Cerumen (se-ROO-men) Waxlike secretion produced by ceruminous
glands in the external auditory meatus (ear canal). Also termed
Ceruminous gland (se-ROO-mi-nus) A modified sudoriferous (sweat)
gland in the external auditory meatus that secretes cerumen (ear
Cervical ganglion (SER-vi-kul GANG-gle-on) A cluster of cell bodies of
postganglionic sympathetic neurons located in the neck, near the
Cervical plexus (PLEK-sus) A network formed by nerve axons from
the ventral rami of the first four cervical nerves and receiving gray
rami communicates from the superior cervical ganglion.
Cervix (SER-viks) Neck; any constricted portion of an organ, such as
the inferior cylindrical part of the uterus.
Chemical bond Force of attraction in a molecule or compound that
holds its atoms together. Examples include ionic and covalent bonds.
Chemical element Unit of matter that cannot be broken apart into
a simpler substance by ordinary chemical reactions. Examples
include hydrogen (H), carbon (C), and oxygen (O).
Chemical reaction The combination or separation of atoms in which
chemical bonds are formed or broken and new products with dif-
ferent properties are produced.
Chemoreceptor (ke'-mo-re-SEP-tor) Sensory receptor that detects
the presence of a specific chemical.
Chemotaxis (ke-mo-TAK-sis) Attraction of phagocytes to microbes by
a chemical stimulus.
Chiasm (KT-azm) A crossing; especially the crossing of axons in the
optic (II) nerve as they extend toward the opposite optic tract.
Chief cell The secreting cell of a gastric gland that produces pep-
sinogen, the precursor of the enzyme pepsin, and the enzyme
gastric lipase. Also called a zymogenic cell (zT'-mo- JEN-ik). Cell in
the parathyroid glands that secretes parathyroid hormone (PTH).
Also called a principal cell.
Chiropractic (kT-ro-PRAK-tik) A system of treating disease by using
one's hands to manipulate body parts, mostly the vertebral
Cholecystectomy (ko'-le-sis-TEK-to-me) Surgical removal of the
Cholecystitis (ko'-le-sis-TT-tis) Inflammation of the gallbladder.
Cholesterol (ko-LES-te-rol) Classified as a lipid, the most abundant
steroid in animal tissues; located in cell membranes and used for
the synthesis of steroid hormones and bile salts.
Cholinergic neuron (ko'-lin-ER-jik) A neuron that liberates acetylcho-
line as its neurotransmitter.
Chondrocyte (KON-dro-sTt) Cell of mature cartilage.
Chondroitin sulfate (kon-DROY-tin) An amorphous extracellular
matrix material found outside connective tissue cells.
Chordae tendineae (KOR-de TEN-di-ne-e) Tendonlike, fibrous cords
that connect atrioventricular valves of the heart with papillary
Chorion (KO-re-on) The most superficial fetal membrane that
becomes the principal embryonic portion of the placenta; serves
a protective and nutritive function.
Chorionic villi (ko-re-ON-ik VIL-lT) Fingerlike projections of the chorion
that grow into the endometrium and contain fetal blood vessels.
Choroid (KO-royd) One of the vascular coats of the eyeball.
Choroid plexus (PLEK-sus) A network of capillaries located in the roof
of each of the four ventricles of the brain; ependymal cells around
choroid plexuses produce cerebrospinal fluid.
Chromatid (KRO-ma-tid) One of a pair of identical connected nucleo-
protein strands that are joined at the centromere and separate
during cell division, each becoming a chromosome of one of the
two resulting cells.
Chromatin (KRO-ma-tin) The threadlike mass of genetic material, con-
sisting of DNA and histone proteins, that is present in the nucleus
of a nondividing or interphase cell.
Chromatolysis (kro-ma-TOL-i-sis) The breakdown of Nissl bodies into
finely granular masses in the cell body of a neuron whose axon
has been damaged.
Chromosome (KRO-mo-som) One of the small, threadlike structures
in the nucleus of a cell, normally 46 in a human diploid cell, that
bears the genetic material; composed of DNA and proteins (his-
tones) that form a delicate chromatin thread during interphase;
becomes packaged into compact rodlike structures that are vis-
ible under the light microscope during cell division.
Chronic (KRON-ik) Long term or frequently recurring; applied to a
disease that is not acute.
Chronic obstructive pulmonary disease (COPD) A disease, such
as bronchitis or emphysema, in which there is some degree
of obstruction of airways and consequent increase in airway
Chyle (KTL) The milky-appearing fluid found in the lacteals of the
small intestine after absorption of lipids in food.
Chylomicron (kT-lo-MT-kron) Protein-coated sphericalstructure that
contains triglycerides, phospholipids, and cholesterol and is
absorbed into the lacteal of a villus in the small intestine.
Chyme (KTM) The semifluid mixture of partly digested food and
digestive secretions found in the stomach and small intestine dur-
ing digestion of a meal.
Ciliary body (SIL-e-ar'-e) One of the three parts of the vascular tunic
of the eyeball, the others being the choroid and the iris; includes
the ciliary muscle and the ciliary processes.
Cilium (SIL-e-um) A hair or hairlike process projecting from a cell that
may be used to move the entire cell or to move substances along
the surface of the cell.
P lu r a l is
Circadian rhythm (ser-KA-de-an) A cycle of active and nonactive
periods in organisms determined by internal mechanisms and
repeating about every 24 hours.
Circular folds Permanent, deep, transverse folds in the mucosa
and submucosa of the small intestine that increase the surface
area for absorption. Also called plicae circulares (PLT-ke SER-
Circulation time Time required for blood to pass from the right
atrium, through pulmonary circulation, back to the left ventricle,
through systemic circulation to the foot, and back again to the
right atrium; normally about 1