Deep fascia (FASH-e-a) A sheet of connective tissue wrapped around
a muscle to hold it in place.
Defecation (def-e-KA-shun) The discharge of feces from the rectum.
Deglutition (de-gloo-TISH-un) The act of swallowing.
Dehydration (de-hT-DRA-shun) Excessive loss of water from the body
or its parts.
Demineralization (de-min'-er-al-i-ZA-shun) Loss of calcium and phos-
phorus from bones.
Denaturation (de-na-chur-A-shun) Disruption of the tertiary structure
of a protein by heat, changes in pH, or other physical or chemical
methods, in which the protein loses its physical properties and
Dendrite (DEN-drTt) A neuronal process that carries electrical signals
toward the cell body.
Dendritic cell (den-DRIT-ik) One type of antigen-presenting cell with
long branchlike projections that commonly is present in mucosal
linings such as the vagina, in the skin (Langerhans cells in the
epidermis), and in lymph nodes.
Dental caries (KA-rez) Gradual demineralization of the enamel and
dentin of a tooth that may invade the pulp and alveolar bone.
Also called tooth decay.
Dentin (DEN-tin) The bony tissues of a tooth enclosing the pulp cavity.
Dentition (den-TI-shun) The eruption of teeth. The number, shape,
and arrangement of teeth.
Deoxyribonucleic acid (DNA) (de-ok'-se-rT'-bo-noo-KLE-ik) A nucleic
acid constructed of nucleotides consisting of one of four bases
(adenine, cytosine, guanine, or thymine), deoxyribose, and a phos-
phate group; encoded in the nucleotides is genetic information.
Depolarization (de-po-lar-i-ZA-shun) A reduction of voltage across a
plasma meembrane; expressed as a change toward less nega-
tive (more positive) voltages on the interior surface of the plasma
Depression (de-PRESH-un) Movement in which a part of the body
Dermal papilla (pa-PILL-a) Fingerlike projection of the papillary
region of the dermis that may contain blood capillaries or cor-
puscles of touch (Meissner corpuscles).
Dermatology (der-ma-TOL-o-je) The medical specialty dealing with
diseases of the skin.
Dermatome (DER-ma-tom) The cutaneous area developed from one
embryonic spinal cord segment and receiving most of its sensory
innervation from one spinal nerve. An instrument for incising the
skin or cutting thin transplants of skin.
Dermis (DER-mis) A layer of dense irregular connective tissue lying
deep to the epidermis.
Descending colon (KO-lon) The part of the large intestine descend-
ing from the left colic (splenic) flexure to the level of the left iliac
Detritus (de-TRT-tus) Particulate matter produced by or remaining
after the wearing away or disintegration of a substance or tissue;
scales, crusts, or loosened skin.
Detrusor muscle (de-TROO-ser) Smooth muscle that forms the wall
of the urinary bladder.
Developmental biology The study of development from the fertilized
egg to the adult form.
Diagnosis (dT-ag-NO-sis) Distinguishing one disease from another or
determining the nature of a disease from signs and symptoms by
inspection, palpation, laboratory tests, and other means.
Dialysis (dT-AL-i-sis) The removal of waste products from blood by
diffusion through a selectively permeable membrane.
Diaphragm (DT-a-fram) Any partition that separates one area from
another, especially the dome-shaped skeletal muscle between
the thoracic and abdominal cavities. Also a dome-shaped device
that is placed over the cervix, usually with a spermicide, to pre-
Diaphysis (dT-AF-i-sis) The shaft of a long bone.
Diarrhea (dT-a-RE-a) Frequent defecation of liquid feces caused by
increased motility of the intestines.
Diarthrosis (dT-ar-THRO-sis) A freely movable joint; types are gliding,
hinge, pivot, condyloid, saddle, and ball-and-socket.
Diastole (dT-AS-to-le) In the cardiac cycle, the phase of relaxation or
dilation of the heart muscle, especially of the ventricles.
Diastolic blood pressure (dT-as-TOL-ik) The force exerted by blood on
arterial walls during ventricular relaxation; the lowest blood pres-
sure measured in the large arteries, normally about 70 mmHg in
a young adult.
Diencephalon (dT'-en-SEF-a-lon) A part of the brain consisting of the
thalamus, hypothalamus, epithalamus, and subthalamus.
Diffusion (dif-0-zhun) A passive process in which there is a net or
greater movement of molecules or ions from a region of high
concentration to a region of low concentration until equilibrium
Digestion (dT-JES-chun) The mechanical and chemical breakdown of
food to simple molecules that can be absorbed and used by body
Dilate (DI-lat) To expand or swell.
Diploid (DIP-loyd) Having the number of chromosomes character-
istically found in the somatic cells of an organism; having two
haploid sets of chromosomes, one each from the mother and
2 n .
Direct motor pathways Collections of upper motor neurons with
cell bodies in the motor cortex that project axons into the spinal
cord, where they synapse with lower motor neurons or interneu-
rons in the anterior horns. Also called the pyramidal pathways
Disease Any change from a state of health.
Dislocation (dis-lo-KA-shun) Displacement of a bone from a joint with
tearing of ligaments, tendons, and articular capsules. Also called
Dissect (di-SEKT) To separate tissues and parts of a cadaver or an
organ for anatomical study.
Distal (DIS-tal) Farther from the attachment of a limb to the trunk;
farther from the point of origin or attachment.
Diuretic (dT-u-RET-ik) A chemical that increases urine volume by
decreasing reabsorption of water, usually by inhibiting sodium