Control center The component of a feedback system, such as the
brain, that determines the point at which a controlled condition,
such as body temperature, is maintained.
Conus medullaris (KO-nus med-u-LAR-is) The tapered portion of the
spinal cord inferior to the lumbar enlargement.
Convergence (con-VER-jens) A synaptic arrangement in which the
synaptic end bulbs of several presynaptic neurons terminate on
one postsynaptic neuron. The medial movement of the two eye-
balls so that both are directed toward a near object being viewed
in order to produce a single image.
Convulsion (con-VUL-shun) Violent, involuntary contractions or
spasms of an entire group of muscles.
Cornea (KOR-ne-a) The nonvascular, transparent fibrous coat
through which the iris of the eye can be seen.
Corona radiata The innermost layer of granulosa cells that is firmly
attached to the zona pellucida around a secondary oocyte.
Coronary artery disease (CAD) A condition such as atherosclerosis
that causes narrowing of coronary arteries so that blood flow to
the heart is reduced. The result is coronary heart disease (CHD), in
which the heart muscle receives inadequate blood flow due to an
interruption of its blood supply.
Coronary circulation The pathway followed by the blood from the
ascending aorta through the blood vessels supplying the heart
and returning to the right atrium. Also called cardiac circulation.
Coronary sinus (ST-nus) A wide venous channel on the posterior
surface of the heart that collects the blood from the coronary
circulation and returns it to the right atrium.
Corpus albicans (KOR-pus AL-bi-kanz) A white fibrous patch in the
ovary that forms after the corpus luteum regresses.
Corpus callosum (kal-LO-sum) The great commissure of the brain
between the cerebral hemispheres.
Corpus luteum (LOO-te-um) A yellowish body in the ovary formed
when a follicle has discharged its secondary oocyte; secretes
estrogens, progesterone, relaxin, and inhibin.
Cortex (KOR-teks) An outer layer of an organ. The convoluted layer
of gray matter covering each cerebral hemisphere.
Costal (KOS-tal) Pertaining to a rib.
Costal cartilage (KAR-ti-lij) Hyaline cartilage that attaches a rib to the
Cramp A spasmodic, usually painful contraction of a muscle.
Cranial cavity (KRA-ne-al) A body cavity formed by the cranial bones
and containing the brain.
Cranial nerve One of 12 pairs of nerves that leave the brain; pass
through foramina in the skull; and supply sensory and motor
neurons to the head, neck, part of the trunk, and viscera of the
thorax and abdomen. Each is designated by a Roman numeral
and a name.
Cranium (KRA-ne-um) The skeleton of the skull that protects the
brain and the organs of sight, hearing, and balance; includes
the frontal, parietal, temporal, occipital, sphenoid, and ethmoid
Creatine phosphate (KRE-a-tin FOS-fat) Molecule in striated muscle
fibers that contains high-energy phosphate bonds; used to gener-
ate ATP rapidly from ADP by transfer of a phosphate group. Also
called phosphocreatine (fos'-fo-KRE-a-tin).
Crenation (kre-NA-shun) The shrinkage of red blood cells into knobbed,
starry forms when they are placed in a hypertonic solution.
Crista (KRIS-ta) A crest or ridged structure. A small elevation in the
ampulla of each semicircular duct that contains receptors for
Crossing-over The exchange of a portion of one chromatid with
another during meiosis. It permits an exchange of genes among
chromatids and is one factor that results in genetic variation of
Cryptorchidism (krip-TOR-ki-dizm) The condition of undescended
Cupula (KUP-u-la) A mass of gelatinous material covering the hair
cells of a crista; a sensory receptor in the ampulla of a semicircu-
lar canal stimulated when the head moves.
Cushing syndrome (KUSH-ing) Condition caused by a hypersecretion
of glucocorticoids characterized by spindly legs, "moon face,"
"buffalo hump," pendulous abdomen, flushed facial skin, poor
wound healing, hyperglycemia, osteoporosis, hypertension, and
increased susceptibility to disease.
Cutaneous (ku-TA-ne-us) Pertaining to the skin.
s) A blue or dark purple discoloration, most eas-
ily seen in nail beds and mucous membranes, that results from an
increased concentration of deoxygenated (reduced) hemoglobin
(more than 5 gm/dL).
Cyclic AMP (cyclic adenosine-3',5'-monophosphate) Molecule
formed from ATP by the action of the enzyme adenylate cyclase;
serves as second messenger for some hormones and neurotrans-
Cyst (SIST) A sac with a distinct connective tissue wall, containing a
fluid or other material.
Cystic duct (SIS-tik) The duct that carries bile between the gallblad-
der and the common bile duct.
Cystitis (sis-TT-tis) Inflammation of the urinary bladder.
Cytolysis (sl-TOL-i-sis)The rupture of living cells in which the con-
tents leak out.
Cytokinesis (sT-to-ki-NE-sis) Distribution of the cytoplasm into two
separate cells during cell division; coordinated with nuclear divi-
Cytoplasm (ST-to-plazm) Cytosol plus all organelles except the
Cytoskeleton (sT'-to-SKEL-e-ton) Complex internal structure of cyto-
plasm consisting of microfilaments, microtubules, and intermedi-
Cytosol (ST-to-sol) Fluid located within cells. Also called intracellular
fluid (ICF) (in'-tra-SEL-u-lar).
Deciduous (de-SID-u-us) Falling off or being shed seasonally or at a
particular stage of development. In the body, referring to the first
set of teeth.
Deep Away from the surface of the body or an organ.