Cardiac notch An angular notch in the anterior border of the left
lung into which part of the heart fits.
Cardiac output (CO) The volume of blood pumped from one ventricle
of the heart (usually measured from the left ventricle) in 1
normally about 5.2 liters/min in an adult at rest.
Cardiology (kar-de-OL-o-je) The study of the heart and diseases
associated with it.
Cardiovascular center (kar-de-o-VAS-ku-lar) Groups of neurons scat-
tered within the medulla oblongata that regulate heart rate, force
of contraction, and blood vessel diameter.
Carotene (KAR-o-ten) Antioxidant precursor of vitamin A, which is
needed for synthesis of photopigments; yellow-orange pigment
present in the stratum corneum of the epidermis. Accounts for
the yellowish coloration of skin. Also termed beta-carotene.
Carotid body (ka-ROT-id) Cluster of chemoreceptors on or near the
carotid sinus that respond to changes in blood levels of oxygen,
carbon dioxide, and hydrogen ions.
Carotid sinus A dilated region of the internal carotid artery just
above the point where it branches from the common carotid
artery; it contains baroreceptors that monitor blood pressure.
Carotid sinus reflex A reflex that helps maintain normal blood pres-
sure in the brain. Nerve impulses propagate from the carotid
sinus baroreceptors over sensory axons in the glossopharyngeal
(IX) nerves to the cardiovascular center in the medulla oblongata.
Carpal bones The eight bones of the wrist. Also called carpals.
Carpus (KAR-pus) A collective term for the eight bones of the wrist.
Cartilage (KAR-ti-lij) A type of connective tissue consisting of chon-
drocytes in lacunae embedded in a dense network of collagen and
elastic fibers and an extracellular matrix of chondroitin sulfate.
Cartilaginous joint (kar'-ti-LAJ-i-nus) A joint without a synovial (joint)
cavity where the articulating bones are held tightly together by
cartilage, allowing little or no movement.
Cast A small mass of hardened material formed within a cavity in the
body and then discharged from the body; can originate in differ-
ent areas and can be composed of various materials.
Catabolism (ka-TAB-o-lizm) Chemical reactions that break down com-
plex organic compounds into simple ones, with the net release of
Cataract (KAT-a-rakt) Loss of transparency of the lens of the eye or its
capsule or both.
Cation (KAT-T-on) A positively charged ion. An example is a sodium
Cauda equina (KAW-da e-KWT-na) A tail-like array of roots of spinal
nerves at the inferior end of the spinal cord.
Cecum (SE-kum) A blind pouch at the proximal end of the large intes-
tine that attaches to the ileum.
Cell The basic structural and functional unit of all organisms; the small-
est structure capable of performing all the activities vital to life.
Cell cycle Growth and division of a single cell into two identical cells;
consists of interphase and cell division.
Cell division Process by which a cell reproduces itself that consists
of a nuclear division (mitosis) and a cytoplasmic division (cytoki-
nesis); types include somatic and reproductive cell division.
Cell-mediated immunity That component of immunity in which
specially sensitized T lymphocytes (T cells) attach to antigens to
destroy them. Also called cellular immunity.
Cementum (se-MEN-tum) Calcified tissue covering the root of a tooth.
Center of ossification (os'-i-fi-KA-shun) An area in the cartilage model
of a future bone where the cartilage cells hypertrophy and then
secrete enzymes that result in the calcification of their matrix,
resulting in the death of the cartilage cells, followed by the inva-
sion of the area by osteoblasts that then lay down bone.
Central canal A microscopic tube running the length of the spinal
cord in the gray commissure. A circular channel running longitu-
dinally in the center of an osteon (haversian system) of mature
compact bone, containing blood and lymphatic vessels and
nerves. Also called a haversian canal (ha-VER-shan).
Central fovea (FO-ve-a) A depression in the center of the macula
lutea of the retina, containing cones only and lacking blood ves-
sels; the area of highest visual acuity (sharpness of vision).
Central nervous system (CNS) That portion of the nervous system
that consists of the brain and spinal cord.
Centrioles (SEN-tre-olz) Paired, cylindrical structures of a centro-
some, each consisting of a ring of microtubules and arranged at
right angles to each other.
Centromere (SEN-tro-mer) The constricted portion of a chromo-
some where the two chromatids are joined; serves as the point
of attachment for the microtubules that pull chromatids during
anaphase of cell division.
Centrosome (SEN-tro-som) A dense network of small protein fibers
near the nucleus of a cell, containing a pair of centrioles and
Cephalic (se-FAL-ik) Pertaining to the head; superior in position.
Cerebellum (ser-e-BEL-um) The part of the brain lying posterior to
the medulla oblongata and pons; governs balance and coordi-
nates skilled movements.
Cerebral aqueduct (SER-e-bral AK-we-dukt) A channel through the
midbrain connecting the third and fourth ventricles and contain-
ing cerebrospinal fluid. Also termed the aqueduct of Sylvius.
Cerebral arterial circle A ring of arteries forming an anastomosis
at the base of the brain between the internal carotid and basilar
arteries and arteries supplying the cerebral cortex. Also called
the circle of Willis.
Cerebral cortex The surface of the cerebral hemispheres, 2-4 mm
thick, consisting of gray matter; arranged in six layers of neuronal
cell bodies in most areas.
Cerebrospinal fluid (CSF) (se-re'-bro-SPT-nalJ A fluid produced by
ependymal cells that cover choroid plexuses in the ventricles of
the brain; the fluid circulates in the ventricles, the central canal,
and the subarachnoid space around the brain and spinal cord.
Cerebrovascular accident (CVA) (se-re'-bro-VAS-ku-lar) Destruction of
brain tissue (infarction) resulting from obstruction or rupture of blood
vessels that supply the brain. Also called a stroke or brain attack.
se-RE-brum) The two hemispheres of the
forebrain (derived from the telencephalon), making up the largest
part of the brain.