much smaller than the neuron, have no axons, and are also irregularly shaped cells with many dendrites projecting from the central body. Finally, a microglial cell is shown above the neuron. It is the smallest of the cells in this figure and is an elongated cell with many fine, tentacle-like projections. The projections are concentrated at the two ends of the cell, with the middle area lacking any projections. The right side of the micrograph of the neural tissue shows that this tissue is very heterogeneous, with both large and small cells embedded in the matrix. Much of the space between the cells is occupied by threadlike nerve fibres.
Figure 5.1
This illustration shows a cross-section of skin tissue. The outermost layer is called the epidermis and occupies one-fifth of the cross-section. Several hairs are emerging from the surface. The epidermis dives around one of the hairs, forming a follicle. The middle layer is called the dermis, which occupies four-fifths of the cross-section. The dermis contains an arrector pili muscle connected to one of the follicles. The dermis also contains an eccrine sweat gland, composed of a bunch of tubules. One tubule travels up from the bunch, through the epidermis, opening onto the surface of a pore. There are two string-like nerves travelling vertically through the dermis. The right nerve is attached to a Pacinian corpuscle, which is a yellow structure consisting of concentric ovals similar to an onion. The lowest level of the skin, the hypodermis, contains fatty tissue, arteries, and veins. Blood vessels travel from the hypodermis and connect to hair follicles and the arrector pili muscle in the dermis.
Figure 5.2
Part A is a micrograph showing a cross-section of thin skin. The topmost layer is a thin, translucent layer with irregular texture and areas where cells are sloughing off. The deepest layer is dark purple and extends into the third layer with finger-like projections. The third light purple layer contains thin bands of fibres and small, dark cells. The fourth and deepest layer is darker than the third layer but is still light purple. It contains thick fibre bands that are loosely packed. Part B is a magnified view of the epidermis of thick skin. It shows the topmost layer is five times thicker than the topmost layer of thin skin. The topmost layer of thick skin is also denser and less translucent than the topmost layer of thin skin.
Figure 5.4
This illustration shows a cross-section of the epidermis. The cells of the innermost layer, the stratum basale, are large and have a purple nucleus. The stratum basale curls around the dermis, which projects into the epidermis. The stratum basale transitions from the dermis and contains four layers of large, triangle-shaped keratinocytes. Fibres are visible within the spaces between keratinocytes in the stratum basale. A melanocyte is also present in this layer. The melanocyte possesses finger-like projections extending from its main cell body. The projections branch through the extracellular spaces between nearby keratinocytes. Above the stratum basale is the stratum spinosum, which consists of 8 to 10 layers of oval-shaped keratinocytes. The nucleus is present in these keratinocytes but has faded to a lighter purple. The stratum granulosum contains 3 to 5 layers of keratinocytes, each containing granules marked as red dots in its cytoplasm, labelled the lamellar granules. The stratum lucidum contains 4 layers of diamond-shaped cells with no nucleus, found only in the epithelium of thick skin. The stratum corneum contains 15 to 30 layers of keratinocytes with no nucleus or cytoplasm. A few of the cells in the topmost layer of the stratum corneum are flaking off from the skin.
Figure 5.5
This figure is an electron micrograph of skin tissue showing the layered structure of the epidermis above the dermis. The outermost layer is the stratum corneum, appearing as a dark, dense surface layer. Beneath it is the stratum granulosum, followed by the thicker stratum spinosum and the deepest epidermal layer, the stratum basale or germinativum, where new epidermal cells form. Below the epidermis lies the dermis, containing connective tissue and small blood vessels, including a labelled capillary. In the middle-right region of the image are remnants of a cross-sectioned shed hair and its follicle within the dermal tissue.
Figure 5.7
This figure consists of two diagrams side by side. The right diagram shows the development of light-coloured skin; the left shows the development of dark-coloured skin. In both, a brown melanocyte sits at the border between the dermis and epidermis. The melanocyte has a large nucleus and six finger-like extensions. These reach between cells of the stratum basalis. Sections of the extensions detach and travel through the skin. These are melanosomes. In the left diagram, both the melanocyte and melanosomes contain melanin particles, shown as dark dots. Melanosomes travel upward to outer skin layers, releasing melanin. As a result, keratinocytes in the left diagram contain several melanin particles that darken skin colour. In light-coloured skin, the melanocyte contains no melanin. It still releases melanosomes into upper layers of the skin; however, these melanosomes contain no melanin. Therefore, the skin does not darken and remains light.
Figure 5.8
This diagram shows a cross-section of the skin containing a hair follicle. The follicle is teardrop-shaped. Its enlarged base, labelled the hair bulb, is embedded in the hypodermis. The outermost layer of the follicle is the epidermis, which invaginates from the skin surface to envelope the follicle. Within the epidermis is the outer root sheath, which is only present on the hair bulb. It does not extend up the shaft of the hair. Within the outer root sheath is the inner root sheath. The inner root sheath extends about half of the way up the hair shaft, ending midway through the dermis. The hair matrix is the innermost layer. The hair matrix surrounds the bottom of the hair shaft, where it is embedded within the hair bulb. The hair shaft itself contains three layers: the outermost cuticle, a middle layer called the cortex, and an innermost layer called the medulla.
Figure 5.10
These two images show the anatomy of the fingernail region. The left image shows a dorsal view of a finger. The proximal nail fold is the part underneath where the skin of the finger connects with the edge of the nail. The eponychium is a thin, pink layer between the white proximal edge of the nail (the lunula) and the edge of the finger skin. The lunula appears as a crescent-shaped white area at the proximal edge of the pink-shaded nail. The lateral nail folds are where the sides of the nail contact the finger skin. The distal edge of the nail is white and is called the free edge. The nail grows distally out from the proximal nail fold. The right image shows a lateral view of the nail bed anatomy. In this view, one can see how the edge of the nail is located just proximal to the nail fold. This end of the nail, from which the nail grows, is called the nail root.
Figure 5.13
Part A is a photo of a man skiing with several snow-covered trees in the background. Part B is a diagram with a right and left half. The left half is titled “Heat is retained by your body,” while the right half is titled “Heat through radiation and convection.” Both show blood flowing from an artery through three capillary beds within the skin. The capillary beds are arranged vertically, with the topmost bed located along the boundary of the dermis and epidermis. The bottommost bed is located deep in the hypodermis. The middle bed is evenly spaced between the topmost and bottommost beds. In each capillary bed, oxygenated blood (red) enters the bed on the left and deoxygenated blood (blue) leaves the bed on the right. The left diagram shows a picture of snowflakes above the capillary beds, indicating that the weather is cold. Blood is only flowing through the deepest of the three capillary beds, as the upper beds are closed off to reduce heat loss from the outer layers of the skin. The right diagram shows a picture of the sun above the capillary beds, indicating that the weather is hot. Blood is flowing through all three capillary beds, allowing heat to radiate out of the blood, increasing heat loss, as demonstrated in part C with a photo of a man running through a forested trail on a summer day.
Figure 6.3
This illustration depicts an anterior view of the right femur, or thigh bone. The inferior end that connects to the knee is at the bottom of the diagram, and the superior end that connects to the hip is at the top of the diagram. The bottom end of the bone contains a smaller lateral bulge and a larger medial bulge. A blue articular cartilage covers the inner half of each bulge as well as the small trench that runs between the bulges. This area of the inferior end of the bone is labelled the distal epiphysis. Above the distal epiphysis is the metaphysis, where the bone tapers from the wide epiphysis into the relatively thin shaft. The entire length of the shaft is the diaphysis. The superior half of the femur is cut away to show its internal contents. The bone is covered with an outer translucent sheet called the periosteum. At the midpoint of the diaphysis, a nutrient artery travels through the periosteum and into the inner layers of the bone. The periosteum surrounds a white cylinder of solid bone labelled compact bone. The cavity at the centre of the compact bone is called the medullary cavity. The inner layer of the compact bone that lines the medullary cavity is called the endosteum. Within the diaphysis, the medullary cavity contains a cylinder of yellow bone marrow that is penetrated by the nutrient artery. The superior end of the femur is also connected to the diaphysis by a metaphysis. In this upper metaphysis, the bone gradually widens between the diaphysis and the proximal epiphysis. The proximal epiphysis of the femur is roughly hexagonal in shape. However, the upper right side of the hexagon has a large, protruding knob. The femur connects and rotates within the hip socket at this knob. The knob is covered with a blue-coloured articular cartilage. The internal anatomy of the upper metaphysis and proximal epiphysis is revealed. The medullary cavity in these regions is filled with the meshlike spongy bone. Red bone marrow occupies the many cavities within the spongy bone. There is a clear, white line separating the spongy bone of the upper metaphysis from that of the proximal epiphysis. This line is the epiphyseal line.
Figure 6.4
The top of this illustration shows an anterior view of the proximal end of the femur. The top image has two zoomed-in boxes. The left box is situated on the border between the diaphysis and the metaphysis. Its callout magnifies the periosteum on the right side of the femur. The view shows that the periosteum contains an outer fibrous layer composed of yellow fibres. The inner layer of the periosteum is called the cellular layer, which is composed of irregularly shaped cells. The cellular layer gradually shrinks in width as it transitions from the metaphysis to the diaphysis. A small blood vessel runs through both layers and enters the bone. The right zoomed-in box magnifies the endosteum on the left side of the bone. The box is situated just inferior to the border between the diaphysis and the metaphysic. It calls out the inner edge of the compact bone layer. The magnified view shows concentric circles of dark-coloured bone matrix. Between the circles are small cavities containing orange, diamond-shaped cells labelled osteocytes. The left edge of the bone matrix is lined with a single layer of flattened cells called the endosteum. There is a large cell, labelled an osteoclast, between two of the endosteum cells. The osteoclast is cutting a depression into the bony matrix under the endosteum. At another part of the endosteum, three smaller osteoblasts are secreting a blue substance that builds up the outermost layer of the bony matrix.
Figure 6.6
This illustration contains three diagrams. The left diagram is titled “Examples of processes formed where tendons or ligaments attach.” The image shows an anterior view of the femur and an anterior view of the humerus. For the femur, the distal epiphysis contains a smaller lateral bulge and a larger medial bulge. These are examples of condyles. The inner halves of the two condyles and the groove between them compose a facet. An oval-shaped ridge on the medial surface of the distal metaphysis is an example of a tubercle. On the proximal epiphysis of the femur, the large knob that attaches to the hip socket is an example of a head. The tip of the head contains a small depression that is an example of a fovea called the fovea capitis. On the humerus, the distal epiphysis contains a central depression that is an example of a fossa. Two condyles are located on the right and left sides of the fossa. The diaphysis of the humerus contains a small ridge running up the shaft that is an example of a tuberosity. The proximal epiphysis of the humerus contains a lateral and a medial bulge that are both examples of tubercles. Finally, a narrow groove runs from the centre of the proximal metaphysis to in between the medial and lateral condyles. This is an example of a sulcus. The right image is entitled “Examples of an elevation or depression.” It shows an anterior view of the hip bones. The hip bones are shaped like two wings that join at the bottom. The crest along the upper edge of each hip bone, at the tip of each “wing,” is an example of an elevation. A depression on the inner surface of both hip bones just under the crest is called a fossa. The lower right image is entitled “Examples of openings” and shows an anterior view of the skull. The bone underlying the chin is an example of a protuberance, while two small holes above each eye socket are examples of foramina. Five green sinuses surround the nose cavity. These are sinuses because they are hollowed-out cavities within the skull bones. A small channel leads into the corner of each eye, where the tear ducts occur. These two channels are both examples of a canal. Finally, the bones that form the posterior wall of the eye socket have a small crack running diagonally away from the nose. These are examples of fissures.
Figure 6.7
The top of this diagram shows the cross-section of a generic bone with three marked areas: the periosteum, the middle of the compact bone layer, and the inner edge of the compact bone where it transitions into the spongy bone. The periosteum points to two zoomed-in images. In one image, four osteoblast cells are sitting end to end on the periosteum. The osteoblasts are roughly square-shaped, except for one of the cells that is developing small, finger-like projections. Osteoblasts form the matrix of the bone. The other image called out from the periosteum shows a large, amorphous osteogenic cell sitting on the periosteum. The osteogenic cell is surrounded on both sides by a row of much smaller osteoblasts. The cell is shaped like a mushroom cap and also has finger-like projections. The cell is a stem cell that develops into other bone cells. The middle of the compact bone layer points to an osteocyte. The osteocyte is a thin cell and roughly diamond-shaped, with many branching, finger-like projections. Osteocytes maintain bone tissue. The inner edge of the compact bone points to an osteoclast. The osteoclast is a large, round cell with multiple nuclei. It also has rows of fine finger-like projections on its lower surface, where it is sitting on the compact bone. Osteoclasts reabsorb bone.
Figure 6.8
A generic long bone is shown at the top of this illustration. The bone is split in half lengthwise to show its internal anatomy. The outer gray covering of the bone is the periosteum. Within the periosteum is a thin layer of compact bone. The compact bone surrounds a central cavity called the medullary cavity. The medullary cavity is filled with spongy bone at the two epiphyses. A callout box shows that the main image is zooming in on the compact bone on the left side of the bone. In the main image, the periosteum is being peeled back to show its two layers. The outer layer of the periosteum is the outer fibrous layer. This layer has a periosteal artery and a periosteal vein running along its outside edge. The inner layer of the periosteum is the inner osteogenic layer. The compact bone lies to the right of the periosteum and occupies the majority of the main image. Two flat layers of compact bone line the inner surface of the osteogenic periosteum. These sheets of compact bone are called the circumferential lamellae. The majority of the compact bone has lamellae running perpendicular to that of the circumferential lamellae. These concentric lamellae are arranged in a series of concentric tubes. There are small cavities between the layers of concentric lamellae called lacunae. The centremost concentric lamella surrounds a hollow central canal. A blue vein, a red artery, a yellow nerve, and a green lymph vessel run vertically through the central canal. A set of concentric lamellae, its associated lacunae, and the vessels and nerves of the central canal are collectively called an osteon. The front edge of the diagram shows a longitudinal cross-section of one of the osteons. The vessels and nerves are visible running through the centre of the osteon throughout its length. In addition, blood vessels can run from the periosteum through the sides of the osteons and connect with the vessels of the central canal. The blood vessels travel through the sides of the osteons via a perforating canal. The open areas between neighbouring osteons are also filled with compact bone. This “filler” bone is referred to as the interstitial lamellae. At the far right of the compact bone, the edge of the spongy bone is visible. The spongy bone is a series of crisscrossing bony arches called trabeculae. There are many open spaces between the trabeculae, giving the spongy bone its spongelike appearance.
Figure 6.9
This illustration shows the spongy bone within the proximal epiphysis of the femur in two successively magnified images. The lower-magnification image shows two layers of crisscrossing trabeculae. The surface of each is dotted with small black holes, which are the openings of the canaliculi. One of the trabeculae is in a cross-section to show its internal layers. The outermost covering of the lamellae is called the endosteum. This endosteum surrounds several layers of concentric lamellae. The higher-magnification image shows the cross-section of the trabeculae more clearly. Three concentric lamellae are shown in this view, each possessing perpendicular black lines. These lines are the canaliculi and are oriented on the round lamellae, similar to the spokes of a wheel. In between the lamellae are small cavities called lacunae, which house cells called osteocytes. In addition, two large osteoclasts are seated on the outer edge of the outermost lamellae. The outermost lamellae are also surrounded by groups of small, white osteoblasts.
Figure 6.10
This illustration shows an anterior view of the right femur. The femur is split in half lengthwise to show its internal anatomy. The outer covering of the femur is the periosteum. Within it is a thin layer of compact bone that surrounds a central cavity called the medullary or marrow cavity. This cavity is filled with spongy bone at both epiphyses. A nutrient artery and vein travel through the periosteum and compact bone at the centre of the diaphysis. After entering the bone, the nutrient arteries and veins spread throughout the marrow cavity in both directions. Some of the arteries and veins in the marrow cavity also spread into the spongy bone within the distal and proximal epiphyses. However, additional blood vessels called the metaphyseal arteries and the metaphyseal veins enter into the metaphysis from outside of the bone.
Figure 6.11
Image A shows seven osteoblasts, which are cells with small, finger-like projections. They are surrounded by granules of osteoid. Both the cells and the osteoid are contained within a blue, circular, ossification centre that is surrounded by a “socket” of dark, string-like collagen fibres and gray mesenchymal cells. The cells are generally amorphous, similar in appearance to an amoeba. In image B, the ossification centre is no longer surrounded by a ring of osteoblasts. The osteoblasts have secreted bone into the ossification centre, creating a new bone matrix. There are also five osteocytes embedded in the new bone matrix. The osteocytes are thin, oval-shaped cells with many finger-like projections. Osteoid particles are still embedded in the bony matrix in image B. In image C, the ring of osteoblasts surrounding the ossification centre has separated, forming an upper and lower layer of osteoblasts sandwiched between the two layers of mesenchyme cells. The mesenchyme cells and the surrounding collagen fibres form the periosteum. The osteoblasts secrete spongy bone into the space between the two osteoblast rows. Therefore, the accumulating spongy bone pushes the upper and lower rows of osteoblasts away from each other. In this image, most of the spongy bone has been secreted by the osteoblasts, as the trabeculae are visible. In addition, an artery has already broken through the periosteum and invaded the spongy bone. Image D looks similar to image C, except that the rows of osteoblasts are now secreting layers of compact bone between the spongy bone and the periosteum. The artery has now branched and spread throughout the spongy bone. The cavities between the trabeculae now contain red bone marrow.
Figure 6.12
Image A shows a small piece of hyaline cartilage that looks like a bone but without the characteristic enlarged ends. The hyaline cartilage is surrounded by a thin perichondrium. In image B, the hyaline cartilage has increased in size, and the ends have begun to bulge outward. A group of dark granules forms at the centre of the cartilage. This is the calcified matrix, as opposed to the rest of the cartilage, which is uncalcified matrix. In image C, the hyaline cartilage has again increased in size, and spongy bone has formed at the calcified matrix. This is now called the primary ossification centre. A nutrient artery has invaded the ossification centre and is growing through the cavities of the new spongy bone. In image D, the cartilage now looks like a bone, as it has greatly increased in size and each end has two bulges. Only the proximal half of the bone is shown in all the remaining images. Spongy bone has completely developed in the medullary cavity, which is surrounded, on both sides, by compact bone. Now, the calcified matrix is located at the border between the proximal metaphysis and the proximal epiphysis. The epiphysis is still composed of uncalcified matrix. In image E, arteries and veins have now invaded the epiphysis, forming a calcified matrix at its centre. This is called a secondary ossification centre. In image F, the interior of the epiphysis is now completely calcified into bone. The outer edge of the epiphysis remains as cartilage, forming the articular cartilage at the joint. In addition, the border between the epiphysis and the metaphysis remains uncalcified, forming the epiphyseal plate.
Figure 6.13
This illustration shows a left-to-right progression of bone repair. The break is shown in the leftmost image, where the femur has an oblique, closed fracture in the middle of its shaft. The next image magnifies the break, showing that blood has filled the area between the broken bones. Blood has also filled in around the lateral and medial sides of the break. The influx of blood causes the broken area to swell, creating a hematoma. In the next image, the hematoma has been replaced with an external callus between the two broken ends. Within the internal callus, the blood vessels have reconnected, and some spongy bone has regenerated in the gap between the two bone halves. In the next image, spongy bone has completely regenerated, connecting the two broken ends, referred to as the bony callus. The external callus still remains on the lateral and medial sides of the break, as the compact bone has not yet regenerated. In the next image, the compact bone has fully regenerated, encapsulating the bony callus and completely reconnecting the two bone halves. The bone has a slight bulge at the location of the healed fracture, which is clearly shown in the final image, which shows a zoomed-out image of the completely healed femur.
Figure 6.14
This illustration resembles a flowchart. It begins with the sun shining on a silhouette of a man. One arrow leads from the sun to the man’s skin, stating that vitamin D is synthesized in the skin after the absorption of sunlight. Another arrow points into the man’s mouth and states that vitamin D is ingested through food and supplements, absorbed by the intestines, and carried to the liver via the bloodstream. A callout on the liver states that in the liver, vitamin D turns into 25 (OH) D, also known as calcidiol, the primary form of circulating vitamin D. Another callout on the right kidney states that in the kidneys, vitamin D is transformed into 1,25 (OH) D2. This is also known as calcitriol, a biologically active form of vitamin D. The synthesis of vitamin D facilitates calcium absorption from the small intestine, calcium reabsorption from the kidneys, and the rebuilding of bone tissue.
Figure 7.1
The figure shows the anterior (front) and posterior (back) views of the human skeleton. The axial skeleton is beige; the appendicular skeleton is green. The bones are grouped into major regions of the body as follows: The skull is the cranial portion and facial portion; the pectoral (shoulder) girdle is the clavicle and scapula; the thoracic cage is the sternum and ribs; the spine/core is the vertebral column and pelvic girdle (hip bones); the upper limbs are the humerus, ulna, radius, carpals, metacarpals, and phalanges; and the lower limbs are the femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges.
Figure 7.3
The figure shows the anterior (front) view of the skull with labelled bones and openings. The bones and features are grouped as follows: The cranial bones are the frontal bone, parietal bone, sphenoid bone, temporal bone, and ethmoid bone; the sutures and landmarks are the coronal suture and glabella; the orbital region is the orbit, optic canal, superior orbital fissure, inferior orbital fissure, supraorbital foramen, supraorbital margin, and lacrimal bone; the nasal region is the nasal bone, palatine bone, perpendicular plate of ethmoid bone, vomer bone, middle nasal concha, and inferior nasal concha; and the facial bones are the zygomatic bone, maxilla, alveolar process of maxilla, mental foramen, alveolar process of mandible, and mandible.
Figure 7.4
The figure shows the right lateral (side) view of the skull with labelled bones, sutures, and landmarks. The bones and features are grouped as follows: The cranial bones are the frontal bone, parietal bone, temporal bone, occipital bone, sphenoid bone (greater wing), and ethmoid bone; the sutures are the coronal suture, squamous suture, and lambdoid suture; the temporal bone features are the squamous temporal, zygomatic process, external acoustic meatus, mastoid portion, styloid process, mastoid process, articular tubercle, and mandibular fossa; the facial bones and features are the lacrimal bone, lacrimal fossa, nasal bone, zygomatic bone, temporal process, maxilla, mandible, and mental protuberance of the mandible; and additional landmarks are the zygomatic arch and pterion.
Figure 7.7
The figure shows the inferior (bottom-up) and superior (top-down) views of the base of the skull, with inset diagrams of a skull indicating the viewing angles. The upper panel is the inferior view and labels the following bones and structures: maxilla (palatine process), zygomatic bone, palatine bone (horizontal plate), vomer, medial and lateral pterygoid plates, zygomatic arch, sphenoid bone, articular tubercle, mandibular fossa, external auditory meatus, mastoid process, styloid process, stylomastoid foramen, entrance to carotid canal, foramen ovale, foramen spinosum, foramen lacerum, jugular foramen, temporal bone, occipital condyle, foramen magnum, occipital bone, superior nuchal line, and external occipital protuberance. The lower panel is the superior view and labels the following bones and structures: frontal bone, ethmoid bone (crista galli and cribriform plate), sphenoid bone (lesser wing and hypophyseal fossa—sella turcica), superior orbital fissure, foramen rotundum, foramen ovale, foramen spinosum, foramen lacerum and exit of carotid canal, internal acoustic meatus, jugular foramen, hypoglossal canal, temporal bone (petrous portion / petrous ridge), occipital bone, foramen magnum, and parietal bone.
Figure 7.9
The figure shows the superior (top-down) and posterior (back) views of the sphenoid bone with an inset image of a skull highlighting the sphenoid bone in yellow to indicate its location. The upper panel is the superior view and labels the following bones and structures: greater wing, lesser wing, body of sphenoid, hypophyseal fossa of sella turcica, optic canal, superior orbital fissure, foramen rotundum, foramen ovale, and foramen spinosum. The lower panel is the posterior view and labels the following bones and structures: greater wing, lesser wing, body of sphenoid, superior orbital fissure, and pterygoid plates.
Figure 7.10
The figure shows a midsagittal section of the skull with labelled bones and structures. The following bones and features are indicated: parietal bone, temporal bone, internal acoustic meatus, hypoglossal canal, occipital bone, styloid process, medial and lateral pterygoid plates, mandibular foramen, lingula, mylohyoid line, mandible, hyoid bone, palatine bone, maxilla, vomer, inferior nasal concha, sphenoid bone, sphenoid sinus, nasal bone, perpendicular plate, cribriform plate, crista galli, frontal sinus, and sella turcica (hypophyseal fossa).
Figure 7.20
The figure shows the superior view of a single vertebra and the left posterolateral view of articulated vertebrae with labelled features. The superior view labels the following structures: spinal cord, vertebral foramen, facet of superior articular process, facet for head of rib, spinous process, transverse process, vertebral arch (lamina and pedicle), and body. The left posterolateral view labels the following structures: spinal cord, facet of superior articular process, facet for head of rib, inferior articular process, spinous process, transverse process, intervertebral disc, body, vertebral arch (lamina and pedicle), and spinal nerve exiting through intervertebral foramen.
Figure 7.22
The figure shows multiple views of the cervical vertebrae with an inset image highlighting the cervical region of the spine in green. The upper left panel shows the structure of a typical cervical vertebra, labelling the spinous process (bifid), vertebral foramen, lamina, pedicle, superior articular process, transverse process, transverse foramen, body, and groove for spinal nerve. The upper right panel shows a lateral view of the cervical spine, labelling the dens of axis, transverse ligament, C1 (atlas), C2 (axis), C3, C7 (vertebra prominens), inferior articular process, bifid spinous process, and transverse process. The lower left panel shows a superior view of the atlas, labelling the dens, superior articular facet, transverse foramen, transverse process, ligament, anterior arch, and posterior arch. The lower middle panel shows a superior view of the axis, labelling the dens, superior articular facet, transverse foramen, transverse process, lamina, and spinous process. The lower right panel shows an anterior view of the axis, labelling the dens, transverse process, inferior articular process, and body.
Figure 7.27
The figure shows the anterior views of the sternum and the skeleton of the thorax. The left panel shows the sternum with the following structures labelled: clavicular notch, jugular notch, manubrium, sternal angle, body, and xiphoid process. The right panel shows the anterior skeleton of the thorax with the following structures labelled: clavicular notch, clavicle, scapula, jugular notch, sternum (manubrium, body, and xiphoid process), sternal angle, costal cartilages, intercostal space, and thoracic vertebrae T11 and T12, with ribs numbered, from top to bottom, 1 to 12.
Figure 8.1
The figure shows the anterior (front) and posterior (back) views of the human skeleton. The axial skeleton is beige; the appendicular skeleton is green. The bones are grouped into major regions of the body as follows: The skull is the cranial portion and facial portion; the pectoral (shoulder) girdle is the clavicle and scapula; the thoracic cage is the sternum and ribs; the spine/core is the vertebral column and pelvic girdle (hip bones); the upper limbs are the humerus, ulna, radius, carpals, metacarpals, and phalanges; and the lower limbs are the femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges.
Figure 8.2
The figure shows multiple views of the pectoral girdle and clavicle. The top left panel shows an anterior view of the pectoral girdle, labelling the coracoclavicular ligament, acromioclavicular joint, glenohumeral joint, scapula, clavicle, and costoclavicular ligament. The top right panel shows a posterior view of the pectoral girdle, labelling the clavicle, scapula, ribs, and vertebrae. The bottom panels show the clavicle, with the superior view labelling the acromial end (lateral) and sternal end (medial) and the inferior view showing the same ends with anterior and posterior orientation indicated.
Figure 8.3
The figure shows the anterior and posterior aspects of the right scapula with an inset image indicating its location in the pectoral girdle. The anterior aspect labels the following structures: acromion, coracoid process, glenoid cavity, suprascapular notch, superior border, superior angle, lateral border, medial border, and inferior angle. The posterior aspect labels the following structures: acromion, coracoid process, glenoid cavity, suprascapular notch, spine, supraspinous fossa, infraspinous fossa, subscapular fossa, lateral border, medial border, and inferior angle.
Figure 8.4
The figure shows the anterior and posterior views of the right humerus with an inset image indicating its location in the skeleton. The anterior view labels the following structures: humerus, head, anatomical neck, surgical neck, greater tubercle, lesser tubercle, intertubercular groove (sulcus), deltoid tuberosity, body (shaft), lateral supracondylar ridge, radial fossa, capitulum, head of radius, medial epicondyle, trochlea, and coronoid process of ulna. The posterior view labels the following structures: greater tubercle, anatomical neck, deltoid tuberosity, body (shaft), lateral epicondyle, olecranon fossa, coronoid fossa, medial epicondyle, olecranon of ulna, and head of radius.
Figure 8.5
The figure shows the anterior and posterior views of the right forearm with an inset image indicating its location in the skeleton. The anterior view labels the following structures: radius, ulna, radial notch of the ulna, head of radius, neck of radius, radial tuberosity, olecranon process, trochlear notch, coronoid process, proximal radioulnar joint, interosseous membrane, ulnar notch of the radius, distal radioulnar joint, head of ulna, styloid process of ulna, and styloid process of radius. The posterior view labels the following structures: radius, ulna, head of radius, neck of radius, and olecranon process.
Figure 8.6
The figure shows the anterior and posterior views of the left hand with an inset image indicating the location of carpals, metacarpals, and phalanges in the right hand. The anterior view labels the following structures: thumb (pollex), index finger, middle finger, ring finger, little finger, phalanges (distal and proximal), metacarpals (1 to 5), carpals (trapezium, trapezoid, scaphoid, hamate, capitate, pisiform, triquetrum, and lunate), radius, and ulna. The posterior view labels the following structures: phalanges (proximal, middle, and distal), metacarpals (1 to 5; with head, shaft, and base), carpals (trapezium, trapezoid, scaphoid, hamate, capitate, pisiform, triquetrum, and lunate), radius, and ulna.
Figure 8.9
The figure shows the lateral and medial views of the right hip bone with an inset image indicating the location of the pelvic girdle. The lateral view labels the following structures: ilium, iliac crest, posterior superior iliac spine, posterior inferior iliac spine, greater sciatic notch, ischial body, ischial spine, lesser sciatic notch, ischium, obturator foramen, ischial tuberosity, ischial ramus, ischiopubic ramus, anterior superior iliac spine, anterior inferior iliac spine, acetabulum, arcuate line, superior ramus of pubis, pubic tubercle, pubic body, and articular surface of pubis (at pubic symphysis). The medial view labels the following structures: ilium, iliac fossa, posterior superior iliac spine, posterior inferior iliac spine, auricular surface, greater sciatic notch, ischial spine, lesser sciatic notch, obturator foramen, ischium, ischial ramus, ischiopubic ramus, and pubis.
Figure 8.12
The figure shows the anterior and posterior views of the right femur with an inset image indicating its location in the skeleton. The anterior view labels the following structures: hip bone, femur, head, neck, greater trochanter, intertrochanteric line, lesser trochanter, body (shaft), lateral epicondyle, medial epicondyle, adductor tubercle, patella, tibia, and fibula. The posterior view labels the following structures: hip bone, femur, head, neck, greater trochanter, intertrochanteric crest, gluteal tuberosity, linea aspera, body (shaft), lateral epicondyle, medial epicondyle, intercondylar fossa, lateral condyle, tibia, and fibula.
Figure 8.13
The figure shows the anterior and posterior views of the right leg with an inset image indicating the location of the tibia and fibula. The anterior view labels the following structures: lateral condyle, medial condyle, tibial tuberosity, anterior border, interosseous membrane, tibia, fibula, medial malleolus, lateral malleolus, and articular surface. The posterior view labels the following structures: articular surface of medial condyle, articular surface of lateral condyle, head of fibula, soleal line, tibia, fibula, medial malleolus, and lateral malleolus.
Figure 8.14
The figure shows the superior, medial, and lateral views of the right foot with an inset image indicating the locations of tarsals, metatarsals, and phalanges. The superior view labels the following: distal phalanges, middle phalanges, proximal phalanges, metatarsals (1 to 5), medial cuneiform, intermediate cuneiform, lateral cuneiform, navicular, cuboid, talus, trochlea of talus, and calcaneus. The medial view labels the following: first metatarsal, medial cuneiform, intermediate cuneiform, navicular, talus, facet for medial malleolus, sustentaculum tali (talar shelf), calcaneus, and calcaneal tuberosity. The lateral view labels the following: fifth metatarsal, lateral cuneiform, intermediate cuneiform, navicular, cuboid, calcaneus, facet for lateral malleolus, and talus.
Figure 9.8
The figure shows a sagittal section of the knee joint highlighting key internal structures. The femur (upper bone) and tibia (lower bone) are shown with the patella (kneecap) anteriorly. The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) cross within the joint, stabilizing it. The synovial cavity is visible between the articular surfaces. Surrounding structures include the tendon of quadriceps femoris, patellar ligament, and infrapatellar fat pad. Three bursae are labelled: suprapatellar bursa, prepatellar bursa, and infrapatellar bursa, which reduce friction during movement.
Figure 9.9
The figure shows the six major types of synovial joints, each paired with its location in the human skeleton. The pivot joint, shown between the C1 and C2 vertebrae, allows rotational movement around a single axis. The hinge joint, shown at the elbow, permits flexion and extension. The saddle joint, located between the trapezium carpal bone and the first metacarpal bone, enables biaxial movement, including opposition of the thumb. The plane joint, located between tarsal bones, allows gliding movements. The condyloid joint, shown between the radius and carpal bones of the wrist, allows movement but no rotation. The ball-and-socket joint, shown at the hip, allows movement in multiple planes, including rotation. Each joint type is illustrated with an inset diagram showing its articular surfaces and permitted motions with arrows.
Figure 9.10
This figure highlights angular and rotational movements across major body regions. Two side-view male figures demonstrate flexion (bending) and extension (straightening) at the shoulder and knee joints, with arrows indicating the direction of movement. A head in profile shows flexion (chin toward chest) and extension (head tilting back), while a male torso bends forward and backward to show flexion and extension of the vertebral column. A frontal view shows abduction (arms moving away from the midline), adduction (arms moving toward the midline), and circumduction (arms moving in a circular path). Rotation is shown with arrows around the head and leg, indicating the head turning left and right and medial (inward) and lateral (outward) rotation of the thigh using the foot as a reference point.
Figure 9.11
Illustration showing additional types of body movements with arrows indicating the direction of movement for each action. A pair of forearms demonstrates pronation (palm facing downward as the radius crosses over the ulna) and supination (palm facing upward with the radius and ulna parallel). Feet illustrate dorsiflexion (toes pointing upward) and plantar flexion (toes pointing downward) as well as inversion (sole turning medially) and eversion (sole turning laterally). A side view of a male head and shoulders demonstrates protraction (jutting the mandible forward) and retraction (pulling the mandible backward) as well as elevation (closing the jaw) and depression (opening the jaw). A hand demonstrates opposition, with the thumb touching the tip of another finger.
Figure 9.13
Detailed cross-sectional illustration of the shoulder joint showing the articulation between the head of the humerus and the glenoid cavity of the scapula. The articular cartilage covering the joint surfaces and the glenoid labrum deepening the cavity are highlighted. The articular capsule is labelled with its synovial and fibrous membranes. Surrounding structures include the clavicle, acromion of the scapula, acromioclavicular and coracoacromial ligaments, and the subacromial bursa. The tendon of the supraspinatus muscle passes superiorly over the joint, and the tendon of the long head of the biceps brachii runs through the joint space within a tendon sheath.
Figure 9.14
Labelled diagrams of the elbow joint showing three views. Panel A, a medial sagittal section through the right elbow in lateral view, labels the humerus, fat pad, tendon of triceps muscle, bursa, trochlea, articular cartilage of the trochlear notch, olecranon bursa, articular capsule, synovial membrane, synovial cavity, articular cartilage of trochlea, tendon of brachialis muscle, ulna, and coronoid process. Panel B, a lateral view of the right elbow joint, labels the humerus, lateral epicondyle, radius, annular ligament, radial collateral ligament, ulna, olecranon process, and articular capsule. Panel C, a medial view of the left elbow joint, labels the articular capsule, annular ligament, ulnar collateral ligament, radius, ulna, and coronoid process.
Figure 9.15
Sagittal section and anterior views of the knee joint showing bones, ligaments, and cartilage that stabilize the joint; also, the superior view of the right tibia joint surface details the menisci and the cruciate ligaments. The sagittal view highlights the quadriceps tendon attaching to the patella, the patellar ligament connecting the patella to the tibial tuberosity, and the medial and lateral menisci between the femoral and tibial condyles. Collateral ligaments are labelled on both sides: the fibular (lateral) collateral ligament and the tibial (medial) collateral ligament. The superior view details with a light-gray colour the anterior cruciate ligament and posterior ligament and with a light-blue colour the articular cartilage on both medial and lateral condyles and medial and lateral menisci. The anterior view shows the muscles (quadriceps femoris), tendons (tendon of quadriceps femoris and lateral and medial patellar retinaculum), and ligaments (fibular and tibial collateral and patellar) that surround the knee joint.
Figure 10.1
This figure shows three micrographs, each depicting one of the three muscle tissues. Picture A shows skeletal muscle tissue, which is dense strips of pink tissue. Many small nuclei are dispersed throughout the tissue. The nuclei are flat and elongated, with multiple nuclei clustered into each cell. Picture B shows smooth muscle, which is densely packed and looks similar to skeletal muscle except that each cell only has one oval-shaped nucleus. Picture C shows cardiac muscle. Unlike skeletal and smooth muscle cells, cardiac muscle cells are not densely packed. The cardiac cells are branched, creating a large amount of space between each muscle cell.
Figure 10.2
Diagram showing the structural organization of skeletal muscle from the largest to the smallest components. The whole skeletal muscle is surrounded by the epimysium and is composed of multiple bundles called fascicles. Each fascicle is encased in perimysium and contains multiple muscle fibres (cells) surrounded by endomysium. A muscle fibre is a long cylindrical cell with a sarcolemma (cell membrane) and contains many myofibrils, which are the contractile elements. A satellite cell is shown on the periphery of the muscle fibre, associated with repair and growth. Arrows indicate the progressive magnification from the whole muscle to the myofibril level.
Figure 10.3
Diagram showing the microscopic anatomy of a skeletal muscle fibre and its myofibrils. The top portion depicts a cylindrical muscle fibre with multiple nuclei at the periphery, a sarcolemma (cell membrane), mitochondria, and parallel myofibrils. Light I bands and dark A bands are visible, giving the fibre a striated appearance. The bottom portion magnifies a single myofibril, showing repeating sarcomeres as the functional contractile units. Each sarcomere is bounded by Z discs and contains thin actin filaments and thick myosin filaments. The I band corresponds to regions with only thin filaments, the A band spans the length of the thick filaments, the H zone is the central region with only thick filaments, and the M line runs down the centre. The sarcoplasmic reticulum is shown surrounding the myofibril, storing and releasing calcium for contraction.
Figure 10.4
Detailed diagram of a sarcomere, the contractile unit of a muscle fibre, showing its structural components and molecular arrangement. The central image displays a sarcomere bounded by Z lines, with thin actin filaments extending from the Z lines and thick myosin filaments positioned centrally. The lighter I bands flank the sarcomere edges, while the darker A band spans the length of the thick filaments. The H zone, in the centre, contains only thick filaments, with the M line running through the middle anchoring them. Insets highlight molecular details: On the left, a portion of a thick filament is shown with projecting myosin heads; below it, a myosin molecule is illustrated with its twisted tail, flexible hinge region, heads, ATP-binding sites, and actin-binding sites. On the right, a portion of a thin filament is shown, made of actin subunits with binding sites for myosin, tropomyosin strands covering these sites, and troponin complexes positioned along the filament.
Figure 10.5
Diagram of a neuromuscular junction showing how a motor neuron stimulates a muscle fibre. At the top, a motor neuron with a myelin sheath surrounding the axon branches into axon terminals that form synaptic end bulbs at the neuromuscular junction on a skeletal muscle fibre. The muscle fibre is labelled with sarcolemma, sarcoplasm, and myofibrils. A zoomed view shows the synaptic end bulb above the muscle cell membrane, with synaptic vesicles containing acetylcholine. A nerve impulse or action potential reaches the synaptic end bulb, causing vesicles to release acetylcholine by exocytosis into the synaptic cleft. In the lower magnified view, acetylcholine diffuses across the synaptic cleft and binds to acetylcholine receptors on the motor end-plate of the sarcolemma. Binding opens ion channels, allowing sodium ions to enter the muscle cell, initiating muscle fibre activation.
Figure 10.7
Diagram illustrating the sequence of events in excitation-contraction coupling. At the top, a motor neuron delivers an action potential to the neuromuscular junction, causing a release of acetylcholine (ACh) into the synaptic cleft. ACh binds to receptors on the muscle fibre’s sarcolemma, opening sodium ion channels and triggering a new action potential that propagates along the sarcolemma and down the T-tubules. This leads to calcium release from the sarcoplasmic reticulum into the sarcoplasm. Calcium binds to troponin on the thin filaments, shifting tropomyosin and exposing actin’s myosin-binding sites. This allows myosin heads to form cross-bridges with actin, powered by ATP hydrolysis, leading to filament sliding and muscle fibre shortening. The diagram concludes with a depiction of the whole muscle contracting and generating tension.
Figure 10.10
Diagram illustrating the cross-bridge cycle of muscle contraction in five steps. First, calcium ions bind to troponin, exposing actin’s myosin-binding sites. Second, the myosin head, carrying ADP and Pi, forms a cross-bridge with actin. Third, the myosin head pivots, pulling the thin filament toward the M line as ADP and Pi are released. This is called the power stroke. Fourth, ATP binds to the myosin head, causing it to detach from actin. Fifth, ATP is hydrolyzed to ADP and Pi, recocking the myosin head to its high-energy position, ready for another cycle.
Figure 10.12
Graph showing the relationship between sarcomere length (x-axis, as a percentage of resting length) and muscle tension (y-axis, as a percentage of maximum). Tension rises steeply from near zero at about 60% sarcomere length, reaching a plateau at maximum tension between about 100% and 120% length, then declines as sarcomere length increases, falling back to zero near 170%. Illustrations below the x-axis depict sarcomeres at different lengths: Short sarcomeres show overlapping filaments (decreased length), optimal length shows ideal cross-bridge overlap, and very stretched sarcomeres show minimal overlap and no cross-bridges.
Figure 11.2
Composite diagram of skeletal muscle fascicle arrangements, each panel naming the pattern and an example muscle. Circular (sphincter) fibres encircle an opening; an inset highlights orbicularis oris around the mouth, which constricts the oral opening when it contracts. Parallel non-fusiform fibres run along the long axis (sartorius). Parallel-fusiform has a thick belly and tapered ends (biceps brachii). Convergent has a broad origin that fans into a single tendon (pectoralis major). Unipennate fibres attach to one side of a central tendon (extensor digitorum). Bipennate fibres attach to both sides of a central tendon (rectus femoris). Multipennate consists of several tendons in bundles (deltoid).
Figure 11.3
Anterior and posterior views of the human body showing major skeletal muscles, with the right side of each view showing superficial muscles and the left side showing deeper muscles. In the anterior superficial view, labelled muscles include frontalis, orbicularis oculi, zygomaticus, orbicularis oris, sternocleidomastoid, deltoid, pectoralis major, biceps brachii, brachialis, brachioradialis, flexor carpi radialis, sartorius, quadriceps femoris group (rectus femoris, vastus lateralis, and vastus medialis), tibialis anterior, and fibularis longus. In the anterior deep view, labelled muscles include temporalis, masseter, platysma, pectoralis minor, serratus anterior, external oblique, transversus abdominis, flexor digitorum superficialis, adductor longus, gracilis, and gastrocnemius. In the posterior superficial view, labelled muscles include trapezius, deltoid, triceps brachii, latissimus dorsi, gluteus medius, gluteus maximus, hamstrings (biceps femoris and semitendinosus), gastrocnemius, soleus, and calcaneal (Achilles) tendon. In the posterior deep view, labelled muscles include splenius capitis, levator scapulae, rhomboid major, infraspinatus, teres major, teres minor, external oblique, gluteus minimus, adductor magnus, and fibularis longus.
Figure 11.6
The image shows a labelled anterior view of the neck with muscles, bones, and other structures identified. At the top, the inferior edge of the mandible is labelled. The suprahyoid muscles are listed on the right and include the geniohyoid, digastric, mylohyoid, and stylohyoid. The styloglossus muscle is labelled near the upper neck. The hyoid bone is labelled in the mid-neck region. The infrahyoid muscles are listed on the right and include the thyrohyoid, omohyoid, sternohyoid, and sternothyroid. The thyroid cartilage of the larynx, thyroid gland, and trachea are labelled along the midline of the neck. At the base of the neck, the right and left clavicles, sternum, and scapula are labelled.
Figure 11.7
The image shows three labelled views of the neck muscles. The left panel shows a left lateral view with the splenius capitis, sternocleidomastoid, levator scapulae, trapezius, acromion process of scapula, and scalenes labelled. The middle panel shows a posterior view of the superficial neck muscles with the right trapezius removed, labelling the levator scapulae and multifidus muscles as well as the first thoracic vertebrae. A boxed region highlights the location of the suboccipital muscles. The right panel shows a posterior view of the deep neck muscles with the left semispinalis capitis removed, labelling the suboccipital muscles, splenius capitis (cut), longissimus capitis, and semispinalis capitis.
Figure 11.8
The image shows four labelled views of the muscles of the neck and back. The top left panel shows a left lateral view of the neck with the levator scapulae, sternocleidomastoid, splenius, trapezius, medial scalene, anterior scalene, and clavicle labelled. The top right panel shows a posterior view with the superficial left-side and deep right-side muscles of the neck and upper back labelled, including the trapezius, splenius capitis, splenius cervicis, rhomboides minor, and rhomboides major. The bottom left panel shows a posterior view of the deep muscles of the back, labelling the semispinalis capitis (joined with deep spinalis capitis), semispinalis cervicis, longissimus cervicis, spinalis thoracis, semispinalis thoracis, multifidus, longissimus capitis, iliocostalis cervicis, iliocostalis thoracis, longissimus thoracis, and iliocostalis lumborum. The bottom right inset shows the deep spinal muscles with the multifidus removed, labelling the transverse processes of the vertebrae, rotator brevis, rotator longus, interspinales, short rotator, and intertransversarii.
Figure 11.9
The image shows two labelled views of the abdominal muscles. Panel A shows an anterior lateral view of the superficial and deep abdominal muscles. The labelled superficial structures include the pectoralis major, latissimus dorsi, anterior serratus muscles, external oblique, linea alba of the rectus sheath, rectus abdominis (enclosed within the rectus sheath), and tendinous intersections between the anterior segments of the rectus abdominis. A magnified inset highlights the deep abdominal muscles and connective tissue, labelling the rectus sheath, transversus abdominis, internal oblique, aponeurosis of the internal oblique, and external oblique. Panel B shows an anterior view of the posterior abdominal muscles, labelling the quadratus lumborum, sacrum, ilia of the hip bones, iliacus, and psoas major.
Figure 11.10
The image shows an inferior view of the diaphragm with labelled anatomical structures. The central tendon of the diaphragm is shown in the middle. The diaphragm itself is labelled along the periphery. The sternum is labelled at the top, and the vertebrae are labelled at the bottom. Openings through the diaphragm are labelled, including the vena cava passing through the caval opening, the esophagus passing through the esophageal hiatus, and the aorta passing through the aortic hiatus. The 12th (floating) ribs are labelled on each side. The left psoas major and left quadratus lumborum muscles are labelled along the lower lateral edge of the figure.
Figure 11.11
The image shows two labelled views of the thoracic wall and intercostal muscles. The left panel shows the anterior thoracic wall with the pectoralis major dissected to reveal underlying structures. Labelled features include the clavicle, ribs, sternum, pectoralis minor, serratus anterior, internal intercostals, and external intercostals. A boxed region highlights the intercostal space. The right panel is an enlarged view of the intercostal space, showing the layering of the external intercostal, internal intercostal, and innermost intercostal muscles between two ribs.
Figure 11.13
The image shows four labelled views of the muscles of the left shoulder. Panel A shows a left anterior lateral view with the pectoralis major and latissimus dorsi labelled. Panel B shows a posterior view with the left deltoid and left latissimus dorsi labelled. Panel C shows an anterior lateral view of the deep muscles of the left shoulder, labelling the pectoralis major (cut), deltoid (cut), coracoid process of the scapula, subscapularis, teres major, and serratus anterior. Panel D shows a posterior view of the deep muscles of the left shoulder, labelling the teres minor, supraspinatus, spine of the scapula, deltoid (cut), infraspinatus, teres major, latissimus dorsi near its origin, humerus, triceps brachii long head, and triceps brachii lateral head.
Figure 11.14
The image shows six labelled views of the muscles of the left upper arm and forearm. The top left panel shows an anterior lateral view of the left upper arm, labelling the biceps brachii short head, biceps brachii long head, and brachialis. The top right panel shows a posterior view of the left upper arm, labelling the triceps brachii lateral head and triceps brachii long head. The middle left panel shows the superficial muscles of the left forearm in palmar view, labelling the biceps brachii, brachioradialis, pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis. The middle right panel shows the superficial muscles of the left forearm in dorsal view, labelling the triceps brachii, brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, anconeus, extensor carpi ulnaris, extensor digitorum, and extensor digiti minimi, along with the lateral epicondyle of the humerus. The bottom left panel shows the deep muscles of the left forearm in palmar view, labelling the brachialis (cut), flexor digitorum profundus, flexor retinaculum (cut), flexor pollicis longus, pronator quadratus, and medial and lateral epicondyles of the humerus. The bottom right panel shows the deep muscles of the left forearm in dorsal view, labelling the abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, extensor indicis, flexor digitorum profundus, extensor retinaculum, flexor carpi ulnaris, and medial epicondyle of the humerus.
Figure 11.15
The image shows three labelled views of the pelvic and thigh muscles of the right leg. The top panel shows an anterior view of the superficial pelvic and thigh muscles, labelling the quadratus lumborum, iliacus, crest of ilium, tensor fascia latae, rectus femoris, vastus lateralis, vastus medialis, quadriceps tendon (or patellar tendon), patellar ligament, psoas major, pectineus, sacrum, adductor longus, gracilis, adductor magnus, and sartorius. The bottom left panel shows an anterior view of the deep pelvic and thigh muscles, labelling the iliac crest, pubis, femur, pectineus, obturator externus, adductor brevis, adductor longus, and adductor magnus. The bottom right panel shows a posterior view of the pelvic and thigh muscles, labelling the crest of ilium, sacrum, gluteus medius (cut), gluteus minimus, piriformis, superior gemellus, inferior gemellus, obturator internus, obturator externus, quadratus femoris, biceps femoris, gluteus maximus (cut), adductor group, gracilis, semimembranosus, and semitendinosus.
Figure 11.16
The image shows three labelled views of the muscles of the right lower leg. The left panel shows an anterior view of the superficial muscles, labelling the tibialis anterior, fibularis longus, extensor digitorum longus, fibularis brevis, extensor hallucis longus, fibularis tertius, superior extensor retinaculum, and inferior extensor retinaculum. The middle panel shows a posterior view of the superficial muscles, labelling the gastrocnemius lateral head, gastrocnemius medial head, plantaris, soleus, calcaneal (Achilles) tendon, and calcaneus (heel). The right panel shows a posterior view of the deep muscles, labelling the popliteus, soleus (cut), fibularis longus, tibialis posterior, flexor digitorum longus, flexor hallucis longus, and fibularis brevis.
Figure 12.4
This illustration shows a superior view of a cross-section of the brain. The anterior side of the brain is at the top of the diagram, with the two eyes clearly visible. Each eye contains a left nerve tract and a right nerve tract. In the left eye, the left nerve tract travels straight back to the right side of the thalamus. It then enters the left occipital lobe. Conversely, the right nerve tract crosses to the right side of the brain through the optic chiasma. It travels through the right side of the thalamus and enters the right occipital lobe. In the right eye, the opposite is true. The left nerve tract crosses over to the left side of the brain at the optic chiasma, travelling into the left side of the thalamus and the left side of the occipital lobe. However, the right nerve tract leads straight back to the right side of the thalamus and the right occipital lobe. Therefore, the optic chiasma is where the right nerve tract from the right eye crosses over the left nerve tract from the left eye.
Figure 12.5
This illustration shows a silhouette of a human with only the brain, spinal cord, PNS ganglia, nerves, and a section of the digestive tract visible. The brain, which is part of the CNS, is the area of perception and processing of sensory stimuli (somatic/autonomic), the execution of voluntary motor responses (somatic), and the regulation of homeostatic mechanisms (autonomic). The spinal cord, which is part of the CNS, is the area where reflexes are initiated. The gray matter of the ventral horn initiates somatic reflexes, while the gray matter of the lateral horn initiates autonomic reflexes. The spinal cord is also the somatic and autonomic pathway for sensory and motor functions between the PNS and the brain. The nerves, which are part of the PNS, are the fibres of sensory and motor neurons, which can be either somatic or autonomic. The ganglia, which are part of the PNS, are the areas for the reception of somatic and autonomic sensory stimuli. These are received by the dorsal root ganglia and cranial ganglia. The autonomic ganglia are also the relay for visceral motor responses. The digestive tract is part of the enteric nervous system, the ENS, which is located in the digestive tract and is responsible for autonomous function. The ENS can operate independently of the brain and spinal cord.
Figure 12.6
This illustration shows the anatomy of a neuron. The neuron has a very irregular cell body (soma) containing a purple nucleus. There are six projections protruding from the top, bottom, and left side of the cell body. Each of the projections branches many times, forming small, tree-shaped structures protruding from the cell body. The right side of the cell body tapers into a long cord called the axon. The axon is insulated by segments of myelin sheath, which resemble a semitransparent toilet paper roll wound around the axon. The myelin sheath is not continuous but is separated into equally spaced segments. The bare axon segments between the sheath segments are called nodes of Ranvier. An oligodendrocyte is reaching its two armlike projections onto two myelin sheath segments. The axon branches many times at its end, where it connects to the dendrites of another neuron. Each connection between an axon branch and a dendrite is called a synapse. The cell membrane completely surrounds the cell body, dendrites, and axon. The axon of another nerve is seen in the upper left of the diagram, connecting with the dendrites of the central neuron.
Figure 12.7
Three illustrations show some of the possible shapes that neurons can take. In the unipolar neuron, the dendrite enters from the left and merges with the axon into a common pathway, which is connected to the cell body. The axon leaves the cell body through the common pathway, then branches off to the right, in the opposite direction as the dendrite. Therefore, this neuron is T-shaped. In the bipolar neuron, the dendrite enters the left side of the cell body, while the axon emerges from the opposite (right) side. In a multipolar neuron, multiple dendrites enter the cell body. The only part of the cell body that does not have dendrites is the part that elongates into the axon.
Figure 12.8
This diagram contains three black-and-white drawings of more specialized nerve cells. Part A shows a pyramidal cell of the cerebral cortex, which has two long nerve tracts attached to the top and bottom of the cell body. However, the cell body also has many shorter dendrites projecting out a short distance from the cell body. Part B shows a Purkinje cell of the cerebellar cortex. This cell has a single long nerve tract entering the bottom of the cell body. Two large nerve tracts leave the top of the cell body but immediately branch many times to form a large web of nerve fibres. Therefore, the Purkinje cell somewhat resembles a shrub or coral in shape. Part C shows the olfactory cells in the olfactory epithelium and olfactory bulbs. It contains several cell groups linked together. At the bottom, there is a row of olfactory epithelial cells that are tightly packed side by side, somewhat resembling the slats of a fence. There are six neurons embedded in this epithelium. Each neuron connects to the epithelium through branching nerve fibres projecting from the bottom of its cell body. A single nerve fibre projects from the top of each neuron and synapses with nerve fibres from the neurons above. These upper neurons are cross-shaped, with one nerve fibre projecting from the bottom, top, right, and left sides. The upper cells synapse with the epithelial nerve cells using the nerve tract projecting from the bottom of their cell bodies. The nerve tract projecting from the top continues the pathway, making a ninety-degree turn to the right and continuing to the right border of the image.
Figure 12.9
This diagram shows several types of nervous system cells associated with two multipolar neurons. Astrocytes are star-shaped cells with many dendrite-like projections but no axon. They are connected with the multipolar neurons and other cells in the diagram through their dendrite-like projections. Ependymal cells have a teardrop-shaped cell body and a long tail that branches several times before connecting with astrocytes and the multipolar neuron. Microglial cells are small cells with rectangular bodies and many dendrite-like projections stemming from their shorter sides. The projections are so extensive that they give the microglial cell a fuzzy appearance. The oligodendrocytes have circular cell bodies with four dendrite-like projections. Each projection is connected to a segment of myelin sheath on the axons of the multipolar neurons. The oligodendrocytes are the same colour as the myelin sheath segment and add layers to the sheath using their projections.
Figure 12.10
This diagram shows a collection of peripheral nervous system glial cells. The largest cell is a unipolar peripheral ganglionic neuron, which has a common nerve tract projecting from the bottom of its cell body. The common nerve tract then splits into the axon, going off to the left, and the dendrite, going off to the right. The cell body of the neuron is covered with several satellite cells that are irregular and flattened. Schwann cells wrap around each myelin sheath segment on the axon, with their nucleus creating a small bump on each segment.
Figure 12.11
This two-part diagram shows the process of myelination represented by three images and a micrograph. In the left image, the cell membrane of a cylindrical Schwann cell, which has a blue nucleus, is indented around an axon. The upper and lower lip of the cell membrane is visible where the membrane indents around the axon. In the middle image, the lower lip of the cell membrane dives under the upper lip and wraps around the axon. In the right image, the process in part B has continued, forming many layers of myelin that wrap around the axon. The nucleus of the Schwann cell is still visible in the outermost layer, just to the left of the upper lip. The area of the axon next to the Schwann cell, which has no myelin, is labelled as a node of Ranvier. The micrograph shows details of the inset on the right, representing a section through the axon labelling the axolemma, myelin sheet, external lamina, and endonerium (collagen).
Figure 12.12
This diagram shows the complete pathway a nerve impulse takes when a person tests the temperature of shower water with their hand. First, a sensory nerve ending in the index finger sends a nerve impulse to the spinal cord. A cross-section of one segment of the spinal cord is shown from a superior view. The sensory nerve connected to the nerve ending is located in the dorsal root ganglion. The nerve ending is a dendrite of the sensory neuron, as it also has an axon that synapses with an interneuron. The interneuron then synapses with a second interneuron in the thalamus. This second interneuron synapses with brain tissue in the cerebral cortex, allowing conscious perception of the water temperature. The brain then initiates a motor command by stimulating an upper motor neuron in the cerebral cortex. The axon of the upper motor neuron extends all the way to the spinal cord, where it synapses with a lower motor neuron in the gray matter of the spinal cord. The impulse then travels down the lower motor neuron back to the hand, where it synapses with the skeletal muscles of the hand. This triggers the muscle contractions that turn the dials of the shower to adjust the water temperature.
Figure 12.15
This diagram shows a cross-section of a cell membrane. The cell membrane proteins are large, blocky objects. Peripheral proteins are not embedded in the phospholipid bilayer. The peripheral protein shown here is attached to the outside surface of another protein on the extracellular fluid side. Integral proteins are embedded between the phospholipids of the cell membrane. The transmembrane integral protein extends through both phospholipid layers. The opposite ends of this protein project into the cytosol and the extracellular fluid. A second, smaller integral protein only extends into the inner phospholipid layer. Its opposite end projects into the cytosol. This second protein is, therefore, not a transmembrane protein. The channel protein is cylinder-shaped with a hollow internal tube labelled the pore. The sides of the channel protein can bulge inward to close the pore.
Figure 12.16
These two diagrams each show a channel protein embedded in the cell membrane. In the left diagram, there is a large number of sodium ions (Na plus) and calcium ions (Ca2 plus) in the extracellular fluid. Within the cytosol, there is a large number of potassium ions (K plus) but only a few sodium ions. In this diagram, the channel is closed. Two ACh molecules are floating in the extracellular fluid. Their label indicates that a neurotransmitter, a ligand, is required to open the ion channel. The neurotransmitter receptor site on the extracellular fluid side of the channel protein matches the shape of the ACh molecules. In the right diagram, the two ACh molecules attach to the neurotransmitter receptor sites on the channel protein. This opens the channel, and the sodium and calcium ions diffuse through the channel and into the cytosol, down their concentration gradient. The potassium ions also diffuse through the channel in the opposite direction down their concentration gradient (out of the cell and into the extracellular fluid).
Figure 12.17
These two diagrams each show a channel protein embedded in the cell membrane. In the left diagram, there is a large number of sodium ions in the extracellular fluid but only a few sodium ions in the cytosol. There is a large number of calcium ions in the cytosol but only a few calcium ions in the extracellular fluid. In this diagram, the channel is closed, as the extracellular side has a lid, somewhat resembling that on a trash can, that is closed over the channel opening. In the right diagram, the mechanically gated channel is open. This allows the sodium ions to flow from the extracellular fluid into the cell, down their concentration gradient. At the same time, the calcium ions are moving from the cytosol into the extracellular fluid, down their concentration gradient.
Figure 12.18
This is a two-part diagram. Both diagrams show a voltage-gated channel embedded in the lipid membrane bilayer. The channel contains a sphere-shaped gate that is attached to a filament. In the first diagram, there are several ions in the cytosol but only one ion in the extracellular fluid. The voltage across the membrane is currently negative 70 millivolts, and the voltage-gated channel is closed. In the second diagram, the voltage in the cytosol is negative 50 millivolts. This voltage change has caused the voltage-gated channel to open, as the small sphere is no longer occluding the channel. One of the ions is moving through the channel, down its concentration gradient, and out into the extracellular fluid.
Figure 12.19
This is a two-part diagram. Both diagrams show a leakage channel embedded in the lipid membrane bilayer. The leakage channel is cylindrical with a large, central opening. In the first diagram, there are several ions in the cytosol but only one ion in the extracellular fluid. No ions are moving through the leakage channel because the channel is closed. In the second diagram, the leakage channel randomly opens, allowing two ions to travel through the channel, down their concentration gradient, and out into the extracellular fluid.
Figure 12.22
This graph has membrane potential in millivolts on the y-axis, ranging from negative 70 to positive 30. Time is on the x-axis. In step one, which is labelled “at rest,” the plot line is steady at negative 70 millivolts. In step two, a stimulus is applied, causing the plot line to increase to positive 30 millivolts. The curve sharply increases at step three, labelled “voltage rises.” After peaking at positive 30, the plot line then quickly drops back to negative 70. This is the fourth step, labelled “voltage falls.” The plot line continues to drop below negative 70, and this is step five, labelled “end of action potential.” Finally, the plot line gradually increases back to negative 70 millivolts, which is step six, labelled “return to rest.”
Figure 12.23
The graph has membrane potential in millivolts on the y-axis, ranging from negative 90 millivolts to negative 40 millivolts. Time is on the x-axis. The left half of the plot line is labelled “depolarizing graded potential.” The plot has four progressively larger peaks, with each starting at the resting membrane potential of negative 70 millivolts. The lowest peak reaches about negative 65 millivolts and is narrow in width, as this represents a small stimulus that causes a small depolarization of the cell membrane. The second peak reaches about negative 60 millivolts but is still narrow. This represents a larger stimulus causing more depolarization. The third peak also reaches about negative 62 millivolts but is about twice as wide as the other two peaks. This represents a stimulus of longer duration, which causes a longer-lasting depolarization. However, this stimulus is not greater in strength than the previous stimulus. The rightmost peak among the depolarizing graded potentials reaches above the threshold line to about negative 52 millivolts. This represents a stimulus of sufficient strength to trigger an action potential (at negative 55 millivolts). The right half of the plot is labelled “hyperpolarizing graded potential.” The plot line in this half begins at the resting potential of negative 70 millivolts, then drops to more negative membrane potentials. The first peak drops to negative 75 millivolts, the second peak drops to negative 78 millivolts, and the third peak drops to negative 87 millivolts. These peaks represent a stimulus that results in hyperpolarization, which is triggered by the activation of specific ion channels in the cell membrane.
Figure 12.24
This graph has membrane potential in millivolts on the y-axis, ranging from negative 90 to positive 30. Time is on the x-axis. The plot line is moving up and down between the resting membrane potential of negative 70 millivolts and the threshold potential of negative 55 millivolts. An EPSP causes the plot line to move higher, closer to the threshold potential. An IPSP causes the plot line to move lower, farther away from the threshold potential. Toward the right side of the graph, the neuron receives an EPSP that pushes the membrane potential above the threshold, triggering an action potential that causes the plot line to quickly rise above positive 30 millivolts. The plot line then quickly drops back below negative 80 millivolts but then gradually increases back to negative 70 millivolts. A picture of a neuron indicates that excitatory postsynaptic potentials are commonly provided by synapses on the neuron’s dendrites. Inhibitory postsynaptic potentials are commonly provided by synapses near the neuron’s axon hillock.
Figure 12.25
This diagram shows a postsynaptic neuron. An axon from a presynaptic neuron is synapsing with the dendrites on the postsynaptic neuron. The axon of the presynaptic neuron branches into several club-shaped axon terminals. A magnified view of one of the synapses reveals that the axon terminal does not contact the dendrite of the postsynaptic neuron. Instead, there is a small space between the two structures, called the synaptic cleft. The axon terminal of the presynaptic neuron contains several synaptic vesicles, each holding about a dozen neurotransmitter particles. The synaptic vesicles travel to the edge of the axon terminal and release their neurotransmitters into the synaptic clefts. The neurotransmitters travel through the synaptic cleft and bind to carrier proteins on the postsynaptic neuron that contain receptors for neurotransmitters.
Figure 12.26
This diagram contains two images, labelled A and B. Both images show a cross-section of a postsynaptic membrane. There are two proteins embedded in each of the two membrane cross-sections. In diagram A, direct activation brings about an immediate response. Here, both of the membrane proteins are ion channels. Several hexagonal neurotransmitters bind to ionotropic receptors on the extracellular fluid side of the channels. The binding of neurotransmitters causes the channels to open, allowing ions to flow from the extracellular fluid into the cytosol. Image B shows indirect activation, which involves a prolonged response, amplified over time. Here, one of the cell membrane proteins is solid, while the other is a channel. Neurotransmitters bind to metabotropic receptors on the extracellular side of the solid protein. This triggers the solid protein to activate a G protein in the cytoplasm. The G protein binds to an effector protein in the cytoplasm, which results in the production of several second messenger particles. The second messenger activates enzymes that open the channel protein, allowing ions to enter the cytoplasm.
Figure 13.6
The image shows two views of the spinal cord in cross-section. The top panel is a labelled diagram showing gray matter and white matter regions. The gray matter is arranged in an H-shaped pattern, with the posterior (dorsal) horn, lateral horn, and anterior (ventral) horn labelled. The central canal is labelled at the centre. Surrounding the grey matter, the white matter is divided into posterior (dorsal) columns, lateral columns, and anterior (ventral) columns. The bottom panel shows a histological cross-section of the spinal cord, with the grey matter visible as a butterfly- or H-shaped region in the centre, surrounded by lighter-stained white matter.
Figure 13.7
The image shows a labelled diagram of the arteries of the brain, focusing on the circle of Willis and associated vessels. At the top, the anterior communicating artery connects the two anterior cerebral arteries. Branching laterally from the internal carotid artery are the middle cerebral artery, ophthalmic artery, and anterior choroidal artery. Posteriorly, the posterior communicating arteries connect to the posterior cerebral arteries. The basilar artery runs along the midline, giving off pontine arteries and the superior cerebellar arteries and continuing upward to join the posterior cerebral arteries. Inferiorly, the basilar artery is formed by the merging of the vertebral arteries, which also give off the anterior inferior cerebellar arteries and posterior inferior cerebellar arteries. The anterior spinal artery descends from the vertebral arteries along the midline.
Figure 13.8
The image shows a sagittal section of the head with the dural venous sinuses and cerebral veins labelled. The cranium and dura mater are labelled at the top. The superior sagittal sinus runs along the top midline, with cerebral veins draining into it. The inferior sagittal sinus runs below it and connects to the straight sinus, which continues posteriorly to the confluence of sinuses. The transverse sinus extends laterally from the confluence, and the occipital sinus descends toward the base of the skull. The great cerebral vein is shown draining into the straight sinus. The diagram also notes that blood returns to the jugular vein via the sigmoid sinus.
Figure 13.9
The image shows a cross-section of the meninges and superior sagittal sinus. The outermost layer is bone, followed by the dura mater. Beneath the dura is the subdural space and the arachnoid mater, with arachnoid granulation villi projecting into the superior sagittal sinus to allow cerebrospinal fluid drainage. The subarachnoid space lies below the arachnoid mater and contains arachnoid trabeculae. The pia mater closely follows the surface of the cerebral cortex. Cerebral veins drain blood into the superior sagittal sinus, which runs along the longitudinal fissure at the midline.
Figure 13.10
The image shows a sagittal section of the brain with the ventricular system and cerebrospinal fluid flow pathway labelled. The right lateral ventricle is shown connecting to the third ventricle via the interventricular foramen. The choroid plexus is labelled within the ventricles as the site of cerebrospinal fluid production. From the third ventricle, fluid passes through the cerebral aqueduct into the fourth ventricle. The fourth ventricle has a median aperture and lateral apertures through which fluid flows into the subarachnoid space. The central canal is labelled, showing the path of fluid into the spinal cord. The subarachnoid space surrounds the brain, and arachnoid granulations drain cerebrospinal fluid into the superior sagittal sinus, which is labelled at the top. The meningeal dura mater is also labelled, showing the outer protective covering of the brain.
Figure 13.11
The image shows two views of a spinal nerve and its connective tissue coverings. Panel A is a diagram illustrating the structure of a spinal nerve. It shows the entire spinal nerve surrounded by the epineurium, with blood vessels running through it. Inside the nerve, bundles of axons called fascicles are each surrounded by perineurium, while individual axons are wrapped in endoneurium. An enlarged cross-section highlights the arrangement of fascicles, perineurium, and axons. Panel B is a histological section of a spinal nerve stained pink, showing fascicles surrounded by perineurium and the entire nerve encased in epineurium.
Figure 13.13
The image shows the inferior view of the brain with all twelve cranial nerves labelled. The olfactory nerve (I) is seen at the most anterior end, followed by the optic nerve (II). The oculomotor nerve (III) and trochlear nerve (IV) are positioned slightly posterior to the optic chiasm. The trigeminal nerve (V) is shown branching laterally. The abducens nerve (VI), facial nerve (VII), and vestibulocochlear nerve (VIII) are arranged in sequence along the brain stem. Further posteriorly, the glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII) are labelled near the medulla and spinal cord region.
Figure 13.14
This image shows the major nerve plexuses and named peripheral nerves along the human torso and pelvis in an anterior view. The cervical plexus, arising from spinal nerves C1 to C5, is labelled at the top, along with the phrenic nerve. The brachial plexus, arising from C5 to T1, is shown branching into the axillary, median, radial, and ulnar nerves. Lower down, the lumbar plexus from L1 to L4 is labelled, with the femoral and obturator nerves indicated. The sacral plexus from L4 to S4 is shown giving rise to the sciatic nerve, which divides into the common fibular nerve and tibial nerve. The vertebral column is drawn in the centre for reference, with spinal nerve roots indicated along its length.
Figure 14.1
Diagram showing three types of sensory neurons and receptor structures. The first neuron has free nerve endings at the dendrites on one end, a long axon with myelin sheaths, and a cell body along the axon. It is labelled “Neuron (receptor) with free nerve endings.” The second neuron has dendrites enclosed in a capsule labelled “encapsulated nerve ending,” connected to an axon with myelin segments and a cell body along it. It is labelled “Neuron (receptor) with encapsulated nerve endings.” The third panel shows a rod photoreceptor cell connected to a bipolar cell. It has an elongated, cylindrical outer segment labelled “rod,” and the bipolar cell is shown receiving its signal.
Figure 14.3
Illustration showing the olfactory system and nasal cavity. The first panel depicts the nasal cavity with air entering through the nose and passing the nasal conchae toward the olfactory epithelium beneath the olfactory bulb. The second panel magnifies the olfactory region, showing olfactory neurons extending through the ethmoid bone to the olfactory bulb, where they connect with mitral cells in the olfactory tract. It also labels olfactory receptors, glands, cilia, and mucus, where odour molecules dissolve. A histological image at the bottom shows the layered olfactory epithelium in pink and purple staining.
Figure 14.4
Illustration showing the anatomy of the human ear in cross-section, divided into external, middle, and inner regions. The external ear includes the auricle and ear canal leading to the tympanic membrane (eardrum). The middle ear contains the ossicles—the malleus, incus, and stapes (attached to the oval window)—within the tympanic cavity. The inner ear features the cochlea, vestibule, and semicircular canals, connected to the vestibular and cochlear nerves. The round window and Eustachian tube are also labelled.
Figure 14.5
Diagram illustrating how sound waves are transmitted through the ear. A tuning fork generates waves representing alternating areas of high and low pressure. The tympanic membrane vibrates in response, and these vibrations are amplified by the ossicles in the middle ear. The stapes transmits vibrations through the oval window, creating standing waves in the vestibular fluid of the cochlea. Within the cochlea, the basilar membrane vibrates at frequency-specific points, stimulating hair cells in the organ of Corti. Insets show wave frequency and amplitude relationships.
Figure 14.9
Diagram illustrating how different sound frequencies are detected along the cochlea. The image shows the ear from the outer to the inner sections, with the cochlea expanded to display the basilar and tectorial membranes. High-frequency sounds (20,000 Hz) stimulate the base near the oval window, midrange frequencies (1,500 Hz) affect the middle, and low frequencies (20 Hz) reach the apex. A graph below shows that fibre length in the basilar membrane increases toward the apex, corresponding to lower frequencies.
Figure 14.10
Diagram showing how the maculae in the utricle and saccule detect head position and linear acceleration. The left side illustrates their location within the inner ear with an inset showing a close-up view of the endolymph, macula, otoliths, otolithic membrane, hair cells, and vestibular division of the vestibulocochlear nerve. On the right, two panels show a person’s head upright and tilted forward. When upright, otoliths rest evenly on the otolithic membrane above hair cells. When the head tilts, gravity shifts the otoliths, bending the hair cells and signalling a change in head position to the vestibular nerve.
Figure 14.13
Cross-sectional diagram of the human eye labelled with structures organized by region: External and outer structures include the lateral rectus muscle, medial rectus muscle, sclera, and cornea. Middle and vascular layers include the choroid, ciliary body, ciliary muscle, ciliary process, suspensory ligaments, iris, and pupil. Internal and neural layers include the retina, fovea centralis, optic disc (blind spot), optic (II) nerve, and central retinal artery and vein. Cavities and chambers include the anterior cavity, anterior chamber, posterior chamber, posterior cavity, vitreous chamber, and scleral venous sinus (canal of Schlemm).
Figure 14.14
Diagram and micrograph of the retina showing its layered structure and cell types. The diagram depicts photoreceptor cells, including rods and cones, with labelled parts such as pigment epithelium, melanin granules, connecting stalks, discs, mitochondria, Golgi apparatus, nuclei, bipolar cells, and ganglion cells, with light entering from below. The micrograph shows the corresponding histological layers: choroid, pigment epithelium, rods and cones, bipolar cells, ganglion cells, and optic nerve axons, with light passing through the layers toward the photoreceptors.
Figure 14.15
Diagram comparing the dorsal column system and spinothalamic tract pathways for sensory transmission. On the left, the dorsal column system carries fine touch and proprioception sensations from the right side of the body, showing first-order neurons travelling from the dorsal root ganglion through the fasciculus gracilis and fasciculus cuneatus to the nucleus gracilis and nucleus cuneatus in the medulla, second-order neurons crossing via the medial lemniscus to the thalamus, and third-order neurons projecting to the postcentral gyrus. On the right, the spinothalamic tract carries pain and temperature sensations from the right side of the body, with first-order neurons in the dorsal root ganglion synapsing in the spinal cord, second-order neurons ascending via the lateral spinothalamic tract to the thalamus, and third-order neurons ending in the postcentral gyrus.
Figure 14.16
Diagram illustrating the vestibulo-ocular reflex showing how head rotation triggers compensating eye movement. The semicircular canals, utricle, and saccule detect rotation, sending signals to the vestibular nuclei in the pons. These connect to the abducens nucleus and oculomotor nucleus, coordinating excitation (shown in magenta) and inhibition (shown in green) of extraocular muscles. During rightward head rotation, excitation occurs in the left lateral rectus and right medial rectus muscles to produce compensating leftward eye movement, while inhibition affects the opposite eye muscles to maintain stable vision.
Figure 14.17
Diagram showing the visual pathways from both eyes to the brain, viewed from below (inferior view). It illustrates how the left and right visual fields overlap to form a binocular field. The optic nerves from each eye meet at the optic chiasm, where fibres from the nasal halves cross to the opposite side, while temporal fibres remain uncrossed. The optic tracts then carry visual information to the lateral geniculate nucleus of the thalamus and onward to the visual cortices of the opposite hemispheres. Additional structures labelled include the pituitary gland and the suprachiasmatic nucleus of the hypothalamus.
Figure 14.18
Diagram of the sensory homunculus, representing the body map on the primary somatosensory cortex. It shows exaggerated body parts corresponding to the amount of cortical area devoted to sensory input from each region. Labels include hip, leg, foot, toes, genitals, trunk, neck, head, shoulder, arm, elbow, forearm, wrist, hand, fingers (little, ring, middle, index, and thumb), eye, nose, face, lips, teeth, gums, jaw, tongue, and pharynx. The hands, lips, and tongue are disproportionately large, reflecting their high sensory sensitivity.
Figure 14.21
Diagram showing the corticospinal (pyramidal) motor pathway from the brain to skeletal muscles. Labels include the precentral gyrus, cerebral peduncle, midbrain, medulla, pyramids, decussation of pyramids, spinal cord, lateral corticospinal tract, anterior corticospinal tract, upper motor neuron, lower motor neuron, and connection to skeletal muscles. A key identifies upper motor neurons in orange and lower motor neurons in green, illustrating how motor commands travel from the cerebral cortex through the brain stem, cross at the medulla, and descend to activate muscle movement.
Figure 15.1
Diagram showing the sympathetic division of the autonomic nervous system, including spinal cord regions, sympathetic chain ganglia, associated nerves, and target organs. The spinal cord extends from the medulla through the thoracic (T1 to T12), lumbar (L1 to L3), sacral (S1 to S5), and coccygeal regions. Labelled structures include the right and left chain ganglia, superior cervical ganglion, greater and lesser splanchnic nerves, celiac ganglion, superior and inferior mesenteric ganglia, and coccygeal ganglia fused together (ganglion impar). Target organs connected by dashed red lines include the eye, lacrimal and salivary glands, heart, lungs, esophagus, stomach, abdominal blood vessels, liver, pancreas, adrenal glands, intestines, rectum, kidneys, bladder, gonads, and external genitalia.
Figure 15.2
Figure illustrating three pathways of sympathetic preganglionic neurons in the autonomic nervous system. Panel A shows a central neuron synapsing at the same spinal level within the sympathetic chain ganglion. Panel B depicts a central neuron synapsing at a superior or inferior ganglion within the chain. Panel C shows a neuron passing through the white ramus without synapsing in the chain ganglion, instead continuing via a splanchnic nerve to a prevertebral ganglion. Labelled structures include the spinal cord, dorsal root ganglion, spinal nerve, white and gray rami communicantes, sympathetic chain ganglion, splanchnic nerve, prevertebral ganglion, and target effectors. A key identifies the axons and cell bodies of central and ganglionic neurons as well as synapses.
Figure 15.3
Diagram illustrating the parasympathetic division of the autonomic nervous system, showing cranial and sacral origins, associated ganglia, and target organs. The spinal cord is labelled with parasympathetic nuclei in the brain stem: Edinger-Westphal nucleus, superior and inferior salivatory nuclei, and dorsal nucleus of the vagus with nucleus ambiguus. Cranial nerves III, VII, IX, and X connect to terminal ganglia—ciliary, pterygopalatine, submandibular, and otic ganglia. Labelled target organs include the eye, lacrimal and salivary glands, mucous membranes, heart, lungs, esophagus, stomach, abdominal blood vessels, liver, pancreas, adrenal glands, intestines, rectum, kidneys, bladder, gonads, and external genitalia. Sympathetic fibres are shown in red and parasympathetic fibres in blue.
Figure 15.4
Diagram showing the structure and function of postganglionic varicosities in autonomic neurotransmission. The left portion depicts a postganglionic axon running along smooth muscle, with multiple swellings labelled as postganglionic varicosities. The magnified view shows a single varicosity containing synaptic vesicles that release neurotransmitters across the gap to bind with neurotransmitter receptors on the sarcolemma (muscle cell membrane). Labelled components include the postganglionic axon, smooth muscle, synaptic vesicles, neurotransmitter, receptors, and sarcolemma.
Figure 15.5
Diagram comparing the autonomic and somatic efferent pathways. The top section illustrates the autonomic efferent pathway, where a central neuron in the spinal cord sends a myelinated autonomic presynaptic axon to a ganglionic neuron, which then connects via an unmyelinated autonomic postsynaptic axon to a smooth muscle target effector. A magnified inset shows a postganglionic varicosity releasing neurotransmitters onto the smooth muscle membrane. The bottom section shows the somatic efferent pathway, where a single myelinated somatic motor neuron extends directly from the spinal cord to a skeletal muscle target effector. The inset depicts a synaptic terminal forming a neuromuscular junction.
Figure 15.7
Diagram comparing long and short reflex pathways in the autonomic nervous system. The upper panel illustrates a long reflex, where a sensory receptor cell sends a signal through a sensory neuron to the spinal cord or brain, synapsing in the central nervous system before continuing through a peripheral ganglion to the target effector. The lower panel shows a short reflex, in which the sensory receptor cell synapses directly within a peripheral ganglion without central nervous system involvement. Both pathways include labelled structures such as the sensory receptor cell, peripheral ganglion, sensory cell synapse, and target effector.
Figure 15.8
Diagram illustrating the neural control of pupil dilation and constriction. At the top, light enters the retina, where ganglion cell bodies send signals via the optic nerve to the brain. The lower half depicts two pathways: In dim light, sympathetic neurons in the cervical vertebra are activated, synapsing in the superior cervical ganglion, and postganglionic neurons release norepinephrine to contract radial iris muscles, dilating the pupils; in bright light, parasympathetic neurons from the Edinger-Westphal nucleus synapse in the ciliary ganglion, and postganglionic neurons release acetylcholine to contract circular iris muscles, constricting the pupils. Colour-coded axons distinguish sympathetic, parasympathetic, and sensory nerves.
Figure 15.9
Diagram illustrating the pupillary light reflex pathway. In step one, light is shone into the right eye. In step two, action potentials from the right eye travel to both right and left pretectal nuclei. In step three, these nuclei stimulate both sides of the Edinger-Westphal nucleus in the midbrain, even though light enters only the right eye. In step four, both Edinger-Westphal nuclei send action potentials through the right and left oculomotor nerves (cranial nerve III) to the ciliary ganglia, causing constriction of both pupils. Key structures labelled include the pretectal nucleus, oculomotor nerves, and ciliary ganglia.
Figure 16.1
This diagram shows the endocrine glands and cells that are located throughout the body. The endocrine system organs include the pineal gland and pituitary gland in the brain. The pituitary is located on the anterior side of the hypothalamus, while the pineal gland is located on the posterior side of the hypothalamus. The thyroid gland is a butterfly-shaped gland that wraps around the trachea within the neck. Four small, disc-shaped parathyroid glands are embedded in the posterior side of the thyroid. The adrenal glands are located on top of the kidneys. The pancreas is located at the centre of the abdomen. In females, the two ovaries are connected to the uterus by two long, curved tubes in the pelvic region. In males, the two testes are located in the scrotum below the penis.
Figure 16.2
This table shows the chemical structure of amine hormones, peptide hormones, protein hormones, and steroid hormones. Amine hormones are amino acids with modified side groups. The example given is norepinephrine, which contains the NH2 group typical of an amino acid, along with a hydroxyl (OH) group. The carboxyl group typical of most amino acids is replaced with a benzene ring, depicted as a hexagon of carbons that are connected by alternating single and double bonds. Peptide hormones are composed of short chains of amino acids. The example given is oxytocin, which has a chain of the following amino acids: Gly, Leu, and Pro. Pro is at the bottom of the chain, which connects to a ring of the following amino acids: Cys, Cys, Tyr, Ile, Glu, and Asp. Protein hormones are composed of long chains of linked amino acids. The example given is human growth hormone, which is composed of a bundle of amino acid strands, some threadlike, some coiled, and some in flat, folded sheets. Finally, steroid hormones are derived from the lipid cholesterol. Testosterone and progesterone are given as examples, which each contain several hexagonal and pentagonal carbon rings linked together.
Figure 16.3
This illustration shows the steps involved with the binding of lipid-soluble hormones. Lipid-soluble hormones, such as steroid hormones, easily diffuse through the cell membrane. The hormone binds to its receptor in the cytosol, forming a receptor-hormone complex. The receptor-hormone complex then enters the nucleus and binds to the target gene on the cell’s DNA. Transcription of the gene creates a messenger RNA that is translated into the desired protein within the cytoplasm. It is these proteins that alter the cell’s activity.
Figure 16.4
This illustration shows the binding of water-soluble hormones. Water-soluble hormones cannot diffuse through the cell membrane. These hormones must bind to a receptor on the outer surface of the cell membrane. The receptor then activates a G protein in the cytoplasm, which travels to and activates adenylyl cyclase. Adenylyl cyclase catalyzes the conversion of ATP to cAMP, the secondary messenger in this pathway. CAMP, in turn, activates protein kinases, which phosphorylate proteins in the cytoplasm. This phosphorylation, shown as a P being added to a polypeptide chain, activates the proteins, allowing them to alter cell activity.
Figure 16.5
This diagram shows a negative feedback loop using the example of glucocorticoid regulation in the blood. Step one in the cycle is when an imbalance occurs. The hypothalamus perceives low blood concentrations of glucocorticoids in the blood. This is illustrated by there being only five glucocorticoids floating in a cross-section of an artery. Step two in the cycle is hormone release, where the hypothalamus releases the corticotropin-releasing hormone (CRH). Step three is labelled “correction.” Here, the CRH release starts a hormone cascade that triggers the adrenal gland to release glucocorticoid into the blood. This allows the blood concentration of glucocorticoid to increase, as illustrated by eight glucocorticoid molecules now being present in the cross-section of the artery. Step four is labelled “negative feedback.” Here, the hypothalamus perceives normal concentrations of glucocorticoids in the blood and stops releasing CRH. This brings blood glucocorticoid levels back to homeostasis.
Figure 16.7
This illustration zooms in on the hypothalamus and the attached pituitary gland. The posterior pituitary is highlighted. Two nuclei in the hypothalamus contain neurosecretory cells that release different hormones. The neurosecretory cells of the paraventricular nucleus release oxytocin (OT), while the neurosecretory cells of the supraoptic nucleus release antidiuretic hormone (ADH). The neurosecretory cells stretch down the infundibulum into the posterior pituitary. The tubelike extensions of the neurosecretory cells within the infundibulum are the hypothalamophypophyseal tracts. These tracts connect with a weblike network of blood vessels in the posterior pituitary called the capillary plexus. From the capillary plexus, the posterior pituitary secretes the OT or ADH into a single vein that exits the pituitary.
Figure 16.8
This illustration zooms in on the hypothalamus and the attached pituitary gland. The anterior pituitary is highlighted. Three neurosecretory cells are secreting hormones into a weblike network of arteries within the infundibulum. The artery net is the primary capillary plexus of the hypophyseal portal system. The superior hypophyseal artery enters the primary capillary plexus from outside of the infundibulum. The hypophyseal portal vein runs down from the primary capillary plexus, through the infundibulum, and connects to the secondary capillary plexus of the hypophyseal portal system. The secondary capillary plexus is located within the anterior pituitary. The hormones released from the neurosecretory cells of the hypothalamus travel through the primary capillary plexus, down the hypophyseal portal vein, and into the secondary capillary plexus. There, the hypothalamus hormones stimulate the anterior pituitary to release its hormones. The anterior pituitary hormones leave the primary capillary plexus from a single vein at the bottom of the anterior lobe.
Figure 16.9
This flowchart illustrates the hormone cascade that stimulates human growth. In step one, the hypothalamus releases growth hormone-releasing hormone (GHRH). GHRH travels into the primary capillary plexus of the anterior pituitary, where it stimulates the anterior pituitary to release growth hormone (GH). The release of GH causes three types of effects. In the glucose-sparing effect, GH stimulates adipose cells to break down stored fat, fueling the growth effects (discussed next). The target cells for the glucose-sparing effects are adipose cells. In the growth effects, GH increases the uptake of amino acids from the blood and enhances cellular proliferation while also reducing apoptosis. The target cells for the growth effects are bone cells, muscle cells, nervous system cells, and immune system cells. In the diabetogenic effect, GH stimulates the liver to break down glycogen into glucose, fueling the growth effects. The liver also releases IGF in response to GH. The IGF further stimulates the growth effects but also negatively feeds back to the hypothalamus. When high IGF-1 levels are perceived by the hypothalamus, it releases growth hormone-inhibiting hormone (GHIH). GHIH inhibits GH release by the anterior pituitary.
Figure 16.10
These two diagrammatic tables show the major pituitary hormones, their releasing hormone from the hypothalamus, their target organs, and their effects. The top part of the diagram shows the posterior pituitary hormones. ADH is produced by the hypothalamus and stored in the posterior pituitary. The targets of ADH are the kidneys, sweat glands, and circulatory system, as this hormone affects water balance. OT is produced by the posterior pituitary and has no releasing hormone. Its target is the female reproductive system, as this hormone triggers uterine contractions during childbirth. The anterior pituitary hormones are listed in the lower diagram. The release of LH by the anterior pituitary is triggered by the release of GnRH from the hypothalamus. The target of LH is the reproductive system, as this hormone stimulates the production of sex hormones by the gonads. The release of FSH by the anterior pituitary is triggered by the release of GnRH from the hypothalamus. The target of FSH is the reproductive system, as this hormone stimulates the production of sperm and eggs. The release of TSH by the anterior pituitary is triggered by the release of TRH from the hypothalamus. The target of TSH is the thyroid gland, as this hormone stimulates the release of thyroid hormone (TH). TH regulates metabolism. The release of PRL by the anterior pituitary is triggered by the release of PRH and inhibited by the release of PIH from the hypothalamus. The target of PRL is the mammary glands, as this hormone promotes milk production. The release of GH by the anterior pituitary is triggered by the release of GHRH and inhibited by the release of GHIH from the hypothalamus. The targets of GH are the liver, bones, and muscles, as it induces its targets to produce insulin-like growth factors (IGF), as this hormone stimulates body growth and a higher metabolic rate. The release of ACTH by the anterior pituitary is triggered by the release of CRH from the hypothalamus. The targets of ACTH are the adrenal glands, as this hormone induces its targets to produce glucocorticoids, which regulate metabolism and the stress response.
Figure 16.11
Part A of this figure is a diagram of the anterior view of the thyroid gland. The thyroid gland is a butterfly-shaped gland wrapping around the trachea. It narrows at its centre, just under the thyroid cartilage of the larynx. This narrow area is called the isthmus of the thyroid. Two large arteries, the common carotid arteries, run parallel to the trachea on the outer border of the thyroid. A small artery enters the superior edge of the thyroid, near the isthmus, and branches throughout the two “wings” of the thyroid. Part B of this figure is a posterior view of the thyroid. The posterior view shows that the thyroid does not completely wrap around the posterior of the trachea. The posterior sides of the thyroid wings can be seen protruding from under the cricoid cartilage of the larynx. The posterior sides of the thyroid “wings” each contain two small, disc-shaped parathyroid glands embedded in the thyroid tissue. Within each wing, one disc is located superior to the other. These are labelled the left and right parathyroid glands. Just under the inferior parathyroid glands are two arteries that bring blood to the thyroid from the left and right subclavian arteries. Part C of this figure is a micrograph of thyroid tissue. The thyroid follicle cells are cuboidal epithelial cells. These cells form a ring around irregular-shaped cavities called follicles. The follicles contain light-coloured colloid. A larger parafollicular cell is embedded between two of the follicular cells near the edge of a follicle.
Figure 16.12
This diagram illustrates a negative feedback loop. It shows the general steps of a negative feedback loop at the centre (imbalance, hormone release, correction, and negative feedback) using the example of the hormone cascade that regulates metabolic rate. The hypothalamus releases TRH in response to low metabolic rate and/or low T3 and T4 concentrations in the blood (imbalance). This triggers TSH release by the pituitary (hormone release). The TSH travels to the thyroid, where it triggers T3 and T4 release by the thyroid cells. T3 and T4 increase basal metabolic rate of the body cells and cause a rise in body temperature (the calorigenic effect). T3 and T4 then feed back to the hypothalamus and inhibit TRH and TSH release. If metabolic rate is high and/or T3 and T4 concentrations are low, then the hypothalamus stops releasing TRH (negative feedback). As a result, the anterior pituitary will not release TSH, and no T3 or T4 will be produced by the thyroid.
Figure 16.13
Illustration showing the thyroid and parathyroid glands with a corresponding histological micrograph. The left panel shows a posterior view of the neck with labelled structures, including the hyoid bone, thyroid cartilage, cricoid cartilage, thyroid gland, and paired left and right parathyroid glands. The right panel presents a micrograph of parathyroid tissue, identifying oxyphil cells, parathyroid (chief) cells, and a blood vessel.
Figure 16.14
This diagram shows the role of parathyroid hormone (PTH) in maintaining blood calcium homeostasis. When blood calcium concentration drops, chief cells of the parathyroid gland release PTH. PTH affects bone, the kidneys, and the intestines. In regard to bone, PTH inhibits osteoblasts and stimulates osteoclasts. This results in compact bone being broken down, as illustrated by an osteoclast burrowing into the surface of a bone. The breakdown releases calcium ions into a nearby blood vessel. The osteoblasts are inactive in this stage. In regard to the kidneys, PTH stimulates kidney tubule cells to recover waste calcium from the urine. PTH also stimulates kidney tubule cells to release calcitriol. This is illustrated with a cross-section of a kidney tubule, showing the cells of the tubule wall. Urine is running to the left of the tubule wall cells, while an artery is to the right. The right edge of the tubule wall cells and the left edge of the artery are separated by a small region of interstitial space. The cells are removing calcium from the urine and pumping it into the interstitial fluid, after which the calcium enters the artery. The cells are also pumping calcitriol into the blood vessel. In regard to the intestine, PTH stimulates the intestines to absorb calcium from digesting food. A cross-section of an intestinal cell is shown, which is cube-shaped but with finger-like projections on the intestinal lumen side (top). Beneath the intestinal cell is an artery. Calcitriol is leaving the artery and entering the intestinal cell, stimulating it to absorb calcium from food in the intestinal lumen. The effects of PTH on bone, the kidneys, and the intestines all cause blood calcium levels to increase. High calcium concentrations in the blood stimulate the parafollicular cells in the thyroid to release calcitonin. Calcitonin reverses the effects of PTH by stimulating osteoblasts and inhibiting osteoclasts in bone tissue. This is illustrated by calcium ions leaving a blood vessel and travelling to osteoblasts on a section of compact bone. The osteoblasts are thickening the compact bone layer, while, in this stage, the osteoclasts are inactive.
Figure 16.15
This diagram shows the left adrenal gland located atop the left kidney. The gland is composed of an outer cortex and an inner medulla, all surrounded by a connective tissue capsule. The cortex can be subdivided into additional zones, all of which produce different types of hormones. The outermost layer is the zona glomerulosa, which releases mineralocorticoids, such as aldosterone, that regulate mineral balance. Underneath this layer is the zona fasciculate, which releases glucocorticoids, such as cortisol, corticosterone, and cortisone, that regulate glucose metabolism. Underneath this layer is the zona reticularis, which releases androgens, such as dehydroepiandrosterone, that stimulate masculinization. Below this layer is the adrenal medulla, which releases stress hormones, such as epinephrine and norepinephrine, that stimulate the sympathetic ANS.
Figure 16.16
This diagram shows the anatomy of the pancreas. The left, larger side of the pancreas is seated within the curve of the duodenum of the small intestine. The smaller, rightmost tip of the pancreas is located near the spleen. The splenic artery is seen travelling to the spleen; however, it has several branches connecting to the pancreas. An interior view of the pancreas shows that the pancreatic duct is a large tube running through the centre of the pancreas. It branches throughout its length into several horseshoe-shaped pockets of acinar cells. These cells secrete digestive enzymes, which travel down the bile duct and into the small intestine. There are also small pancreatic islets scattered throughout the pancreas. The pancreatic islets secrete the pancreatic hormones insulin and glucagon into the splenic artery. An inset micrograph shows that the pancreatic islets are small discs of tissue consisting of a thin, outer ring called the exocrine acinus, a thicker, inner ring of beta cells, and a central circle of alpha cells.
Figure 16.17
This diagram shows the homeostatic regulation of blood glucose levels. Blood glucose concentration is tightly maintained between 70 milligrams per deciliter and 110 milligrams per deciliter. If blood glucose concentration rises above this range (hyperglycemia), insulin is released from the pancreas. Insulin triggers body cells to take up glucose from the blood and utilize it in cellular respiration. Insulin also inhibits glycogenolysis, in that glucose is removed from the blood and stored as glycogen in the liver. Insulin also inhibits gluconeogenesis, in that amino acids and free glycerol are not converted to glucose in the ER. If blood glucose concentration drops below this range, glucagon is released, which stimulates body cells to release glucose into the blood. All these actions cause blood glucose concentration to decrease. When blood glucose concentration is low (hypoglycemia), alpha cells of the pancreas release glucagon. Glucagon inhibits body cells from taking up glucose from the blood and utilizing it in cellular respiration. Glucagon also stimulates glycogenolysis, in that glycogen in the liver is broken down into glucose and released into the blood. Glucagon also stimulates gluconeogenesis, in that amino acids and free glycerol are converted to glucose in the ER and released into the blood. All these actions cause blood glucose concentrations to increase.
Figure 17.1
Illustration comparing hematocrit levels in three test tubes representing different blood conditions. The left tube shows normal blood, with plasma (top yellow layer), buffy coat (thin white layer of white blood cells and platelets), and hematocrit (red blood cell layer) at typical levels—approximately 37 to 47% for females and 42 to 52% for males. The middle tube depicts anemia, with a depressed hematocrit percentage, indicating fewer red blood cells. The right tube shows polycythemia, with an elevated hematocrit percentage, indicating an excess of red blood cells.
Figure 17.2
Diagram showing the process of hematopoiesis, the formation of blood cells from multipotent hematopoietic stem cells. The stem cell divides, with some remaining as stem cells and others differentiating based on chemical signals. The myeloid stem cell line gives rise to megakaryoblasts (then megakaryocytes, then platelets), proerythroblasts (then reticulocytes, then erythrocytes), myeloblasts (then basophils, neutrophils, and eosinophils), and monoblasts (then monocytes). The lymphoid stem cell line forms lymphoblasts, which differentiate into natural killer cells (large granular lymphocytes) and small lymphocytes that become T lymphocytes and B lymphocytes.
Figure 17.5
Diagram showing the life cycle and recycling of red blood cells. In step one, hemopoiesis of erythrocytes begins in hemopoietic bone marrow from stem cells that develop into erythroblasts and reticulocytes. In step two, reticulocytes enter the bloodstream and mature into erythrocytes, which circulate for about 120 days. In step three, aged or damaged erythrocytes are phagocytosed by macrophages in the bone marrow, liver, and spleen. In step four, the globin portion of hemoglobin is broken down into amino acids for reuse in protein synthesis. In step five, the heme portion is degraded into biliverdin, then bilirubin, while iron ions bind to transferrin for transport. In step six, iron is stored as ferritin in the liver or reused in hemopoiesis, while bilirubin contributes to bile formation. The diagram traces heme, iron, and globin recycling pathways, emphasizing the liver’s role in processing and storage.
Figure 17.6
Diagram illustrating leukocyte migration and immune response during infection or injury. In step one, leukocytes—eosinophils, monocytes, and neutrophils—detect chemical attractants released by pathogens and nearby damaged cells in the bloodstream. In step two, leukocytes move toward higher concentrations of these signals (positive chemotaxis) and squeeze between capillary epithelial cells to reach the affected tissue. In step three, in the tissue, monocytes differentiate into macrophages that engulf pathogens, while eosinophils and neutrophils release cytotoxic granules and enzymes to destroy microbes. The process shows leukocyte activation, movement, and phagocytic action at the site of infection.
Figure 17.10
The image illustrates the process of blood clotting, or hemostasis. When a blood vessel is injured, blood components such as erythrocytes, leukocytes, and platelets leak out. Smooth muscle in the vessel wall contracts to reduce blood loss, and platelets adhere to exposed collagen, releasing chemical signals that make them spiked and sticky, forming a platelet plug. During coagulation, fibrinogen is converted to fibrin, creating a mesh that traps blood cells and strengthens the clot. The fibrin synthesis cascade involves intrinsic and extrinsic pathways that converge into a final common pathway. Both pathways activate factor X, which converts prothrombin to thrombin; thrombin then transforms fibrinogen into fibrin, which stabilizes into a cross-linked fibrin clot with the help of factor XIIIa.
Figure 17.11
This image illustrates how maternal sensitization to the Rh factor can lead to hemolytic disease of the newborn. The placenta normally separates maternal and fetal blood, with fetal circulation passing through the umbilical vessels and the embryonic chorion isolating fetal blood from maternal blood pools. During the birth of a first Rh-positive infant, Rh-positive fetal erythrocytes can leak into the Rh-negative mother’s blood when the embryonic chorion ruptures. The maternal immune system recognizes the Rh antigen as foreign, causing B cells to produce anti-Rh antibodies. In a subsequent pregnancy with another Rh-positive fetus, these maternal anti-Rh antibodies, which are small enough to cross the embryonic chorion, enter the fetal circulation and attack the Rh-positive erythrocytes, potentially leading to hemolytic disease in the fetus.
Figure 17.12
This image shows a blood typing test used to determine an individual’s ABO and Rh (D) blood group. Three test wells are labelled “Anti-A,” “Anti-B,” and “Anti-D,” each containing specific antibodies that react with their corresponding antigens on red blood cells. In the sample, agglutination—visible clumping of red blood cells—is observed in the Anti-A and Anti-D wells but not in the Anti-B well. The presence of agglutination indicates that the corresponding antigen is present on the red blood cells. Therefore, this sample is identified as blood type A positive (A plus), meaning the cells have A and Rh (D) antigens but lack the B antigen.
Figure 18.1
This image shows the anatomical position of the heart within the thoracic cavity. The large colour diagram depicts a frontal section through the chest, showing the heart centred between the lungs within the mediastinum, bordered laterally by the right and left lungs and inferiorly by the diaphragm. The superior and inferior venae cavae deliver deoxygenated blood to the right atrium, while the pulmonary trunk and arch of the aorta emerge from the superior aspect of the heart. The right and left auricles and ventricles are visible, and the pericardial cavity surrounds the heart. The smaller sagittal view illustrates the heart’s position relative to the trachea, thymus, aortic arch, esophagus, diaphragm, and thoracic aorta, emphasizing its location behind the sternum and slightly to the left of the midline.
Figure 18.2
This image illustrates the flow of blood through the pulmonary and systemic circuits of the cardiovascular system. The upper diagram shows the internal structure of the heart with labelled chambers, valves, and major vessels. Deoxygenated blood enters the right atrium through the superior and inferior venae cavae, passes through the tricuspid valve into the right ventricle, and is pumped through the pulmonary semilunar valve into the pulmonary trunk, which branches into the right and left pulmonary arteries leading to the lungs. Oxygenated blood returns to the left atrium via the pulmonary veins, flows through the mitral valve into the left ventricle, and exits through the aortic semilunar valve into the aorta for distribution to the body. The lower diagram shows the complete circulation through the human body: Blue vessels represent the pulmonary circuit carrying deoxygenated blood to the lungs, while red vessels represent the systemic circuit delivering oxygenated blood to tissues throughout the upper and lower body before returning to the heart.
Figure 18.4
The image shows anterior and posterior views of the heart with labelled vessels, arteries, and veins. In the anterior view, the labelled parts include the brachiocephalic trunk, left common carotid artery, left subclavian artery, aortic arch, ascending aorta, pulmonary trunk, right and left pulmonary arteries, right and left pulmonary veins, superior vena cava, and inferior vena cava. On the right side of the heart are the right atrium, right auricle, right ventricle, right coronary artery, right marginal artery, small cardiac vein, and anterior cardiac vein. On the left side are the left atrium, auricle of the left atrium, left ventricle, left coronary artery, circumflex artery, great cardiac vein, and anterior interventricular artery. Additional structures shown include the ligamentum arteriosum and the apex of the heart. In the posterior view, the labelled parts include the aorta, superior and inferior venae cavae, right and left pulmonary arteries, and right and left pulmonary veins. On the right side are the right atrium, right ventricle, right coronary artery, posterior interventricular artery, small cardiac vein, and middle cardiac vein. On the left side are the left atrium, auricle of the left atrium, left ventricle, circumflex branch of the left coronary artery, great cardiac vein, posterior vein of the left ventricle, and coronary sinus, with the apex also visible.
Figure 18.7
The image shows an anterior view of the heart, labelled with external and internal anatomical structures. At the top are the aorta, superior vena cava, and pulmonary trunk branching into the right and left pulmonary arteries. The right side includes the right pulmonary veins, right atrium, fossa ovalis, tricuspid valve, right ventricle, chordae tendineae, trabeculae carneae, moderator band, and inferior vena cava. The left side shows the left pulmonary veins, left atrium, mitral (bicuspid) valve, left ventricle, papillary muscle, and interventricular septum. The pulmonary valve and aortic valve are positioned near the centre. The heart wall layers—epicardium, myocardium, and endocardium—are also labelled.
Figure 18.12
The image shows the coronary circulation of the heart in anterior and posterior views. In the anterior view, labelled structures include the aortic arch, ascending aorta, right and left coronary arteries, pulmonary trunk, circumflex artery, anterior interventricular artery, great cardiac vein, right atrium, atrial arteries, anterior cardiac veins, small cardiac vein, and marginal artery. In the posterior view, labelled parts include the coronary sinus, small cardiac vein, circumflex artery, great cardiac vein, marginal artery, posterior interventricular artery, posterior cardiac vein, left ventricle, middle cardiac vein, and right coronary artery.
Figure 18.13
The image shows the structure of cardiac muscle cells and their interconnections. Panel A depicts cardiac muscle fibres with labelled intercalated discs, nuclei, mitochondria, and gap junctions connecting adjacent cells. Panel B presents a micrograph highlighting intercalated discs between striated muscle fibres. Panel C provides a close-up view of the intercalated disc region, showing desmosomes that anchor cells, gap junctions that facilitate electrical connectivity, and A and I bands representing striated sarcomere regions.
Figure 18.14
The image shows the conduction system of the heart in a frontal section. Labelled structures include the sinoatrial (SA) node; the anterior, middle, and posterior internodal pathways; and the atrioventricular (AV) node within the right atrium. The AV bundle (bundle of His) extends into the interventricular septum, dividing into right and left bundle branches that lead to the Purkinje fibres along the ventricular walls. The diagram also labels the arch of the aorta, Bachman’s bundle connecting to the left atrium, the right atrium, the right ventricle, and the left ventricle.
Figure 18.15
The graph shows the pacemaker action potential of cardiac autorhythmic cells, with membrane potential (in millivolts) on the y-axis and time (in seconds) on the x-axis. The trace includes three labelled phases: the slow influx of sodium ions (Na plus) during the prepotential phase, the rapid influx of calcium ions (Ca2 plus) causing depolarization, and the outflux of potassium ions (K plus) leading to repolarization. A dashed line indicates the threshold potential around negative 40 millivolts, and the membrane potential oscillates between approximately negative 60 millivolts and positive 20 millivolts.
Figure 18.16
The image illustrates the cardiac muscle cell action potential and compares it with skeletal muscle. Panel A shows the phases of the cardiac action potential: rapid depolarization caused by sodium (Na plus) influx, a plateau phase from slow calcium (Ca2 plus) influx while Na plus channels close, and repolarization as Ca2 plus channels close and potassium (K plus) channels open. The graph also indicates absolute and relative refractory periods. Panel B compares skeletal and cardiac muscle, showing that skeletal muscle has a short action potential and contraction, whereas cardiac muscle has a longer action potential and contraction due to the extended plateau phase.
Figure 18.17
The image shows a standard electrocardiogram (ECG) trace with labelled waves, intervals, and segments. The top section displays repeating ECG cycles over a one-second interval, while the enlarged lower section highlights individual components: the P wave representing atrial depolarization, the QRS complex representing ventricular depolarization, and the T wave representing ventricular repolarization. Labelled intervals include the PR interval between the P and Q waves and the QT interval from Q to T, while the PR and ST segments indicate periods between depolarization and repolarization events. The y-axis shows voltage in millivolts, and the x-axis represents time.
Figure 18.18
The diagram illustrates the cardiac conduction cycle through six stages, each linked to an electrocardiogram (ECG) waveform segment. Stage one shows the resting heart before depolarization. In stage two, the sinoatrial (SA) node fires, initiating atrial depolarization, represented by the P wave. Stage three shows full atrial depolarization as impulses reach the atrioventricular (AV) node. In stage four, depolarization spreads through the AV bundle and bundle branches, producing the QRS complex as ventricles depolarize. Stage five depicts complete ventricular depolarization, and stage six shows ventricular repolarization associated with the T wave, completing one heartbeat before returning to rest. Red arrows indicate the sequence of electrical activation through the heart.
Figure 18.19
The diagram shows the cardiac cycle, linking mechanical heart activity with electrical signals on an ECG. The cycle begins with ventricular filling during late ventricular diastole, followed by atrial contraction marking atrial systole, associated with the P wave. Next is isovolumic contraction at the start of ventricular systole, leading to ventricular contraction and ejection phases corresponding to the QRS complex as blood is pumped out of the ventricles. The cycle concludes with isovolumic relaxation during early ventricular diastole, associated with the T wave as the ventricles repolarize. Purple arrows indicate the sequence of events through atrial and ventricular systole and diastole.
Figure 18.20
The diagram illustrates one cardiac cycle, showing the relationship between the electrocardiogram (ECG) waveform and the mechanical phases of atrial and ventricular activity. The P wave corresponds to atrial systole, during which the atria contract. The QRS complex represents ventricular systole, or contraction, as the ventricles depolarize and pump blood. The T wave marks ventricular diastole, or relaxation, as the ventricles repolarize. Below the ECG, colour-coded bars indicate alternating periods of atrial systole and diastole (orange) and ventricular systole and diastole (green), demonstrating how the chambers contract and relax in a coordinated sequence to complete one full cardiac cycle.
Figure 18.21
The diagram shows the relationship between pressure changes in the atria, ventricles, and aorta during one cardiac cycle, along with corresponding heart sounds. Atrial pressure (orange) remains low, ventricular pressure (green) rises sharply during systole, and aortic pressure (red) increases as the semilunar valves open. The first heart sound, “lub,” occurs when the atrioventricular (AV) valves close at the start of ventricular systole. The second sound, “dub,” occurs when the semilunar valves close, marking the onset of ventricular diastole. The brief third sound is linked to ventricular filling. Valve opening and closing events are indicated along the curves, showing how pressure dynamics coordinate with the heart’s rhythmic sounds.
Figure 18.23
The diagram summarizes the factors that influence cardiac output (CO), which equals heart rate (HR) multiplied by stroke volume (SV). Factors affecting heart rate include autonomic innervation, hormones, fitness levels, and age. Factors affecting stroke volume include heart size, fitness levels, gender, contractility, duration of contraction, preload (end-diastolic volume, EDV), and afterload (resistance). Stroke volume is calculated as the difference between EDV and end-systolic volume (ESV). Together, HR and SV determine overall cardiac output, representing the volume of blood pumped by the heart per minute.
Figure 18.25
The diagram shows how autonomic stimulation affects cardiac pacemaker activity through changes in membrane potential over time. In the normal (resting) state, spontaneous depolarization, or prepotential, triggers regular action potentials. During parasympathetic stimulation, hyperpolarization and slower depolarization occur, decreasing heart rate. Under sympathetic stimulation, reduced repolarization and faster depolarization lead to more frequent action potentials, increasing heart rate. The graphs illustrate how autonomic control adjusts heart rhythm by modulating the rate of depolarization in pacemaker cells.
Figure 18.26
The diagram illustrates the interconnected factors that regulate cardiac output (CO), defined as heart rate (HR) multiplied by stroke volume (SV). Heart rate is influenced by autonomic innervation, hormones, and the atrial reflex. Stroke volume is determined by three main factors—preload, contractility, and afterload. Preload is affected by venous return and filling time, while contractility depends on autonomic innervation and hormones. Afterload is influenced by vasodilation or vasoconstriction. Preload contributes to end-diastolic volume (EDV), and both contractility and afterload affect end-systolic volume (ESV). Stroke volume is calculated as EDV minus ESV, and together with heart rate, these mechanisms determine total cardiac output.
Figure 19.1
The diagram illustrates the pathways of pulmonary and systemic circulation. In pulmonary circulation, deoxygenated blood flows from the heart through the pulmonary artery to the lungs, where gas exchange occurs, and oxygenated blood returns via the pulmonary veins. In systemic circulation, oxygenated blood is pumped from the heart through the aorta to the upper body, liver, stomach, intestines, kidneys, and lower body. Blood passes through arteries, capillaries, and veins—shown in red for oxygenated, blue for deoxygenated, and purple for gas exchange vessels—before returning via the vena cava. Key labelled structures include the pulmonary artery and vein, aorta, vena cava, hepatic artery and vein, hepatic portal vein, renal artery and vein, and organs such as the lungs, liver, kidneys, and digestive tract.
Figure 19.2
The image compares the structure of arteries and veins in both diagrams and a histological view. The artery wall shows three layers: the tunica intima, tunica media, and tunica externa. It includes an endothelium, elastic fibres, internal and external elastic membranes, smooth muscle, vasa vasorum, and nervi vasorum, indicating a thick, elastic, and muscular structure. The vein wall also consists of the same three layers but has a thinner tunica media, less smooth muscle and elastic tissue, and a larger lumen. The vasa vasorum and endothelium are visible, but the elastic membranes are less distinct. The histological section shows the artery with a thick, circular wall and narrow lumen, while the vein appears thinner-walled and irregular, demonstrating structural differences suited to their functions in blood transport.
Figure 19.3
The diagram compares the wall structures of an elastic artery, muscular artery, and arteriole. All three have three layers: tunica intima, tunica media, and tunica externa. The elastic artery has a thick tunica media rich in elastic fibres that allow it to stretch and recoil with blood pressure changes. The muscular artery has a smaller proportion of elastic fibres and a thicker tunica media composed mainly of smooth muscle for regulating blood flow through vasoconstriction and vasodilation. The arteriole has the thinnest wall, with only a few layers of smooth muscle in the tunica media and a thin tunica externa, allowing fine control of blood flow into capillary networks.
Figure 19.7
The image is a line graph showing changes in blood pressure throughout the circulatory system. The y-axis represents pressure in millimetres of mercury from 0 to 120, and the x-axis shows vessel types from left to right: aorta, elastic arteries, muscular arteries, arterioles, capillaries, venules, medium and large veins, and venae cavae. The graph includes three labelled curves: systolic pressure (upper line), mean arterial pressure (middle line), and diastolic pressure (lower line). Pulse pressure is indicated on the left side, and the oscillations of the systolic and diastolic lines gradually decrease as blood moves from the arteries through the veins.
Figure 19.9
The image is a graph showing how blood pressure is measured using Korotkoff sounds. The y-axis represents pressure in millimetres of mercury from 60 to 140, and the x-axis represents time. A red line shows oscillating blood pressure waves, while a gray line indicates cuff pressure decreasing over time. Two dashed vertical lines mark key points: The first sound heard corresponds to systolic blood pressure, and the last sound heard corresponds to diastolic blood pressure. Below the graph, a series of black spikes labelled “Korotkoff sounds in stethoscope” align with the period between the systolic and diastolic pressure markers.
Figure 19.10
The image contains four line graphs comparing properties of blood vessels across different types. Graph A shows vessel diameter, which decreases from elastic arteries to capillaries and then increases through veins to the venae cavae. Graph B shows total cross-sectional area, which remains low through arteries, peaks sharply at capillaries, and decreases again toward the veins. Graph C shows average blood pressure, starting high in elastic arteries and steadily declining through veins. Graph D shows velocity of blood flow, which is high in arteries, slows significantly at capillaries, and increases again in veins.
Figure 19.12
The image illustrates capillary fluid exchange along three regions of a capillary: the arterial end, mid-capillary, and venous end. On the left, labelled “Filtration,” a large red upward arrow shows fluid exiting the capillary. The arterial end has a net filtration pressure of positive 10 millimetres of mercury because capillary hydrostatic pressure (35 millimetres of mercury) exceeds blood colloidal osmotic pressure (25 millimetres of mercury). In the centre, labelled “No net movement,” a purple upward arrow indicates equilibrium, with net filtration pressure at 0 millimetres of mercury as both pressures equal 25 millimetres of mercury. On the right, labelled “Reabsorption,” a large blue downward arrow shows fluid reentering the capillary. The venous end has a net filtration pressure of negative 7 millimetres of mercury because capillary hydrostatic pressure (18 millimetres of mercury) is less than blood colloidal osmotic pressure (25 millimetres of mercury).
Figure 19.13
The image is a flowchart showing the mechanisms regulating blood flow and pressure through autoregulation, neural mechanisms, and endocrine control. The top section, labelled “Autoregulation,” begins with normal resting conditions, where changes to blood flow detected by local receptors lead to either vasodilation or vasoconstriction. Vasodilators, such as decreased O2, increased CO2, metabolic acids, nitric oxide, potassium, hydrogen ions, inflammation, and increased body temperature, relax precapillary sphincters to increase blood flow, while vasoconstrictors, like prostaglandins and products from activated platelets, leukocytes, and endothelins, constrict sphincters to decrease flow. Both lead to restored homeostasis. The middle section, “Neural and endocrine mechanisms,” divides into neural and endocrine pathways. The neural mechanism influences blood pressure and blood chemistry through cardiac and vasomotor centres. Sympathetic stimulation increases cardiac output and blood flow, parasympathetic stimulation decreases them, and specific neurotransmitters cause vasoconstriction or vasodilation, leading to homeostasis restoration. The endocrine control section shows renal, adrenal, brain, and heart inputs producing hormones such as erythropoietin, renin, angiotensin, aldosterone, catecholamines, antidiuretic hormone, and atrial natriuretic hormone, which regulate blood volume, pressure, and vessel tone via vasoconstriction or vasodilation.
Figure 19.14
The image is a flowchart showing how baroreceptor reflexes regulate blood pressure to maintain homeostasis. The top half illustrates the response to increased blood pressure: Elevated blood pressure increases baroreceptor firing, which stimulates cardiac inhibitor centres while inhibiting cardiac accelerator and vasomotor centres. This decreases cardiac output (heart rate and stroke volume) and causes vasodilation, resulting in a drop in blood pressure and the restoration of homeostasis. The bottom half shows the response to decreased blood pressure: Reduced blood pressure lowers baroreceptor firing, decreasing activity in cardiac inhibitor centres and increasing activity in cardiac accelerator and vasomotor centres. This raises cardiac output and causes vasoconstriction, which increases blood pressure and restores homeostasis.
Figure 19.15
The flowchart depicts the short-term and long-term responses to decreased blood pressure and/or volume. In the short-term pathway, decreased blood pressure and volume trigger sympathetic activation, causing the adrenal glands to release epinephrine and norepinephrine, which increase cardiac output and peripheral vasoconstriction. These changes raise blood pressure, restoring homeostasis. In the long-term pathway, decreased blood pressure and volume cause the kidneys to produce renin and erythropoietin. Renin activates angiotensin II, leading to the release of antidiuretic hormone and secretion of aldosterone, as well as stimulation of thirst. These processes increase blood volume, while erythropoietin increases red blood cell formation, further increasing blood volume. The resulting rise in blood volume contributes to the restoration of homeostasis.
Figure 19.16
The flowchart depicts mechanisms that respond to decreased blood pressure and volume. The response divides into endocrine and neural mechanisms. The endocrine mechanism releases antidiuretic hormone (ADH), angiotensin II, aldosterone, and erythropoietin (EPO), which increase blood volume, leading to restoration of homeostasis. The neural mechanism stimulates baroreceptors and chemoreceptors, which activate cardiovascular centres and trigger general sympathetic activation, causing the release of norepinephrine and epinephrine. These actions increase cardiac output, cause peripheral vasoconstriction, raise blood pressure, and reduce venous reserve, ultimately restoring homeostasis.
Figure 19.17
The diagram shows the pulmonary circulation within the thoracic cavity, including the heart and lungs. The superior and inferior vena cavae carry deoxygenated blood into the right atrium of the heart, which then passes through the right ventricle and into the pulmonary trunk. The trunk branches into right and left pulmonary arteries that extend to the right and left lungs. Within each lung, the arteries branch into smaller vessels leading to the pulmonary capillaries, shown in a magnified inset where red and blue vessels intertwine. Oxygenated blood returns from the lungs through the right and left pulmonary veins to the left atrium of the heart. The ascending aorta and aortic arch emerge from the left ventricle and continue as the descending aorta.
Figure 19.18
The image shows an anterior view of a human body, highlighting the major systemic arteries in red, with labels identifying key vessels throughout the body. In the head and neck, the vertebral, right subclavian, right common carotid, left common carotid, and left subclavian arteries are labelled. The thoracic region includes the brachiocephalic trunk, aortic arch, ascending aorta, pulmonary trunk, axillary artery, and descending aorta. The abdominal region features the celiac trunk, diaphragm, renal arteries, superior mesenteric, gonadal, and inferior mesenteric arteries. The pelvis and lower limbs show the common iliac, internal iliac, and external iliac arteries branching into the femoral and deep femoral arteries. Farther down the leg, the descending genicular, popliteal, posterior tibial, anterior tibial, fibular, dorsalis pedis, and plantar arch arteries are identified. In the upper limbs, the brachial, radial, ulnar, and palmar arch arteries are labelled, showing the arterial network extending into the hands.
Figure 19.19
The image shows the major arteries branching from the aorta. The ascending aorta extends upward from the heart and gives rise to the right and left coronary arteries. The vessel curves into the aortic arch, from which the brachiocephalic artery, left common carotid artery, and left subclavian artery emerge. The brachiocephalic artery branches into the right subclavian and right common carotid arteries. Below the arch, the aorta continues as the descending aorta, which becomes the thoracic aorta and then the abdominal aorta.
Figure 19.20
The illustration shows arteries of the head and neck in a right lateral view, with vessels highlighted in red. The common carotid artery ascends along the neck and divides into the internal and external carotid arteries. The internal carotid extends upward toward the skull, while the external carotid branches into the occipital, lingual, facial, maxillary, and superficial temporal arteries. The carotid sinus is located at the base of the internal carotid. The vertebral artery runs upward through the cervical vertebrae, contributing to the blood supply of the brain.
Figure 19.21
The diagram shows the thoracic and abdominal aorta with major arterial branches. From the aortic arch, the thoracic aorta descends through the chest, giving rise to parietal branches, including the intercostal and superior phrenic arteries, and visceral branches, including the bronchial, esophageal, mediastinal, and pericardial arteries. The thoracic aorta passes through the diaphragm via the aortic hiatus to become the abdominal aorta. Below the diaphragm, branches include the inferior phrenic, adrenal, renal, gonadal, lumbar, and median sacral arteries. The celiac trunk divides into the left gastric, splenic, and common hepatic arteries, with the superior and inferior mesenteric arteries branching farther down. The abdominal aorta terminates by dividing into the common iliac arteries, which branch into internal and external iliac arteries.
Figure 19.22
The diagram lists unpaired and paired arterial branches of the thoracic and abdominal aorta along with their target structures. From the thoracic aorta, unpaired branches include the bronchial arteries supplying air passages and lung tissue, pericardial arteries supplying the pericardium, esophageal arteries supplying the esophagus, and mediastinal arteries supplying mediastinal structures. Paired thoracic branches include the intercostal arteries supplying vertebrae, spinal cord, back muscles, body wall, and skin, and the superior phrenic arteries supplying similar regions and the diaphragm. From the abdominal aorta, unpaired branches include the left gastric, splenic, and common hepatic arteries forming the celiac trunk, which supplies the stomach, spleen, pancreas, liver, gallbladder, duodenum, and part of the esophagus. The superior mesenteric artery supplies the pancreas, small intestine, appendix, and most of the large intestine, while the inferior mesenteric artery supplies the last third of the large intestine. Paired abdominal branches include the inferior phrenic arteries to the diaphragm and lower esophagus, adrenal arteries to the adrenal glands, renal arteries to the kidneys, gonadal arteries to the testes or ovaries, and lumbar arteries to the vertebrae, spinal cord, abdominal wall, and lumbar region. The diagram ends with the median sacral artery and the paired common iliac arteries branching from the lower abdominal aorta.
Figure 19.23
The diagram depicts arterial branches of the abdominal aorta, focusing on the iliac arteries and their major subdivisions. The abdominal aorta divides into the right and left common iliac arteries, with the left side following the same pattern as the right. The median sacral artery extends downward from the aortic bifurcation. The right common iliac supplies the pelvis and right lower limb and divides into the right external and right internal iliac arteries. The right external iliac continues to the right lower limb. The right internal iliac supplies pelvic muscles, skin, pelvic viscera, perineum, gluteal region, and medial thigh and branches into the superior gluteal, obturator, internal pudendal, and lateral sacral arteries. The superior gluteal supplies hip muscles and the hip joint; the obturator supplies the ilium, hip and thigh muscles, hip joint, and femoral head; the internal pudendal supplies the rectum, anus, perineal muscles, external genitalia, and lateral rotators of the hip; and the lateral sacral supplies the skin and muscles of the sacrum.
Figure 19.24
The image shows the arterial network of the right arm. The right subclavian artery continues into the axillary artery, which gives rise to the humeral circumflex and deep brachial arteries. The brachial artery extends along the upper arm, branching into the ulnar collateral artery near the elbow. In the forearm, the radial and ulnar arteries run parallel, joined by the anterior crural interosseous artery between them. Near the wrist, the radial and ulnar arteries contribute to the deep and superficial palmar arches, which give rise to the digital arteries that supply the fingers.
Figure 19.25
The diagram illustrates arterial branches from the aortic arch supplying the upper body and arms. The aortic arch arises from the left ventricle and gives rise to the brachiocephalic trunk, left common carotid, and left subclavian arteries. The brachiocephalic trunk divides into the right common carotid and right subclavian arteries. Each subclavian gives rise to the vertebral artery, thyrocervical trunk, and internal thoracic artery. The vertebral arteries ascend to supply the spinal cord and cervical vertebrae, joining within the cranium to form the basilar artery. The thyrocervical trunks supply the muscles, tissues, and skin of the neck and the thyroid gland, shoulders, and upper back. The internal thoracic arteries supply the skin and muscles of the chest and the abdomen, mammary glands, and pericardium. Each subclavian continues as the axillary artery, which supplies the pectoral and axilla muscles, then becomes the brachial artery, supplying the arm and elbow. The brachial artery divides into the radial and ulnar arteries, which run along the respective sides of the forearm and join in the hand to form the digital arteries.
Figure 19.26
The image shows anterior and posterior views of the arteries of the leg. In the anterior view, the common, external, and internal iliac arteries are visible at the upper pelvis, with branches including the lateral sacral, internal pudendal, and obturator arteries. The femoral artery extends down the thigh, giving rise to the deep femoral and lateral femoral circumflex arteries, then continues as the genicular and popliteal arteries near the knee. Below the knee, the anterior tibial, posterior tibial, and fibular arteries supply the lower leg, ending in the dorsalis pedis and dorsal arch at the foot. In the posterior view, the same major vessels are shown from behind, with the peroneal artery accompanying the tibial arteries down the leg and branching into the lateral and medial plantar arteries, which connect to the plantar arch in the foot.
Figure 19.27
The diagram outlines the arterial branches of the lower limb originating from the external iliac artery. The external iliac continues as the femoral artery, which supplies the thigh and gives rise to the descending genicular artery for the knee joint and leg skin. The deep femoral artery branches from the femoral and supplies the hip joint, femoral head, and deep thigh muscles. From the deep femoral artery, the median femoral circumflex artery supplies the adductor and obturator muscles and the hip joint, while the lateral femoral circumflex artery supplies the quadriceps muscles. The femoral artery continues as the popliteal artery, which supplies the leg and foot and divides into the anterior and posterior tibial arteries. The anterior tibial leads to the dorsalis pedis, dorsal arch, and plantar arch, which connect to the dorsal metatarsal and dorsal digital arteries supplying the distal foot and toes. The posterior tibial gives rise to the fibular and peroneal arteries, which also contribute to the lower leg and foot circulation.
Figure 19.28
The image shows an anterior view of the human body, highlighting the systemic veins in blue. In the head and neck, the external and internal jugular veins drain into the subclavian and brachiocephalic veins, which merge into the superior vena cava. The thoracic region includes the intercostal and hepatic veins connecting to the inferior vena cava. The upper limbs show the cephalic, basilic, brachial, axillary, and subclavian veins, with additional branches including the radial, ulnar, median antebrachial, and median cubital veins, as well as the palmar venous arches and digital veins in the hands. In the abdominal region, the renal, gonadal, and lumbar veins drain into the inferior vena cava. The pelvis and lower limbs feature the right and left common, external, and internal iliac veins, which connect to the femoral and deep femoral veins. The great saphenous, small saphenous, popliteal, fibular, anterior tibial, and posterior tibial veins continue down the legs, leading to the plantar and dorsal venous arches of the feet.
Figure 19.29
The image shows the major veins of the thoracic and abdominal regions in blue. The superior vena cava receives blood from the vertebral, internal jugular, external jugular, subclavian, brachiocephalic, axillary, and cephalic veins. Within the thorax, the mediastinal, esophageal, internal thoracic, intercostal, azygos, and hemiazygos veins drain into the superior vena cava. The inferior vena cava ascends through the abdomen, collecting blood from the hepatic, phrenic, adrenal, renal, gonadal, lumbar, and common iliac veins. The common iliac veins divide into internal and external iliac branches, which drain blood from the pelvis and lower limbs. The kidneys and adrenal glands are positioned on either side of the inferior vena cava, with their respective veins connecting directly to it.
Figure 19.30
The illustration shows the major veins of the head and neck in a right lateral view, highlighting venous sinuses and drainage pathways in blue. The superior and inferior sagittal sinuses, straight sinus, and occipital sinus converge posteriorly, connecting to the right transverse and sigmoid sinuses. The petrosal sinus links the cavernous sinus, located near the base of the skull, with the internal jugular vein. Additional labelled veins include the temporal, maxillary, facial, external jugular, and vertebral veins. The internal jugular vein descends alongside the neck to join the right subclavian vein, forming the superior vena cava via the brachiocephalic vein.
Figure 19.31
The image shows the superficial and deep veins of the right arm, indicated by different shades of blue. The superficial veins, shown in light blue, include the cephalic, basilic, median cubital, and median antebrachial veins, along with the palmar venous arches and digital veins in the hand. The deep veins, shown in dark blue, include the radial, ulnar, brachial, subscapular, axillary, and subclavian veins. The cephalic vein runs along the lateral side of the arm, while the basilic vein runs medially. The median cubital vein connects the cephalic and basilic veins near the elbow. Both superficial and deep veins drain blood from the hand and forearm into larger vessels that return to the subclavian vein near the shoulder.
Figure 19.32
The diagram illustrates major veins of the upper body and their drainage pathways leading to the superior vena cava. The right and left brachiocephalic veins converge into the superior vena cava, which empties into the right atrium. Each brachiocephalic vein receives blood from the vertebral, internal jugular, external jugular, subclavian, and internal thoracic veins. The vertebral veins collect blood from the cranium, spinal cord, and vertebrae, while the internal and external jugular veins drain the cranium, face, neck, scalp, and salivary glands. The subclavian veins collect blood from the upper limbs, with the left side detailed further: The axillary vein receives the cephalic and basilic veins, draining the lateral and medial surfaces of the arm, respectively, through the median cubital and median antebrachial veins. The internal thoracic veins collect blood from the anterior thoracic wall. Additional veins include the azygos and hemiazygos veins, which drain the intercostal and esophageal veins from the vertebrae, body wall, and esophagus, joining the superior vena cava through mediastinal connections.
Figure 19.33
The diagram shows the major veins draining into the inferior vena cava and their associated regions. The inferior vena cava carries blood to the right atrium and receives contributions from the hepatic veins draining the liver, the phrenic veins draining the diaphragm, the adrenal veins draining the adrenal glands, the renal veins draining the kidneys, the gonadal veins draining the testes or ovaries, and the lumbar veins draining the spinal cord and body wall. Below these, the right and left common iliac veins merge to form the inferior vena cava. Each common iliac divides into external and internal iliac veins. The external iliac veins drain the lower limbs, while the internal iliac veins drain pelvic muscles, skin, pelvic viscera, the perineum, and the gluteal region. The internal iliac veins give rise to the superior gluteal, internal pudendal, obturator, and lateral sacral veins, which return blood from their respective areas.
Figure 19.34
The image shows anterior and posterior views of the veins of the leg. In the anterior view, major veins include the common, external, and internal iliac veins, along with the gluteal, lateral sacral, internal pudendal, obturator, femoral, deep femoral, and femoral circumflex veins. The femoral vein continues downward to the popliteal vein behind the knee, which receives the great and small saphenous veins. Below the knee, the anterior tibial, posterior tibial, and fibular veins drain the lower leg. The foot contains the dorsal venous arch and digital veins. In the posterior view, the same veins are visible from behind, with the addition of the lateral and medial plantar veins and the plantar venous arch in the foot, which merge into the posterior tibial vein.
Figure 19.35
The diagram outlines the major veins of the lower limb and their connections. The external iliac vein continues as the femoral vein, which receives blood from the deep femoral vein draining the thigh and the great saphenous vein collecting blood from the superficial veins of the lower limb. The small saphenous vein joins the popliteal vein, which collects blood from the superficial veins of the leg and foot. The popliteal vein divides into the anterior tibial, posterior tibial, and fibular veins. These veins drain into the lateral and medial plantar veins as well as the dorsal and plantar arches of the foot. The metatarsal and digital veins collect blood from the distal foot and toes, feeding into these arches and then upward through the tibial and fibular veins.
Figure 19.36
The image shows the hepatic portal system and its associated veins draining the digestive organs. The hepatic portal vein, shown in black, receives blood from the superior mesenteric, splenic, and inferior mesenteric veins. The superior mesenteric vein, coloured green, drains the small intestine and portions of the large intestine through the intestinal, ileocolic, right colic, middle colic, pancreaticoduodenal, and gastro-omental veins. The splenic vein, shown in orange, collects blood from the spleen and receives the pancreatic and gastroepiploic veins. The inferior mesenteric vein, shown in purple, drains the distal portion of the large intestine through the superior rectal, sigmoid, and left colic veins. The hepatic portal vein also connects with the right gastric and cystic veins from the stomach and gallbladder. Blood from these vessels ultimately flows to the liver for processing before entering systemic circulation.
Figure 19.37
The image shows fetal circulation with labelled vessels and shunts. The umbilical vein carries oxygenated blood from the placenta to the fetus, where it passes through the ductus venosus into the inferior vena cava. Blood enters the right atrium and moves through the foramen ovale into the left atrium, then into the aorta for systemic circulation. Some blood flows from the pulmonary trunk through the ductus arteriosus into the aorta. Deoxygenated blood returns to the placenta through the paired umbilical arteries branching from the internal iliac arteries. The placenta, bladder, aorta, and major fetal vessels are shown in context.
Figure 20.1
The image shows the human lymphatic system with major organs, vessels, and structures highlighted. Green lymphatic vessels extend throughout the body, connecting lymph nodes, the spleen, thymus, and tonsils. The adenoid and tonsil are located in the head, the thymus in the upper chest, and the spleen in the upper left abdomen. The right lymphatic duct enters a large vein near the shoulder, returning lymph to circulation. The bone marrow in the leg is shown as a source of immune cells. Insets display the thymus as a lobed gland, a lymph node with labelled masses of lymphocytes and macrophages, and a close-up of tissue showing lymphatic capillaries, blood capillaries, interstitial fluid, and tissue cells.
Figure 20.2
The image shows lymph capillaries within tissue spaces and their relationship to surrounding structures. On the left, red arterioles, blue venules, and green lymphatic vessels are shown among tissue cells. Lymph capillaries collect tissue fluid that enters through overlapping endothelial flaps. The inset magnifies a section of lymphatic capillary, showing collagen fibres anchoring it to tissue, interstitial fluid between cells, lymph vessel endothelial cells forming one-way valves, and backflow prevention valves ensuring unidirectional lymph flow. Arrows indicate the movement of tissue fluid into the lymph capillary and through the lymphatic vessel.
Figure 20.3
The image shows the regions of the body drained by the right lymphatic duct and the thoracic duct. The right lymphatic duct, shown draining the upper right portion of the body shaded in purple, empties into the junction of the right subclavian and right internal jugular veins. The thoracic duct, shown in green, drains the remainder of the body and empties into the junction of the left subclavian and left internal jugular veins. The thoracic duct originates from the cisterna chyli, located near the lower abdomen. Insets show close-up views of each duct entering the subclavian veins on the right and left sides.
Figure 20.4
The diagram shows the development of blood cells from a multipotent hematopoietic stem cell, also called a hemocytoblast. After division, some cells remain stem cells, while others differentiate based on chemical signals into two main lineages: myeloid and lymphoid stem cells. The myeloid stem cell gives rise to megakaryoblasts, proerythroblasts, myeloblasts, and monoblasts. Megakaryoblasts form megakaryocytes, which produce platelets. Proerythroblasts become reticulocytes and then mature erythrocytes. Myeloblasts differentiate into basophils, neutrophils, and eosinophils, while monoblasts form monocytes that mature into macrophages. The lymphoid stem cell forms lymphoblasts, which give rise to natural killer cells and small lymphocytes. Small lymphocytes differentiate into T lymphocytes and B lymphocytes, with B lymphocytes further developing into plasma cells.
Figure 20.6
The image shows the lymphatic and immune structures of the upper body, along with thymus anatomy and microscopic details. The human figure depicts lymphatic vessels in green connecting the adenoids, tonsils, thymus, lymph nodes, spleen, and right lymphatic duct entering a large vein near the heart. The upper inset shows a histological section of the thymus with labelled cortex, medulla, trabeculae, and fibrous capsule. The lower inset illustrates thymic microanatomy, showing cortical epithelial cells, thymocytes, dendritic cells, macrophages, medullary epithelial cells, trabeculae, and blood vessels organized within the cortex and medulla beneath a fibrous capsule.
Figure 20.7
The image shows the structure of a lymph node through a histological section and a labelled diagram. The left side displays a microscope view with purple-stained tissue, identifying the connective tissue capsule, cortex, subcapsular sinus, and germinal centres. The accompanying diagram on the right depicts a cutaway view of a lymph node, showing afferent lymphatic vessels entering the node, the subcapsular sinus beneath the capsule, trabeculae extending inward, germinal centres within the cortex, and efferent lymphatic vessels exiting the node. The connective tissue capsule surrounds the entire node, maintaining its structure.
Figure 20.8
The image shows the structure and histology of the spleen. In part A, a human figure indicates the spleen’s location near the diaphragm, with a labelled cross-section showing the hilum, splenic artery, and splenic vein. A detailed view of splenic tissue illustrates red pulp, white pulp, trabeculae, arterioles, and venules. In part B, a magnified histological section shows the spleen’s internal organization, including trabeculae, a marginal zone, central artery or arteriole, germinal centre, arterial capillaries, venous sinus, and surrounding red pulp.
Figure 20.9
The image shows the anatomy and histology of the tonsils. In part A, diagrams illustrate the locations of the pharyngeal, palatine, and lingual tonsils within the upper airway. The pharyngeal tonsil lies in the nasopharynx near the sphenoidal sinus and bone, while the palatine tonsil is located between the soft palate and tongue, and the lingual tonsil sits at the base of the tongue near the epiglottis. A photograph shows the palatine tonsils visible at the back of the throat, swollen due to infection. In part B, a histological section of the palatine tonsil shows crypts lined by stratified squamous epithelium and multiple germinal centres within lymphoid tissue.
Figure 20.11
The image illustrates innate and adaptive immunity. The upper section shows pathogens entering through the mouth and nose near the palatine tonsil. Arrows indicate the first line of innate defences, including surface barriers such as skin, hair, and mucus, and internal defences involving mast cells and basophils releasing histamine, natural killer cells, the complement system, and phagocytes such as monocytes, neutrophils, and macrophages. The lower section represents adaptive immunity in the germinal centre of a palatine tonsil, showing T lymphocytes, antigen-presenting cells, and B lymphocytes forming T effector cells, T memory cells, B effector cells, and B memory cells, with antibodies released into the surrounding area.
Figure 20.14
The image illustrates antigen processing and presentation by a dendritic cell. It begins with the dendritic cell engulfing a pathogen into a vesicle, where lysosomes release enzymes to digest it and extract antigens. These antigens bind to MHC class II proteins within the vesicle, and the MHC-antigen complexes are transported to the cell surface. The dendritic cell then displays the antigens on its membrane, allowing interaction with T cells whose receptors recognize and bind to the presented antigens, initiating an adaptive immune response.
Figure 20.15
The image illustrates the activation of cytotoxic T cells. A dendritic cell presents an antigen from a pathogen on its MHC class I protein to a naive cytotoxic T (TC) cell. The T cell receptor and CD8 molecule on the TC cell bind to the antigen-MHC complex, activating the TC cell. The activated TC cells then multiply, producing two groups: effector TC cells that destroy infected cells in the body and memory TC cells that remain to respond rapidly if the same antigen is encountered again.
Figure 20.17
The image compares the primary and secondary immune responses. On the left, the primary response begins when an antigen binds to a specific B cell receptor, activating the B cell and causing it to form clones. These clones differentiate into plasma cells, which secrete antibodies, and memory B cells, which remain in the body. On the right, the secondary response shows that when the same antigen is encountered again, memory B cells rapidly produce clones that generate plasma cells and antibodies in greater quantity and more quickly than in the primary response.
Figure 21.3
The image shows a sagittal section of the upper respiratory tract and surrounding structures. It labels key regions, including the nasal cavity (with nasal conchae, meatuses, and vestibule), paranasal sinuses (frontal and sphenoidal), and olfactory epithelium. The pharynx is divided into the nasopharynx, oropharynx, and laryngopharynx, with associated tonsils and the opening of the auditory tube. Lower structures include the larynx with the epiglottis, vocal and vestibular folds, thyroid and cricoid cartilages, and the hyoid bone.
Figure 21.5
The image shows the anatomy of the larynx in anterior and right lateral views. Major structures include the epiglottis, thyroid cartilage (with the laryngeal prominence), cricoid cartilage, and tracheal cartilages. Supporting membranes and ligaments include the thyrohyoid membrane, cricothyroid ligament, and cricotracheal ligament. The lateral view also shows the arytenoid, corniculate, and cuneiform cartilages as well as the vestibular and vocal folds, which are essential for voice production and airway protection.
Figure 21.15
The image illustrates lung volumes and capacities. Panel A shows a spirogram with labelled volumes: tidal volume, representing air exchanged during normal breathing; inspiratory reserve volume, the extra air that can be inhaled; expiratory reserve volume, the extra air that can be exhaled; and residual volume, the air remaining in the lungs after maximal exhalation. Panel B combines these volumes into capacities: inspiratory capacity, functional residual capacity, vital capacity, and total lung capacity, showing how different lung volumes sum together to form the total capacity of the lungs.
Figure 21.16
The image illustrates the neural control of breathing. It shows the brain stem regions involved, including the medulla and pons, with the medulla containing the ventral and dorsal respiratory groups (VRG and DRG) and the pons containing the pontine respiratory group (PRG), which includes the pneumotaxic and apneustic centres. Arrows indicate how these centres send stimulatory and inhibitory signals to regulate the diaphragm, external and internal intercostal muscles, and accessory respiratory muscles, coordinating inspiration and expiration.
Figure 21.17
The image illustrates Dalton’s law of partial pressures. It shows three containers: one containing only oxygen molecules with a pressure of 159 millimetres of mercury, one containing only nitrogen molecules with a pressure of 597 millimetres of mercury, and one containing a mixture of oxygen and nitrogen molecules with a total pressure of 756 millimetres of mercury. The combined pressure in the mixed gas equals the sum of the partial pressures of oxygen and nitrogen, demonstrating that the total pressure of a gas mixture is the sum of the pressures each gas would exert independently.
Figure 22.1
The diagram shows the human digestive system, labelling major organs and glands. Starting from the mouth, it includes the tongue, salivary glands (parotid, sublingual, and submandibular), pharynx, and esophagus, leading to the stomach. Connected organs include the liver, gallbladder, and pancreas. The intestines are divided into the small intestine (duodenum, jejunum, and ileum) and the large intestine (cecum, ascending, transverse, descending, and sigmoid colon), ending with the rectum, anal canal, and anus.
Figure 22.2
The diagram shows a cross-section of the gastrointestinal tract wall, highlighting its layers and structures. The innermost mucosa includes the epithelium, lamina propria, and muscularis mucosae surrounding the lumen, with glands and lymphatic tissue. The submucosa contains glands, the submucosal plexus (plexus of Meissner), and blood and lymphatic vessels. The muscularis layer has circular and longitudinal muscles with the myenteric plexus between them. The outermost serosa consists of areolar connective tissue and epithelium, with the mesentery containing arteries, veins, and nerves.
Figure 22.3
The diagram shows a cross-section of the abdominal cavity, identifying major organs and the peritoneal membranes. The spinal cord and vertebra are located posteriorly, with kidneys on either side, the liver and gallbladder on the left, and the spleen on the right. The pancreas lies behind the stomach, while the large and small intestines fill the central area. The visceral peritoneum covers organs, the parietal peritoneum lines the body wall, and the peritoneal cavity lies between them.
Figure 22.5
The diagram illustrates the digestive process from ingestion to defecation. Food enters through the mouth, passes the pharynx and esophagus to the stomach, and moves through the small and large intestines to the anus. Key functions are labelled: propulsion (swallowing and peristalsis), mechanical digestion (chewing, churning, and segmentation), chemical digestion (enzyme breakdown), and absorption (nutrients and water into blood and lymph vessels). The process ends with feces expelled during defecation.
Figure 22.6
The diagram shows an anterior view of the oral cavity with key structures labelled. It includes the superior and inferior lips connected by the labial frenula, gingivae (gums), and teeth (incisors, canines, premolars, and molars). The hard and soft palates form the roof, ending in the uvula. The palatoglossal and palatopharyngeal arches frame the fauces, with the palatine tonsil between them. The tongue is shown with its underside and lingual frenulum, along with the openings of the submandibular gland ducts.
Figure 22.14
The diagram shows the anatomy of the stomach, labelling its major regions and muscular layers. The stomach connects to the esophagus at the cardia and to the duodenum at the pyloric sphincter. The main sections include the fundus, body, pyloric antrum, and pyloric canal. The inner mucosa features folds called rugae, while the muscularis externa consists of three layers—longitudinal, circular, and oblique—that aid in churning and mixing food. The stomach’s curvatures include the lesser curvature on the inner edge and the greater curvature on the outer edge.
Figure 22.15
The diagram shows the microscopic structure of the stomach wall, illustrating its four main layers: mucosa, submucosa, muscularis externa, and serosa. The mucosa contains surface epithelium, lamina propria, and muscularis mucosae, with gastric pits leading into gastric glands. These glands contain parietal cells that secrete hydrochloric acid, chief cells that produce pepsinogen, and enteroendocrine cells that release hormones. The muscularis externa includes oblique, circular, and longitudinal layers for churning and mixing, while the serosa forms the outer covering.
Figure 22.16
The diagram illustrates the three phases of gastric secretion regulation: cephalic, gastric, and intestinal. In the cephalic phase, the sight, thought, or smell of food activates the cerebral cortex and vagus nerve to stimulate gastric secretions, while loss of appetite or depression inhibits them. During the gastric phase, stomach distension and food chemicals trigger local and vagovagal reflexes and gastrin release, enhancing secretion, whereas excessive acidity or emotional stress inhibits it. In the intestinal phase, partially digested food in the duodenum briefly stimulates gastrin release, followed by inhibition through enterogastric reflexes and intestinal hormones such as secretin and cholecystokinin.
Figure 22.18
The image shows the structural organization of the small intestine, emphasizing its adaptations for nutrient absorption. Panel A illustrates the intestinal wall with circular folds, villi, and microvilli that increase surface area. Each villus contains blood vessels and a lacteal for nutrient and fat absorption, along with goblet cells for mucus secretion. The intestinal crypts and duodenal glands lie beneath the mucosal surface. Panels B and C show microscopic images of villi in tissue sections, while D displays the microvilli forming the brush border under high magnification.
Figure 22.20
The image shows the anatomy of the large intestine, labelling its major regions and structures. It begins where the ileum of the small intestine joins the cecum, which includes the vermiform appendix. From there, the ascending colon travels upward to the right colic (hepatic) flexure, across as the transverse colon, and down the descending colon to the sigmoid colon, rectum, and anal canal. The diagram highlights the large intestine’s looping path around the abdominal cavity, connecting to the rectum at the lower end for waste elimination.
Figure 22.21
The image shows the structure of the large intestine. Panel A illustrates a section of the intestinal wall, showing deep intestinal glands (crypts) lined with absorptive cells that take in water and goblet cells that secrete mucus. The mucosa includes lymphatic nodules for immune defence, supported by smooth muscle fibres, the muscularis mucosae, and the submucosa. The inset diagrams highlight microvilli on absorptive cells and mucus-filled goblet cells. Panel B presents a microscopic view of the large intestine’s lining, showing tightly packed tubular glands and numerous mucus-secreting goblet cells.
Figure 22.23
The image shows the liver, gallbladder, pancreas, and associated ducts in relation to the digestive system. The liver is divided into four lobes—right, left, caudate, and quadrate. The right and left hepatic ducts merge to form the common hepatic duct, which joins the cystic duct from the gallbladder to create the common bile duct. This duct carries bile to the duodenum. The pancreas, located below and behind the stomach, connects via the pancreatic duct, which also empties into the duodenum. The spleen, shown to the left of the stomach, lies adjacent to the pancreas.
Figure 22.24
The image illustrates the microscopic structure of the liver, focusing on the hepatic lobules and blood flow. Each lobule is a hexagonal unit composed of plates of hepatocytes radiating from a central vein. Blood enters the lobule from branches of the portal vein and hepatic artery (portal venules and arterioles) located at the corners of the lobule. This blood flows through sinusoids—capillary-like channels—toward the central vein, where it eventually drains into the hepatic vein via the interlobular vein. Bile produced by hepatocytes flows in the opposite direction, from the centre toward bile ducts at the periphery. Connective tissue surrounds the lobules, and the overall organization allows efficient processing of blood and secretion of bile.
Figure 22.25
The image shows the structure and function of the pancreas, highlighting both its exocrine and endocrine components. The pancreas is divided into a head, body, and tail, with a central pancreatic duct that joins the common bile duct before emptying into the duodenum. The exocrine portion consists of lobules made up of acinar cells, which secrete digestive enzymes into the pancreatic ducts. These enzymes are essential for breaking down fats, proteins, and carbohydrates in the small intestine. The endocrine portion is represented by pancreatic islets, which contain hormone-secreting cells that release insulin, glucagon, and other hormones into the bloodstream to regulate blood glucose levels.
Figure 22.26
The image shows the gallbladder and its relationship with the liver and bile ducts. The gallbladder, located beneath the liver, is divided into three regions: the neck, body, and fundus. It stores and concentrates bile produced by the liver. Bile travels through the left and right hepatic ducts, which merge to form the common hepatic duct. The cystic duct connects the gallbladder to this duct, allowing bile to flow in and out of the gallbladder. When needed for digestion, especially after eating fatty foods, bile moves from the gallbladder through the cystic duct into the common bile duct, which delivers it to the small intestine for fat emulsification.
Figure 22.27
The illustration shows the human digestive tract and highlights the key digestive processes occurring at different stages. In the mouth, mechanical digestion involves chewing and swallowing, while chemical digestion begins with the breakdown of carbohydrates and fats. In the stomach, mechanical digestion continues through peristaltic mixing and propulsion, and chemical digestion targets proteins and fats; lipid-soluble substances like alcohol and aspirin are also absorbed here. The small intestine carries out mechanical digestion through segmentation; chemical digestion of carbohydrates, fats, polypeptides, and nucleic acids; and absorption of peptides, amino acids, glucose, fructose, fats, water, minerals, and vitamins. Finally, in the large intestine, mechanical digestion involves segmental mixing and propulsion, chemical digestion is limited to bacterial activity, and absorption focuses on ions, water, minerals, vitamins, and organic molecules.
Figure 22.28
The diagram illustrates the enzymatic breakdown of complex carbohydrates such as starch and glycogen into monosaccharides during digestion. Salivary amylase initiates this process by breaking starch and glycogen into short-branched polysaccharides (limit dextrins) and disaccharides like maltose, sucrose, and lactose. Limit dextrins are further digested by alpha-dextrinase into glucose. Maltose is split by maltase into two glucose molecules, sucrose is broken down by sucrase into one glucose and one fructose molecule, and lactose is digested by lactase into one glucose and one galactose molecule. The final products of carbohydrate digestion are monosaccharides—glucose, fructose, and galactose—that can be absorbed by the body.
Figure 22.29
A diagram illustrates the process of protein digestion and absorption in the human body. Protein digestion begins in the stomach, where hydrochloric acid and the enzyme pepsin break down proteins. Protein-digesting enzymes secreted from the pancreas enter the small intestine, which is the major site of protein digestion and where final digestion occurs. Additional protein-digesting enzymes are secreted from the brush border of the small intestine. Absorbed amino acids enter the bloodstream and travel to the liver, which regulates their distribution throughout the body. A small amount of dietary protein is lost in the feces. The diagram labels the liver, stomach, pancreas, and small intestine to indicate their roles in protein digestion and absorption.
Figure 22.30
This diagram illustrates water input, secretion, and reabsorption throughout the digestive system. It shows that about 2,000 milliliters of water enters the system through food and drink, while digestive secretions contribute additional fluids: 1,500 milliliters from saliva, 1,500 milliliters from gastric secretions, 1,000 milliliters of bile from the liver, 1,000 milliliters of pancreatic juice, 2,000 milliliters from intestinal secretions, and 200 milliliters from colonic mucus. Together, these total approximately 9,000 milliliters entering the small intestine. Of this, the small intestine reabsorbs about 7,800 milliliters, leaving around 1,200 milliliters to pass into the large intestine. The colon reabsorbs about 1,250 milliliters, with roughly 150 milliliters of water lost in the feces. The diagram emphasizes how most water is reclaimed during digestion, with minimal loss.
Figure 22.31
This diagram shows the absorption and transport of lipids in the small intestine. Fat digestion produces fatty acids and monoglycerides, which form micelles in the intestinal lumen. These micelles move into absorptive epithelial cells, where fatty acids and monoglycerides recombine to form triglycerides. Inside the Golgi apparatus, triglycerides combine with proteins to form chylomicrons. These chylomicrons are then released from the epithelial cells into lacteals, specialized lymphatic capillaries. Finally, lymph in the lacteals carries the chylomicrons away from the intestine, integrating them into the lymphatic and circulatory systems.
Figure 23.1
The electron transport chain is shown across the inner mitochondrial membrane, with four protein complexes (I to IV) transferring electrons from NADH and FADH2 and pumping hydrogen ions (H plus) into the intermembrane space. Cytochrome c (Cyt c) carries electrons between complexes III and IV. The accumulated H plus ions flow back into the mitochondrial matrix through ATP synthase, a large enzyme, driving the conversion of ADP and phosphate into ATP. Oxygen serves as the final electron acceptor, combining with electrons and hydrogen ions to form water. The mitochondrial matrix is labelled below the membrane, and the intermembrane space is labelled above it.
Figure 23.2
A flowchart illustrates cellular respiration and ATP production from one glucose molecule through four main stages. In glycolysis, a six-carbon glucose splits into two three-carbon pyruvate molecules, producing 2 ATP (net) and 2 NADH, with 2 ATP used and 4 ATP generated. During pyruvate’s transformation into acetyl CoA, each pyruvate releases CO2 and generates 1 NADH, for a total of 2 NADH. In the Krebs cycle, each acetyl CoA produces 1 ATP, 3 NADH, and 1 FADH2 per cycle, totalling 2 ATP, 6 NADH, and 2 FADH2 for both pyruvates. The electron transport chain uses these 10 NADH and 2 FADH2 to drive redox reactions, producing about 34 ATP through oxidative phosphorylation. Overall, cellular respiration yields about 36 ATP per glucose molecule after accounting for 2 ATP used to transport NADH into mitochondria.
Figure 23.3
A detailed diagram shows the structure of a lipoprotein particle, highlighting its main components. The outer shell is composed of a phospholipid monolayer represented by spherical molecules, which provides a hydrophilic surface that allows the particle to travel in blood. Embedded within this outer layer are apolipoproteins, shown as large blue structures, which serve roles in recognition and transport. Inside the particle, the hydrophobic core contains triglycerides illustrated as yellow branched structures, storing and transporting lipids through the circulatory system.
Figure 23.4
Diagram of the digestive system highlighting enzyme and hormone secretion sites. The esophagus leads to the stomach, where stomach cells secrete pepsin and hydrochloric acid (HCl) for protein digestion. The pancreas connects to the small intestine and releases trypsin, chymotrypsin, elastase, and sodium bicarbonate from its acinar cells to aid digestion and neutralize stomach acid. Intestinal cells secrete secretin and cholecystokinin (CCK), hormones that regulate pancreatic secretion and digestive activity. A magnified inset shows pancreatic ducts delivering enzymes into the small intestine, where most digestion occurs, and the pathway continuing to the large intestine for waste elimination.
Figure 23.5
Diagram illustrating nutrient absorption and insulin action during the absorptive state. Digested nutrients enter the bloodstream, raising blood glucose levels, which triggers insulin release from the pancreas. Insulin promotes glucose uptake by liver, muscle, and adipose cells. In the liver, glucose is converted to glycogen and amino acids are used for ketogenesis. Muscle cells store glucose as glycogen and use amino acids for actin and myosin synthesis. Adipose cells store excess lipids, increasing fat reserves. These processes lower blood glucose and restore homeostasis.
Figure 23.6
This diagram illustrates the postabsorptive state, which occurs when no nutrients are entering the bloodstream from the digestive system. As blood glucose levels decline, the pancreas stops releasing insulin and begins secreting glucagon. Glucagon signals different tissues to mobilize stored energy: In liver cells, glycogen is broken down into glucose, and ketone oxidation helps generate ATP; in muscle cells, glycogen is broken down and proteins are catabolized into amino acids, which can contribute to glucose and ATP production; and in adipose tissue, stored lipids are released and used for glucose, ketone body, or ATP production. These processes collectively help restore and maintain blood glucose levels.
Figure 23.7
Diagram showing the feedback mechanisms of body temperature homeostasis. When body temperature drops below the normal range (36.5 to 37.5°C), temperature receptors in the hypothalamus activate heat-producing mechanisms: Superficial arteries constrict to reduce heat loss, blood flow to the digestive system decreases, shivering increases muscle respiration, and thyroid activity raises metabolic heat production, all of which increase body temperature back to normal. Conversely, when body temperature rises above the normal range, temperature receptors trigger heat-releasing mechanisms: Superficial arteries dilate to enhance heat loss, sweating begins, and thyroid activity decreases to reduce metabolic heat production, leading to a decrease in body temperature and restoration of homeostasis.
Figure 24.1
Illustration showing the anatomy of the urinary and reproductive systems in a sagittal section. Panel A depicts the female anatomy, including the uterus, urinary bladder, pubic bone, urethra, clitoris, labium minora, labium majora, ureter, cervix, rectum, vagina, and anus. Panel B shows the male anatomy, including the urinary bladder, pubic bone, ductus deferens, urethra, penis, epididymis, testis, ureter, seminal vesicle, prostate gland, rectum, and anus.
Figure 24.5
Frontal section of a kidney showing its internal anatomy and major structures. The outer cortex surrounds the inner medulla, which is organized into renal pyramids ending in papillae that project into minor calyces. These minor calyces merge into major calyces, which then drain into the renal pelvis, the funnel-shaped structure leading to the ureter. The renal column separates adjacent pyramids. The renal hilum is the entry and exit point for the renal artery, renal vein, and renal nerve. Blood supply is shown branching into interlobar, arcuate, and cortical blood vessels within the kidney. A small inset illustrates the kidneys’ position in the body relative to the spine and adrenal glands.
Figure 24.6
Diagram showing the blood supply of the kidney and nephron. Blood enters through the renal artery, which branches into segmental, interlobar, arcuate, and cortical radiate arteries. The cortical radiate artery gives rise to afferent arterioles that supply the glomerulus, a capillary network where filtration occurs. Blood exits the glomerulus through efferent arterioles, which lead to the peritubular capillaries surrounding the nephron tubules. The blood then drains through cortical radiate, arcuate, and interlobar veins before exiting via the renal vein. The illustration highlights the close association between the nephron and its capillary network, essential for filtration, reabsorption, and secretion.
Figure 24.7
Diagram of a nephron and associated blood vessels, showing the structure and flow of blood and filtrate during urine formation. Blood enters the glomerulus via the afferent arteriole and exits through the efferent arteriole. The glomerulus, enclosed by the glomerular capsule, filters blood into the proximal convoluted tubule. The filtrate then moves through the loop of the nephron, distal convoluted tubule, and collecting duct, where further processing occurs. The peritubular capillary network surrounds the tubules, facilitating reabsorption and secretion, and connects to the interlobular vein. Processed urine collects in the collecting duct and flows into the renal papilla for excretion.
Figure 24.10
Diagram of a renal corpuscle and its associated structures, showing the afferent arteriole bringing blood into the glomerulus and the efferent arteriole carrying blood away. The glomerulus is a network of capillaries surrounded by podocytes that form part of the filtration barrier. The proximal convoluted tubule extends from the renal corpuscle, beginning urine formation. The distal convoluted tubule (DCT) and macula densa are shown adjacent to the afferent arteriole, where specialized juxtaglomerular cells regulate blood pressure and filtration through renin secretion. The renal nerve is also shown influencing arteriole constriction.
Figure 24.11
Diagram of the renin-angiotensin-aldosterone system (RAAS), illustrating how low fluid flow or low sodium concentration sensed by the macula densa triggers juxtaglomerular cells in the kidney to secrete renin. Renin converts angiotensinogen, released by the liver, into angiotensin I, which is then converted to angiotensin II by angiotensin-converting enzyme (ACE) in the lungs. Angiotensin II causes widespread vasoconstriction and stimulates the adrenal cortex to release aldosterone. Aldosterone promotes sodium uptake in the distal convoluted tubule and collecting ducts, while antidiuretic hormone (ADH) increases water reabsorption by inserting aquaporins in the collecting duct, both of which help restore blood volume and pressure.
Figure 24.14
Diagram of solute and water movement along the nephron. Various substances, including glucose, amino acids, proteins, vitamins, ions (Na plus, K plus, Ca2 plus, Mg2 plus, Cl minus, HCO3 minus), water, urea, lactate, and uric acid, are reabsorbed from the filtrate back into the blood, mainly in the proximal convoluted tubule. Additional water and ions are reabsorbed in the loop of Henle and distal convoluted tubule. Substances like H plus, K plus, NH4 plus, urea, creatinine, and some drugs are secreted into the filtrate. Water and urea also move into the collecting duct, contributing to urine formation.
Figure 24.15
Diagram showing reabsorption and transport mechanisms in the proximal convoluted tubule. Sodium (Na plus) is actively transported out of the tubule cell into the interstitial space via the Na plus / K plus pump using ATP, creating a gradient that drives the cotransport of other substances. Chloride (Cl minus), calcium (Ca2 plus), phosphate (PO43 minus), amino acids, and glucose enter the tubule cell along with Na plus through cotransporters. Hydrogen ions (H plus) are exchanged for Na plus, contributing to acid-base balance. Water (H2O) and magnesium ions (Mg2 plus) follow passively by osmosis and diffusion. These substances then move into the bloodstream, aiding in the reabsorption of essential nutrients and ions.
Figure 24.16
Diagram showing bicarbonate reabsorption and hydrogen ion secretion in the proximal convoluted tubule. Sodium (Na plus) is actively transported out of the tubule cell into the interstitial space using ATP, creating a gradient that drives Na plus reabsorption and H plus secretion. In the lumen, secreted H plus combines with bicarbonate (HCO3 minus) to form carbonic acid (H2CO3), which is quickly converted by carbonic anhydrase into water (H2O) and carbon dioxide (CO2). CO2 diffuses into the tubule cell, where it recombines with water to form H2CO3 again, which dissociates into H plus (recycled into the lumen) and HCO3 minus. The newly formed bicarbonate is transported into the bloodstream, helping regulate acid-base balance.
Figure 24.17
Diagram of the loop of Henle showing osmotic gradients and the movement of water, urea, and ions. The descending limb is permeable to water and urea, allowing them to move out into the increasingly concentrated interstitial fluid as osmolality rises from 300 to 1,200 milliosmoles per kilogram. The ascending limb is impermeable to water but actively transports sodium (Na plus) and chloride (Cl minus) ions out into the interstitium, lowering the filtrate’s osmolality from 1,200 at the bottom of the loop to about 100 milliosmoles per kilogram at the top. This countercurrent mechanism helps establish the medullary osmotic gradient essential for urine concentration.
Figure 25.4
This diagram shows a sodium-potassium pump embedded in the cell membrane. In the first step, the pump is opened to the cytosol and closed to the extracellular fluid. First, three sodium ions move into the pump from the cytosol. An ATP molecule binds to the cytosol side of the pump, causing the pump to change shape and open to the extracellular fluid. The pump is now closed to the cytosol. The sodium ions are then released into the extracellular fluid, after which two potassium ions enter the pump. Also at this point, the used ADP detaches from the cytosol side of the pump, leaving a single phosphate attached. The pump then changes shape again so that it closes to the extracellular fluid and again opens to the cytosol. This releases the two potassium ions into the cytosol. The single phosphate also detaches from the pump at this point so that the cycle can start anew. Two bars along the right-hand side of the figure indicate that sodium normally diffuses into the cell down its concentration gradient, while potassium usually diffuses out of the cell down its concentration gradient. Therefore, the sodium-potassium pump is working against these natural concentration gradients.
Figure 25.5
Diagram illustrating fluid exchange across a capillary bed, showing filtration, no net movement, and reabsorption. At the arterial end, net filtration pressure is positive 10 millimetres of mercury, and fluid exits the capillary because capillary hydrostatic pressure (35 millimetres of mercury) exceeds blood colloidal osmotic pressure (25 millimetres of mercury). At the mid-capillary, net filtration pressure is 0 millimetres of mercury, and there is no net movement as pressures are balanced (25 millimetres of mercury each). At the venous end, net filtration pressure is negative 7 millimetres of mercury, and fluid reenters the capillary because capillary hydrostatic pressure (18 millimetres of mercury) is lower than blood colloidal osmotic pressure (25 millimetres of mercury).
Figure 25.6
This diagram shows a carrier protein embedded in the plasma membrane between the cytoplasm and the extracellular fluid. There are several glucose molecules in the extracellular fluid. In the first step, the carrier protein is open to the extracellular fluid and closed to the cytosol. One of the glucose molecules travels from the extracellular fluid into the carrier protein. The protein then changes shape, closing at both ends. This pushes the glucose down into the carrier protein, closer to the cytosol end. The protein then opens on the cytosol side and closes on the extracellular fluid side, allowing the glucose to enter the cytosol.
Figure 25.7
This figure is a top-to-bottom flowchart describing the thirst response. The topmost box of the chart states that there is insufficient water in the body, which has two effects. The left branch of the chart leads to decreased blood volume, which leads to decreased blood pressure. This triggers an increase in angiotensin II. Angiotensin II stimulates the thirst centre in the hypothalamus. On the right branch, insufficient water in the body leads to increased blood osmolality, which causes dry mouth. Increased blood osmolality and dry mouth are sensed by osmoreceptors in the hypothalamus. This stimulates the thirst centre in the hypothalamus to increase thirst, giving a person the urge to drink. Drinking decreases blood osmolality back to homeostatic levels.
Figure 25.9
This diagram depicts a cross-section of the right wall of a kidney collecting tubule. The wall is composed of three block-shaped cells arranged vertically, one on top of the other. The lumen of the collecting tubule is to the left of the three cells. Yellow-coloured urine is flowing through the lumen. There is a small strip of blue interstitial fluid to the right of the three cells. To the right of the interstitial fluid is a cross-section of a blood vessel. Arrows show that water in the urine is entering the left side of the wall cells through aquaporins. The water travels through the cells and then leaves the kidney tubule through additional aquaporins in the right side of the wall cells. The water travels through the interstitial space and enters the blood in the blood vessel. The aquaporins in the wall cells are being released from aquaporin storage vesicles within their cytoplasm.
Figure 25.10
This flowchart shows how potassium and sodium ion concentrations in the blood are regulated by aldosterone. Rising K plus and falling Na plus levels in the blood trigger aldosterone release from the adrenal cortex. Aldosterone targets the kidneys, causing a decrease in K plus release from the kidneys, which reduces the amount of K plus in the blood back to homeostatic levels. Aldosterone also increases sodium reabsorption by the kidneys, which increases the amount of Na plus in the blood back to homeostatic levels.
Figure 25.11
This figure shows the hormone cascade that increases kidney reabsorption of Na plus and water. In the first step, the kidneys release renin into the bloodstream. The bloodstream is depicted with a red arrow pointing from left to right. At the same time, the liver releases angiotensinogen into the blood, which combines with the renin, yielding angiotensin I. The blood flow then leads to the lungs. Within the pulmonary blood, angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II. The blood then flows to the adrenal cortex, where angiotensin II stimulates the adrenal cortex to secrete aldosterone. Aldosterone causes the kidney tubules to increase reabsorption of NA plus and water into the blood.
Figure 25.12
This top-to-bottom flowchart describes the regulation of pH in the blood. The left branch shows acidosis, which is when the pH of the blood drops. Acidosis stimulates brain and arterial receptors, triggering an increase in respiratory rate. This causes a drop in blood CO2 and H2CO3. A drop in these two acidic compounds causes the blood PH to rise back to homeostatic levels. The right branch shows alkalosis, which is when the PH of the blood rises. Alkalosis also stimulates brain and arterial receptors, but these now trigger a decrease in respiratory rate. This causes an increase in blood CO2 and H2CO3, which lowers the PH of the blood back to homeostatic levels.
Figure 25.13
This figure points out the symptoms of acidosis and alkalosis on a silhouette of a human torso. The effects of acidosis on the central nervous system include headache, sleepiness, confusion, loss of consciousness, and coma. The effects of acidosis are given on the left side of the diagram. The effects of acidosis on the respiratory system include shortness of breath and coughing. The effects of acidosis on the heart include arrhythmia and increased heart rate. The effects of acidosis on the muscular system include seizures and weakness. The effects of acidosis on the digestive system include nausea, vomiting, and diarrhea. The right side of the diagram describes the symptoms of alkalosis. The effects of alkalosis on the central nervous system include confusion, light-headedness, stupor, and coma. The effects of alkalosis on the peripheral nervous system include hand tremor and numbness or tingling in the face, hands, and feet. The effects of alkalosis on the muscular system include twitching and prolonged spasms. The effects of alkalosis on the digestive system include nausea and vomiting.
Figure 26.1
Illustration of the male reproductive system showing an uncircumcised penis with the prepuce (foreskin) and scrotum, a circumcised penis with the foreskin removed to expose the glans penis and corona, and a lateral view of the male reproductive system, including the prostate gland, urinary bladder, pubic symphysis, corpus cavernosum, corpus spongiosum, external urethral opening, ductus (vas) deferens, testis, epididymis, scrotum, spongy urethra, membranous urethra, muscles of the perineum, bulbourethral gland, ejaculatory duct, seminal vesicle, ampulla of the ductus deferens, and suspensory ligament of the penis.
Figure 26.4
Diagram illustrating spermatogenesis and a cross-section of a seminiferous tubule. On the left, the stages of spermatogenesis are shown: Spermatogonium (2n) undergoes mitosis to form primary spermatocytes (2n), which undergo meiosis I to form secondary spermatocytes (1n), then meiosis II to form spermatids (1n), which differentiate into mature spermatozoa. On the right, a histological cross-section of a seminiferous tubule shows labelled structures, including the lumen, spermatogonia, primary spermatocytes, early spermatids, Sertoli (sustentacular) cells, Leydig (interstitial) cells, peritubular capillary, interstitial tissue, lymphatic capillary, and arteriole.
Figure 26.6
Diagram comparing the penis in flaccid and erect states in both lateral and transverse views. In the flaccid state, the corpora cavernosa and corpus spongiosum are relaxed, cavernosal arteries are narrow, and penile venules and the deep dorsal vein remain uncompressed, allowing blood to exit freely. In the erect state, cavernosal arteries dilate, causing blood to engorge the corporal tissue, which swells and erects the penis. These swellings compress penile veins and venules, restricting blood outflow and maintaining an erection. Labels identify key structures such as the corpora cavernosa, corpus spongiosum, cavernosal arteries, spongy urethra, prepuce, and deep dorsal vein.
Figure 26.7
Diagram illustrating the hormonal regulation of the male reproductive system through the hypothalamic-pituitary-gonadal axis. The hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the anterior pituitary to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH). LH stimulates Leydig (interstitial) cells in the testes to release testosterone, while FSH stimulates Sertoli cells to produce androgen-binding protein (ABP), which binds to testosterone to maintain high local concentrations. Sertoli cells also release inhibin, which negatively feeds back to the anterior pituitary to inhibit FSH release. Testosterone exerts negative feedback on both the hypothalamus and pituitary, reducing further release of GnRH, FSH, and LH. The seminiferous tubules and interstitial spaces are shown as sites of hormone action and sperm development.
Figure 26.8
Diagram of the female reproductive system showing two views. In the lateral view, the bladder, pubic symphysis, mons pubis, urethra, clitoris, labium minora, labium majora, uterus, ovary, fornix of uterus, cervix, rectum, vagina, and anus are labelled, illustrating the relationship of internal and external reproductive organs within the pelvic cavity. In the anterior view, the fimbriae, uterus, uterine tube (oviduct), cervix, vagina, ovary, ovarian ligament, broad ligament, labia minora, and labia majora are shown, highlighting the connections of the ovaries and fallopian tubes to the uterus and their supportive ligaments.
Figure 26.9
Diagram of the vulva showing external and internal structures. On the left, the external anterior view illustrates the prepuce, glans clitoris, labia minora, urethral opening, vaginal opening, labia majora, and anus. On the right, the internal anterolateral view reveals the corpus cavernosum, bulb of vestibule, urethral and vaginal openings, Bartholin’s glands and their ducts, and deeper structures of the clitoris and labia, highlighting both superficial and internal components of the female external genitalia.
Figure 26.10
Diagram illustrating oogenesis, the development of the female gamete. It shows an oogonium (2n) undergoing mitosis to form a primary oocyte (2n), which begins meiosis I but arrests in prophase I before birth. After puberty, meiosis I resumes, producing a secondary oocyte (n) and the first polar body. The secondary oocyte arrests at metaphase II and will only complete meiosis II if penetrated by sperm, producing a mature ovum (n) and a second polar body. The process highlights key meiotic stages, timing before birth and after puberty, and the formation of polar bodies during oocyte development.
Figure 26.11
Diagram showing the stages of folliculogenesis and a detailed view of a secondary follicle. Part A illustrates the progression from a primordial follicle with an oocyte surrounded by cortex cells to a primary follicle with granulosa cells and a forming zona pellucida, then a secondary follicle with developing theca cells, followed by a tertiary follicle with an antrum. The mature follicle ovulates, releasing the oocyte, and the ruptured follicle transforms into the corpus luteum in the ovary. Part B shows a micrograph of a secondary follicle, labelling structures such as the oocyte, its nucleus and nucleolus, the corona radiata, zona pellucida, granulosa cells, developing antrum, theca cells, perifollicular capillaries, ovarian stroma, and cortex, illustrating the cellular organization supporting oocyte development.
Figure 26.12
Diagram illustrating the hormonal regulation of the ovarian cycle, divided into the follicular phase, ovulation, and luteal phase. In the follicular phase, the hypothalamus releases GnRH, stimulating the anterior pituitary to secrete LH and FSH, which promote follicle growth and estradiol production; estradiol causes endometrial thickening and provides negative feedback to inhibit GnRH, FSH, and LH. During ovulation, rising estradiol levels switch to positive feedback, enhancing GnRH, FSH, and LH secretion, with the LH surge triggering ovulation. In the luteal phase, LH stimulates the formation of the corpus luteum, which secretes progesterone to inhibit GnRH, FSH, and LH and maintain the endometrium; when the corpus luteum degenerates, progesterone levels fall, leading to the shedding of the stratum functionalis.
Figure 26.13
Diagram showing the female reproductive system and associated histology. The central illustration depicts the uterus, uterine tubes (oviducts), ovaries, and supporting ligaments. Labelled structures include the infundibulum, ampulla, isthmus, and fimbriae of the uterine tube, as well as the fundus, uterine isthmus, cervix, vagina, broad ligament, ovarian ligament, and suspensory ligament. Blood supply is shown via the ovarian, uterine, and vaginal arteries and veins. Insets provide histological views: on the left, the ovarian cortex with follicles beneath the tunica albuginea; on the right, a section of the uterine wall showing the endometrium, myometrium, and perimetrium layers.
Figure 26.14
Diagram showing the hormonal regulation and phases of the ovarian and uterine cycles during the menstrual cycle. The top panel illustrates follicular development: Primordial follicles mature into primary and secondary follicles, with most undergoing atresia, while one becomes the dominant tertiary follicle by days 1 to 7. The middle panels depict ovarian and uterine cycle phases across a 28-day cycle. The ovarian cycle includes the follicular phase (development of the tertiary follicle), ovulation around day 14, and the luteal phase (formation and regression of the corpus luteum). The uterine cycle shows menses, proliferative, and secretory phases, with the endometrium thickening after menstruation. The bottom panels present hormonal fluctuations: FSH and LH levels peak sharply around ovulation, while estrogen rises during the follicular phase and progesterone peaks in the luteal phase, coordinating follicle development and uterine preparation for possible implantation.
Figure 26.15
This image shows the anatomy and internal structure of the breast and mammary glands. The diagram illustrates the nipple and areola, which contain areolar glands, and highlights the branching lactiferous ducts that transport milk toward the nipple. These ducts expand into lactiferous sinuses, where milk is stored before release. The glandular tissue consists of lobules, which contain alveoli—the small sacs responsible for milk production. Surrounding the glandular tissue is fat tissue, which provides structure and protection, as well as suspensory ligaments that support the breast. The overall flow of milk is shown moving from the alveoli through the ducts and sinuses to exit at the nipple.
Figure 27.1
This image illustrates the process of fertilization, showing three main steps in which sperm interact with the oocyte. In step one, hundreds of sperm are attracted to the corona radiata, the outer layer of granulosa cells surrounding the oocyte, and begin breaking through this barrier as they approach the zona pellucida, a glycoprotein membrane around the egg. Step two shows that contact between sperm and the zona pellucida triggers the acrosome reaction, during which sperm release digestive enzymes that break down the zona’s membrane to expose the oocyte’s plasma membrane. In step three, a single sperm successfully burrows through the corona radiata and zona pellucida, then fuses its plasma membrane with that of the oocyte, releasing its nucleus into the cytoplasm of the oocyte, marking the completion of fertilization. The labelled structures include the acrosome, sperm nucleus, sperm receptors in the plasma membrane, the zona pellucida, the corona radiata, the oocyte cytoplasm, and the plasma membrane.
Figure 27.3
This image illustrates the stages of early human development from fertilization to implantation. It begins with an unfertilized oocyte, which becomes a fertilized oocyte after sperm penetration. The zygote undergoes cleavage, forming a two-cell stage, four-cell stage, and then an eight-cell stage and morula of 16 cells as it travels through the uterine tube. The morula develops into a blastocyst of 70 to 100 cells, consisting of a trophoblast, blastocoel, and inner cell mass. The blastocyst hatches by shedding the zona pellucida, rotates, and implants into the endometrium of the uterus, marking the beginning of pregnancy.
Figure 27.4
This diagram illustrates the stages of implantation in the uterus. In step one, the blastocyst begins implantation by digesting the uterine mucosa and embedding itself into the endometrium. In step two, the endometrium grows over and surrounds the embryo, securing it within the uterine lining. In step three, the implanted embryo continues to develop within the endometrium, shown here at seven to eight weeks after conception. The inset shows that implantation most commonly occurs on the posterior uterine wall, with both anterior and lateral views provided.
Figure 27.5
Diagram showing an implanted blastocyst in the endometrium, highlighting key structures of early development. The trophoblast consists of an outer syncytiotrophoblast layer and an inner cytotrophoblast layer, anchoring the embryo to the uterine lining. Inside, the embryonic disc is made up of the epiblast and hypoblast, with the amnion forming around the amniotic cavity above the epiblast. The blastocyst cavity, which will become the yolk sac, is shown adjacent to the hypoblast.
Figure 27.6
Two-panel diagram illustrating gastrulation. The top panel shows a blastocyst implanted in the endometrium with reestablished uterine mucosa, trophoblast, hypoblast, epiblast, and the amniotic cavity. The bottom panel shows the formation of three germ layers: ectoderm from the epiblast, mesoderm forming as cells migrate through the primitive streak, and endoderm as migrating cells displace most of the hypoblast. Insets highlight a cross-section at the primitive streak where these layers develop.
Figure 27.7
Diagram showing a cross-section of an early embryo implanted in the endometrium, surrounded by extraembryonic membranes. The amniotic cavity, filled with fluid, encloses the embryo, with the amnion and yolk sac lined with endoderm. The chorion, derived from the blastocyst membrane, connects to the maternal blood pool, and the allantois is visible near the base. Insets summarize the three germ layers and their derivatives: The endoderm forms the digestive system, liver, pancreas, and lung inner layers; the mesoderm forms the circulatory system, skeletal system, muscular system, and lung epithelial layers; and the ectoderm forms hair, nails, skin, and the nervous system.
Figure 27.8
Cross-section diagram of an implanted embryo in the uterus showing the developing placenta and associated structures. The image labels the yolk sac, amniotic fluid, amnion, chorion, and placenta, with the umbilical cord connecting the embryo to the placenta. A close-up of the placental interface shows chorionic villi extending into maternal blood in the intervillus space, with uterine arteries and veins supplying the area. The umbilical vein and arteries are labelled, illustrating nutrient and gas exchange between maternal and fetal blood.
Figure 27.9
Diagram showing fetal circulation, including the placenta, umbilical cord, and fetal heart. Oxygenated blood from the placenta enters the fetus through the umbilical vein and bypasses the liver via the ductus venosus to reach the inferior vena cava. Blood enters the right atrium, where the foramen ovale allows it to pass directly into the left atrium, bypassing the lungs. The ductus arteriosus connects the pulmonary artery to the aorta, diverting blood away from the lungs. Mixed blood circulates to the fetal body and returns to the placenta through the umbilical arteries.
Figure 27.12
Diagram showing the three stages of childbirth. Stage one is dilation, with the cervix expanding from closed to fully dilated at over 10 centimetres as the amniotic fluid surrounds the fetus. Stage two is birth, showing four steps—the head presenting through the birth canal, rotation and delivery of the anterior shoulder, delivery of the posterior shoulder, and delivery of the lower body and umbilical cord. Stage three is afterbirth, where the placenta detaches from the uterine wall and exits through the vagina, shown alongside a photo of a delivered placenta in a medical tray.
Figure 27.13
Diagram showing circulatory changes before and after birth. Before birth, the ductus arteriosus connects the pulmonary artery to the aorta, and the foramen ovale allows blood to flow between the atria. Immediately after birth, the ductus arteriosus constricts so blood from the right ventricle travels to the lungs, and the foramen ovale closes, forming the fossa ovalis and separating oxygenated and deoxygenated blood. Before birth, the ductus venosus shunts oxygenated blood from the umbilical vein toward the heart, bypassing the liver. After birth, the ductus venosus degenerates into the ligamentum venosum, the inferior vena cava carries only deoxygenated blood, and the umbilical vessels become ligaments.
Figure 27.14
Diagram illustrating the milk ejection reflex during breastfeeding. Suckling by an infant triggers sensory nerve impulses in the areola, which travel to the hypothalamus and stimulate the posterior pituitary to release oxytocin. Oxytocin causes myoepithelial cells around mammary alveoli to contract, pushing milk into the lactiferous ducts. Milk pools in the lactiferous sinuses before being released through nipple pores. Increased milk production stimulates more suckling, forming a positive feedback loop.