Abdomen The front and lateral surface of the torso between the rib cage and the pelvis.
Abdominal Has to do with the region below the rib cage and above the pelvis, to the cavity below the respiratory diaphragm and above the pelvic cavity, to the organs within that cavity, and to the sheets of superficial muscles that surround the cavity.
Abduction The swinging of the arm or thigh out from the midsagittal plane of the body; also applies to the lateral movement of the scapula; opposite of adduction.
Abductor Any muscle that swings an extremity out from the midsagittal plane of the body.
Acetabulum The socket of the hip joint; forms a deep concavity that accommodates the head of the femur.
Acute angles Those between 0° and 90°.
Adduction The drawing together of the thighs, the dropping down of the arm from an outstretched position, and the medial movement of the scapula; opposite of abduction.
Adductor Any muscle that pulls certain segments of an extremity in from a relatively outstretched position.
Aerobic Literally, the presence of oxygen; during aerobic exercise, the heart and lungs are mildly stressed but are capable of supplying the muscles with enough oxygen to keep up with their requirements; contrast with anerobic.
Agonist A muscle that assists another one in some action; opposite of antagonist.
Anal triangle The anatomical region defined by three lines, one between the two ischial tuberosities (this boundary is shared with the urogenital triangle), and two between each of those bumps and the tip of the sacrum and coccyx; see also urogenital triangle.
Anatomical position Standing upright with the forearms supinated (palms facing the front).
Anerobic (or anaerobic) Literally, an absence of oxygen; an anerobic muscular effort requires more oxygen than can be supplied (over a short period of time) to a muscle or group of muscles by the cardio-respiratory system, leading to an oxygen debt in the muscle that is paid after the activity ceases; contrast with aerobic.
Ankylosis Complete or partial fusion of a joint which had once been a movable synovial joint.
Annulus fibrosus The circular connective tissue sheath that makes up most of an intervertebral disk.
Antagonist A muscle that opposes the function of another muscle on the opposite side of a bone, often by restraining movement at a joint; opposite of agonist.
Anterior A directional term meaning toward the front of the body while standing in an upright posture with the palms of the hands facing forward.
Appendicular skeleton The bones of the upper and lower extremities; see upper and lower extremities for the specific bones; contrast with axial skeleton.
Arm The segment of the upper extremity between the shoulder and the elbow.
Articulate To form a joint.
Articular processes Little protrusions of bone that form joints between adjacent vertebral arches.
Articulation Any joint, either a movable synovial joint, a fibrous joint, or a suture.
Atrium, or atria (plural) The chambers of the heart on the right and on the left that receive blood from the vena cava (right side) and the pulmonary vein (left side).
Autonomic nervous system, or ANS The part the nervous system that controls internal organs and that operates more or less autonomously; see also sympathetic and parasympathetic nervous systems.
Axial Has to do with a central axis, either the axial skeleton of the body or an axial line through some segment of an extremity.
Axial skeleton The skeletal support for the body as a whole and for the head, neck, and torso in particular; includes the skull (cranium and mandible), seven cervical vertebrae, twelve thoracic vertebrae, twenty-four ribs (twelve on each side), the sternum, five lumbar vertebrae, the sacrum, and the coccyx; contrast with appendicular skeleton.
Axilla The region of the armpit and the deep structures within.
Axon The cellular process of a neuron that transmits nerve impulses from the cell body to the axon terminals.
Bone One of the connective tissues; contains extracellular bone salts (hydroxyapatite) that make it hard, extracellular connective tissue fibers that make it strong, and living cells that support the extracellular components.
Brachial plexus A plexus of peripheral nerves that supplies the upper extremity; derived from spinal nerves between C4 and T1; see also plexus.
Brain The brain stem, the cerebellum, and the cerebrum; see the separate listings.
Brain stem The continuation of the spinal cord into the brain.
Cartilage One of the connective tissues; contains a specialized extracellular matrix that gives it its characteristic strong but rubbery nature.
Cartilagenous joint A joint without a cavity or synovial fluid; held together by fibrous cartilage.
Cell body The part of the neuron that contains the nucleus; supports the rest of the cell metabolically.
Central nervous system, or CNS The brain and spinal cord; see the separate listings; contrast with peripheral nervous system.
Cerebellum A large segment of the brain located posteriorly to the brain stem and inferiorly to the cerebrum; affects both unconscious reflex activity and willed motor activity.
Cerebrum The largest segment of the brain, composed of the right and left cerebral hemispheres (the right brain and left brain); necessary for willed activity, for conscious appreciation of sensations such as pain, temperature, touch, pressure, vision, audition, taste, and smell, and for the higher functions of the intellect.
Cervical Has to do with the neck, its seven vertebrae and eight bilateral cervical nerves, and its anteriorly convex cervical lordosis.
Circumduction The movement of the arm or thigh in its most extreme circular course.
Coccyx The lowermost segment (the tail bone) of the axial skeleton; composed of a few tiny bones at the bottom of the sacrum.
Concentric Has to do with an ordinary muscle contraction in which the belly of the muscle as a whole shortens; opposite of eccentric.
Connective tissue One of the four primary tissues; includes loose connective tissue, fasciae, tendons, ligaments, cartilage, bone, and blood; see also epithelial, muscle, and nervous tissues.
Contraction Shortening of the individual muscle fibers in a muscle, or activity of the entire muscle; includes eccentric lengthening, concentric shortening, and isometric activity.
Coronal or frontal plane Applies to a vertical, side to side plane, or to some structure that runs in that plane; contrast with sagittal and transverse planes.
Costal Having to do with the ribs.
Counternutation Movement at the sacroiliac joints; moderate slippage in which the top of the sacrum rotates to the rear in relation to the ilia, the coccyx rotates forward, the ilia spread laterally, and the ischial tuberosities move medially; opposite of nutation.
Cross-sectional or transverse plane A plane perpendicular to the vertical axis of the body or of an extremity.
Crural Having to do with the crus, or the crura.
Crus, or crura (plural) Literally “leg”; the portion of the diaphragm (on both the right and left sides) that attaches between the central tendon of the diaphragm and the lumbar spine.
Deep A directional term meaning beneath the surface of the body; opposite of superficial.
Dendrites The cellular processes of neurons that are specialized to receive information from other neurons (from interneurons and motor neurons) or from the environment (from sensory neurons).
Denervate (or more rarely, enervate) To isolate from the nerve supply; usually applied to cutting a motor nerve to a muscle.
Dens See odontoid process.
Diaphragm The respiratory diaphragm and the pelvic diaphragm; see those listings.
Distal A directional term meaning toward the fingers or toes; opposite of proximal.
Diastolic Has to do with the time between ventricular contractions when the right and left ventricles are filling with blood; if the blood pressure is 120/80, the diastolic pressure is 80 mm Hg; opposite of systolic.
Eccentric lengthening A type of muscle contraction in which the belly of the muscle as a whole lengthens but at the same time resists lengthening, always against the force of gravity; opposite of concentric.
Enteric nervous system The component of the autonomic nervous system that lies embedded in the wall of the gut and that allows the gut to function independently.
Epithelial tissue One of the four primary tissues; forms the boundary between the external world and the internal environment of muscle and connective tissue; see also connective tissue, muscle tissue, and nervous tissue.
Extension The unfolding of a limb or straightening of the trunk from a flexed position; opposite of flexion.
Extensor muscles Act generally to extend, or unfold, the joints of the upper and lower extremities; antagonists to the flexors.
Extra- Outside of, especially outside of cells; includes everything non-cellular deep to the outermost surface of the skin; contrast with inter- and intra-.
Extremity, or appendage Either the upper or lower extremity; contains the appendicular skeleton, as opposed to the axial skeleton; see also upper extremity, lower extremity, appendicular skeleton, and axial skeleton.
Facet A small smooth region of a bone covered with articulating cartilage for forming a joint (always a gliding joint) with another bone.
Facilitation Input from axon terminals of other neurons that increases activity in the neurons on which the axon terminals impinge; produces an increase in the number of nerve impulses per second that travel down the axon of the affected neuron; opposite of inhibition.
Facilitatory Tending to induce facilitation.
Fascia Sheets of connective tissue (fibers and cells) that support and give form to organs and muscles throughout the body.
Fibrocartilage A specialized connective tissue containing a combination of connective tissue fibers and cartilage.
Fibrous Has to do with joints of that type, to dense connective tissue that makes up the capsule of joints, and to the substance of fasciae that surrounds muscle.
Fibrous joint One in which no joint cavity is present and where heavy concentrations of fibrous connective tissue hold the joint together.
Flexion The folding in of a limb; opposite of extension.
Flexor muscles Act generally to fold the joints; antagonists to the extensors.
Forearm The segment of the upper extremity between the elbow and the wrist.
Frontal plane See coronal plane.
Hip bone See pelvic bone.
Hyaline cartilage Found on the surface of long bones of the extremities; facilitates movement of synovial joints.
Hyperextension Extension beyond the norm.
Hyperventilation Overbreathing to the extent of creating a subjective level of discomfort; results in elevated levels of blood oxygen and lowered levels of blood carbon dioxide.
Hypoventilation Underbreathing; results in lowered levels of blood oxygen and abnormally high levels of carbon dioxide.
Ilium One of three segments of the hip bone; the large wing-shaped portion that articulates posteriorly with the sacrum to complete the pelvic bowl.
Inferior A directional term meaning toward the feet or below the head; opposite of superior.
Inferior articulating processes Small bony processes that extend inferiorly from the junction of the pedicle and lamina on both sides of a vertebral arch; in combination with the superior articulating processes of the next lower vertebra, the superior articulating processes form small, gliding-type facet joints.
Inferior pubic rami Wing-like extensions of the pubic bones that run inferiorly, posteriorly, and laterally from the region of the pubic symphysis to the ischial tuberosities.
Inhibition Input to neurons from axon terminals that decreases activity in the neurons on which the axon terminals impinge; produces a decrease in the number of nerve impulses per second that travel down the axon of the affected neuron; opposite of facilitation.
Inhibitory Tending to induce inhibition.
Innervate The nerve supply to a structure, as when a motor nerve innervates a muscle.
Inter- Between, especially between cells, as in intercellular substances or spaces; contrast with extra- and intra-.
Intercostal nerves Branches of spinal nerves T1-12 that supply intercostal (between the ribs) muscles and abdominal muscles.
Interneuron or association neuron Any neuron that is interposed between a motor neuron and a sensory neuron.
Intervertebral disks Cylindrically-shaped segments of fibrocartilage that link adjacent vertebral bodies; they contain a central liquid core (the nucleus pulposus) and a superficial annulus fibrosis.
Intervertebral foramina Bilateral gaps in the spine through which spinal nerves emerge carrying mixed spinal (motor and sensory) nerves; motor fibers pass peripherally to make synaptic contact with skeletal muscle, smooth muscle, and glands; sensory fibers pass centrally to bring sensory information into the central nervous system.
Intra- Inside of; refers to nuclei and other organelles within the cell; contrast with extra- and inter-.
Ischial tuberosities The sitting bones; see also ischium.
Ischium One of the three fused-together components of the pelvic bone, the others being the ilium and the pubis; its most inferior surface is the ischial tuberosity.
Isometric contraction A type of muscle contraction in which tension in the muscle increases (as a result of shortening of the individual muscle fibers) but the length of the muscle stays the same, as would happen if you were to try to lift a locomotive.
Isotonic contraction A type of muscle contraction in which individual muscle fibers produce movement about a joint, as in walking, running, and nearly all athletic endeavors.
Joint The region of apposition of two or more bones; same as articulation; includes cartilaginous, fibrous, and synovial joints; see individual listings for details.
Kyphosis A posteriorly convex curvature of the spinal column; the clinical meaning of kyphosis is an excessive thoracic curvature (humpback) that develops in the upper back, often in association with osteoporosis.
Laminae The flattened segments of the vertebral arch between the transverse processes and the spinous process.
Lateral A directional term meaning to the side, using a midsagittal plane as a point of reference.
Leg The segment of the lower extremity between the knee and the ankle.
Lordosis An anteriorly convex curvature of the spinal column; the clinical meaning is an excessive lumbar curvature (swayback) that develops in the lower back.
Lower extremity Includes the pelvic bone and hip joint, the thigh (with femur), knee joint, leg (with tibia and fibula), ankle (with tarsal bones), and feet (with metatarsals and phalanges), as well as all associated muscles, nerves, blood vessels, and skin.
Lumbar Having to do with the lower back, its five vertebrae and five bilateral lumbar nerves, and its anteriorly convex lumbar lordosis.
Lumbosacral plexus A plexus of nerves from L1 to S5 that supplies the lower abdomen, perineum, and lower exremities; see also plexus.
Matrix Substance, material, or content; usually applied here to some extracellular component of connective tissues.
Medial A directional term meaning toward the mid-line, or closer to the midsagittal plane than some other structure.
Meniscus, or semilunar cartilage The medial and lateral menisci are incomplete, donut-shaped wafers of fibrocartilage that cushion the knee joint.
Motor Has to do with output from the motor neurons (located within the central nervous system) to skeletal muscles, smooth muscle, cardiac muscle, and glands throughout the body; contrast with sensory.
Motor neuron One of three classes of neurons (the others are interneurons and sensory neurons); innervates skeletal muscle fibers; counterpart to sensory neurons.
Motor unit A motor neuron (including its dendrites and axon) plus all of the muscle fibers that it supplies.
Muscle fiber, or muscle cell The individual cells in muscle tissue.
Muscle tissue One of the four primary tissues; includes cardiac muscle in the heart, smooth muscle in the walls of internal organs, and skeletal muscle; see also epithelium, connective tissue, and nervous tissue.
Myotatic stretch reflex A reflex contraction of a muscle that occurs as a result of dynamic stretch.
Nervous tissue One of the four primary tissues; specialized for communication; see also epithelium, connective tissue and muscle tissue.
Neuron The genetic, anatomical, and functional unit of the nervous system; a cell that is specialized to receive information from the environment or other cells and to transmit information to other sites, frequently long distances; see motor neuron, interneuron, and sensory neuron.
Nucleus pulposus The liquid core of intervertebral disks; moves posteriorly within the disk during a forward bend, anteriorly during a backbend, to the right when bending left, to the left when bending right, and is compressed during a twist.
Nutation Movement at the sacroiliac joints; a moderate slippage in which the top of the sacrum rotates forward in relation to the ilia, the coccyx rotates to the rear, the ilia move medially, and the ischial tuberosities move laterally; opposite of counternutation.
Obtuse angles Those between 90° and 180°.
Occipital The cranial bone situated behind the parietal bones; located just outside the occipital lobe of the brain.
Odontoid process, or dens The tooth-like process of the axis (C2) around which the atlas (C1) rotates.
Parasympathetic, or vegetative nervous system Supports the day-today functioning of internal organs on an individual basis; contrast with sympathetic nervous system.
Pedicles Segments of vertebral arches; the short columns of bone that extend posteriorly from the vertebral bodies and that continue into the flatter vertebral laminae (which complete the vertebral arch posteriorly).
Pelvic Refers to the two hip bones, to the cavity that is continuous with and below the abdominal cavity, to the diaphragm that defines the base of the torso, or simply to the region of the body vaguely below the abdomen and above the thighs.
Pelvic, or hip bone A single bone (one on each side of the body) formed from three separate bones in the embryo (the ilium, the ischium, and the pubis); the two pelvic bones together with the sacrum form the pelvic bowl.
Pelvic diaphragm A combination of fasciae and muscle that closes off the base of the pelvic bowl and supports the abdominopelvic viscera; the deepest layer of the perineum, on which the genitals are superimposed externally.
Pelvis Includes both pelvic bones; forms the base of the torso, and articulates with the axial skeleton at the two sacroiliac joints.
Pericardial Has to do with the cavity (a potential space only) around the heart whose outer boundary is the fibrous pericardium and which contains a small amount of slippery fluid that allows the heart to expand and contract without trauma; pericardial cavity is comparable to the peritoneal cavity in the abdominopelvic cavity and the pleural cavity that surrounds the lungs.
Pericardium The thin layers of tissue that line the outer surface of the heart (visceral pericardium) and the inner surface of the pericardial cavity (parietal pericardium); also the fibrous pericardium, a heavy connective tissue sack that surrounds the heart and pericardial cavity collectively; see also peritoneum and pleura.
Perineal Having to do with the perineum.
Perineum A diamond-shaped region whose borders are the bottom of the pubic symphysis, the inner borders of the inferior pubic rami and ischial tuberosities, and the sacrotuberous ligaments, which extend between the ischial tuberosities and the inferior tip of the sacrum and coccyx; contains the pelvic diaphragm and all the urogenital structures located within these boundaries; the more common definition is the small region between the anus and the genitals.
Peripheral nervous system, or PNS Includes motor and sensory roots of spinal nerves, spinal nerves, and autonomic plexuses and ganglia, that is, all parts of the nervous system except the brain and spinal cord; contrast with central nervous system.
Peritoneal Has to do with the cavity (a potential space only) between the internal organs of the abdomen and pelvis.
Peritoneum The lining of the peritoneal cavity; includes visceral peritoneum lining the internal organs and parietal peritoneum lining the inner aspect of the body wall; see also pericardium and pleura.
Peroneal nerve (common peroneal nerve) Arises (with the tibial nerve) from the sciatic nerve; has two main branches, the deep peroneal nerve and the superficial peroneal nerve; the latter can be traumatized by sitting intemperately on a hard surface in the adamantine pose.
Phrenic nerve Originates from C3-5; supplies the respiratory diaphragm.
Pleura The lining of the pleural cavity; visceral pleura lines the surfaces of the lungs and parietal pleura lines the inner aspect of the body wall and the upper surface of the respiratory diaphragm; see also peritoneum and pericardium.
Pleural Has to do with the cavity (a potential space only) between the lateral surfaces of the lungs and the inner wall of the chest, and between the base of the lungs and the upper surface of the diaphragm.
Plexus An intertwining and mixing of nerves; the brachial plexus supplies the upper extremity, and the lumbosacral plexus supplies the lower extremity.
Posterior A directional term meaning toward the back of the body while standing in an upright posture with the palms of the hands facing forward; opposite of anterior.
Process A small extension of bone, not as long and prominent as a ramus and not as robust as a trochanter; in the vertebral column, the superior articulating process of one vertebra articulates with the inferior articulating process of the next higher vertebra, forming a small facet joint.
Pronation Rotation of the wrist and hand with reference to the elbow; if you stand and face the palms to the rear, the forearms are pronated; the opposite of supination.
Proximal A directional term referring to portions of the extremities relatively nearer the pelvis and chest than the fingertips and toetips; opposite of distal.
Pubic symphysis A fibrocartilaginous joint that is the site of union of the two pelvic bones.
Pubis, or pubic bone One of the three components of the pelvic bone; also, the superficial region in front of the pubic symphysis, as in the mons pubis.
Pulmonary Having to do with the lungs. The pulmonary circulation is the circuit of blood from the heart (right ventricle) to the lungs and back to the heart (left atrium); counterpart to systemic circulation.
Radius One of the two bones of the forearm; located laterally (on the thumb side) in the anatomical position; see also ulna.
Ramus (plural rami) Literally means “branch.”
Rectus Straight; applied here to the side-by-side, straight up-and-down abdominal muscles, or to the rectus femoris (the straight head of the quadriceps femoris).
Respiratory diaphragm The dome-like sheet of muscle that spans the torso between the chest and the abdomen; its costal portion attaches to the base of the rib cage, and its crural portion (or crus) attaches to the lumbar spine.
Right angle A 90° angle.
Sacral Has to do with the sacrum, as in the posteriorly convex sacral kyphosis and the five bilateral sacral nerves.
Sacrum, or the sacred bone The lowermost major segment of the spine; articulates with the ilium on each side at the sacroiliac joints; five pairs of spinal nerve exit the sacrum.
Sagittal plane A plane that runs through the body in an up-and-down and front-to back orientation; a midsagittal plane bisects the body down the middle, and a parasagittal plane is parallel to the midsagittal plane but to one side; contrast with coronal and transverse planes.
Sciatic nerve The largest nerve of the lumbosacral plexus; its two large branches are the tibial nerve, which supplies the calf muscles on the posterior side of the leg, and the common peroneal nerve, which supplies muscles on the anterior side of the leg.
Semilunar cartilage See meniscus.
Sensory Has to do with conscious and unconscious input from the body to the central nervous system; conscious input includes pain, temperature, touch, pressure, vision, audition, taste, smell; unconscious input includes information for equilibrium and sensory aspects of the autonomic nervous system; also includes associated systems within the central nervous system, especially those that carry the sensory information to consciousness; contrast with motor.
Sensory neuron One of three classes of neurons (the others are interneurons and motor neurons); synapses with interneurons that carry incoming sensory information to consciousness in the cerebral cortex or that take part in unconscious reflexes; counterpart to motor neurons.
Sesamoid bone One that is within a tendon; the largest sesamoid bone in the body is the patella.
Sitting bones See ischial tuberosities.
Solar (coeliac) plexus A major nerve plexus of the autonomic nervous system that lies against the aorta between the diaphragm and the bifurcation of the aorta (illustrated on the cover of this book).
Somatic nervous system Innervates skeletal muscle; receives sensory information from somatic senses such as pain, touch, vision, and audition.
Spinal cord The part of the central nervous system that extends from the brain stem into the vertebral canal; includes twelve thoracic segments, five lumbar segments, five sacral segments, and one coccygeal segment.
Spinal nerve A mixed (motor and sensory) nerve that exits from the spinal cord segmentally in relation to each vertebra; contains both somatic and autonomic components.
Spinous processes Extend posteriorly from each vertebral arch.
Suboccipital The region just inferior to the base of the skull posteriorly.
Superficial A directional term meaning toward the surface; opposite of deep.
Superior A directional term meaning above the feet or toward the head; opposite of inferior.
Superior articulating processes Small bony processes that extend superiorly from the junction of the pedicle and lamina on both sides of a vertebral arch; they form facet joints with the next lower vertebra; see also processes and inferior articulating processes.
Superior pubic rami Wing-like extensions of the pubic bones that run superiorly, posteriorly, and laterally from the region of the pubic symphysis to the ilia.
Supination Rotation of the wrist and hand with reference to the elbow; if you stand and face the palms to the front, the forearms are supinated; opposite of pronation.
Suture A fibrous joint that unites the flat bones of the cranium.
Sympathetic nervous system Supports the whole-body “fight-or-flight” function; gears up certain internal organs and the musculoskeletal system for emergencies; contrast with parasympathetic nervous system.
Symphysis A cartilaginous joint; see also pubic symphysis and intervertebral disk.
Synapse The point of junction between the axon terminal of one neuron and its target, usually either a muscle cell or another neuron.
Synovial fluid A slippery fluid which lubricates synovial joints, facilitating smooth and easy movement of the articulating hyaline cartilage.
Synovial joint A slippery movable joint that contains synovial fluid, a synovial membrane that secretes synovial fluid, slippery articular cartilage on the ends of long bones that contact one another in the joint, and a fibrous joint capsule that protects the surfaces and retains the synovial fluid in the vicinity of the articulating surfaces.
Systemic Refers to the body as a whole; the systemic circulation begins at the left ventricle, leaves the heart in the aorta, flows to the capillaries of the body, and returns to the heart (right atrium) by way of the vena cava; counterpart to pulmonary circulation.
Systolic Has to do with the time during which the ventricles are contracting; if the blood pressure is 120/80, the systolic pressure is 120 mm Hg; opposite of diastolic.
Thigh The segment of the lower extremity between the hip and the knee.
Thoracic Has to do with the thorax, or chest; includes twelve vertebrae and twelve bilateral thoracic nerves, the thoracic cage with twelve ribs on each side and the sternum in front, the posteriorly convex thoracic kyphosis, and the thoracic cavity; this cavity in turn contains the pericardium, heart, and pericardial cavity, as well as the lungs and pleural cavities.
Transverse, or cross-sectional plane A plane through the body that extends both from front to back and from side to side; contrast with coronal and sagittal planes.
Transverse process The bony protuberance (one on each side of each vertebra) that extends laterally from the vertebral arch at the junction of the lamina and the pedicle; see also process.
Trochanter A large bony prominence that represents the sites of muscle attachments.
Tuberosity A bump on a bone that represents the sites of muscle attachments; see also ischial tuberosity.
Ulna One of the two bones of the forearm, located medially (on the little finger side) in the anatomical position; see also radius.
Upper extremity Includes the clavicle, scapula, arm (with humerus), elbow joint, forearm (with radius and ulna), wrist (with carpal bones), hand (with metacarpals and phalanges), as well as all associated muscles, nerves, blood vessels, and skin.
Urogenital triangle The anatomical region defined by three lines, one between the ischial tuberosities (this boundary is shared by the anal triangle), and two between each of those bumps and the inferior border of the pubic symphysis; see also anal triangle.
Vasoconstriction Constriction of blood vessels (usually small arteries and arterioles) caused by sympathetic nervous system input to smooth muscle surrounding the vessel; contrast with vasodilation.
Vasodilation Dilation of blood vessels (usually small arteries and arterioles) caused by biochemical factors and diminished sympathetic nervous system input to the smooth muscle surrounding the vessels; contrast with vasoconstriction.
Ventricles The chambers from which blood is pumped out of the heart; blood is pumped into the pulmonary circuit on the right side and into the systemic circuit on the left side.
Vertebra The bony unit of the vertebral column, or the spine; we have seven cervical vertebrae (C1-7), twelve thoracic vertebrae (Tl-12), five lumbar vertebrae (L1-5), a single fused sacrum with five segments (S1-5), and a rudimentary coccyx; each vertebra contains a vertebral body, a vertebral arch, transverse processes, a spinous process, and superior and inferior articulating processes; see the individual listings.
Vertebral arch Made of up two pedicles and two laminae which meet posteriorly to complete the arch; see also vertebral body, pedicles, laminae, and the inferior and superior articulating processes.
Vertebral body The cylindrically-shaped portion of the vertebra which is separated from its neighbors (one below and one above) by intervertebral disks; see also vertebral arch.
Vertebral canal The tubular portion of the vertebral column (just behind the vertebral bodies) that houses the spinal cord.
Visceral Having to do with the viscera (internal organs) and other related structures such as smooth muscle, cardiac muscle, and glands.