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Glossary
Dermatome
The area of the skin supplied with afferent
nerve fibers of a single dorsal root of a spinal nerve.
Desmosome
A small, circular, dense area within the
intercellular bridge that forms the site of adhesion
between intermediate filaments and cell membranes.
Desquamation
A normal process in which the cornified
layer of the epidermis is shed in fine scales or sheets.
Dialysis
The process of separating colloids and crystal-
line substances in solution, which involves the two
distinct physical processes of diffusion and ultrafil-
tration; or a medical procedure for the removal of
urea and other elements from the blood or lymph.
Diapedesis
The outward passage of red or white blood
corpuscles through the intact walls of the vessels.
Diaphoresis
Perspiration, especially the profuse perspi-
ration associated with elevated body temperature,
physical exertion, exposure to heat, and mental or
emotional stress.
Diarthrosis
A specialized articulation that permits,
to some extent, free joint movement. (Adjective:
diarthrodial)
Diastole
The dilatation of the heart; or the period of
dilatation, which is the interval between the second
and the first heart sound and is the time during
which blood enters the relaxed chambers of the
heart from the systemic circulation and the lungs.
Differentiation
The act or process in development in
which unspecialized cells or tissues acquire more spe-
cialized characteristics, including those of physical
form, physiologic function, and chemical properties.
Diffusion
The process of becoming widely spread, as
in the spontaneous movement of molecules or other
particles in solution from an area of higher concen-
tration to an area of lower concentration, resulting
in an even distribution of the particles in the fluid.
Dimer
A compound or unit formed by the combination
of two identical molecules or radicals of a simpler
compound. (Adjective: dimeric)
Diopter
A unit of measurement of the refractive power
of lenses equal to the reciprocal of the focal length
in meters.
Diploid
Pertaining to an individual, organism,
strain, or cell that has two full sets of homologous
chromosomes.
Disseminate
To scatter or distribute over a consider-
able area.
Distal
Away from or being the farthest from a point of
reference.
Diurnal
Of, relating to, or occurring in the daytime.
Diverticulum
A pouch or sac of variable size occurring
naturally or through herniation of the muscular wall
of a tubular organ.
Dorsum
The back or posterior. (Adjective: dorsal)
Dysgenesis
Defective or abnormal development of an
organ or part, typically occurring during embryonic
development. (Also called dysgenesia.)
Dyslexia
A disturbance in the ability to read, spell, and
write words.
Dyspepsia
The impairment of the power or function of
digestion, especially epigastric discomfort following
eating.
Dysphagia
A difficulty in swallowing.
Dysphonia
Any impairment of the voice that is experi-
enced as difficulty in speaking.
Dysplasia
The alteration in size, shape, and organization
of adult cell types.
Eburnation
The conversion of bone or cartilage,
through thinning or loss, into a hard and dense mass
with a worn, polished, ivorylike surface.
Ecchymosis
A small hemorrhagic spot, larger than a pete-
chia, in the skin or mucous membrane caused by the
extravasation of blood into the subcutaneous tissues.
Ectoderm
The outermost of the three primary germ
layers of the embryo, and from which the epidermis
and epidermal tissues, such as nails, hair, and glands
of the skin, develop.
Ectopic
Relating to or characterized by an object or
organ being situated in an unusual place, away from
its normal location.
Edema
The presence of an abnormal accumulation
of fluid in interstitial spaces of tissues. (Adjective:
edematous)
Efferent
Conveyed or directed away from a center.
Effusion
The escape of fluid from blood vessels into a
part or tissue, as an exudation or a transudation.
Embolus
A mass of clotted blood or other formed ele-
ments, such as bubbles of air, calcium fragments, or
a bit of tissue or tumor, that circulates in the blood-
stream until it becomes lodged in a vessel, obstruct-
ing the circulation. (Plural: emboli)
Empyema
An accumulation of pus in a cavity of the
body, especially the pleural space.
Emulsify
To disperse one liquid throughout the body
of another liquid, making a colloidal suspension, or
emulsion.
Endocytosis
The uptake or incorporation of substances
into a cell by invagination of its plasma membrane,
as in the processes of phagocytosis and pinocytosis.
Endoderm
The innermost of the three primary germ lay-
ers of the embryo, and from which epithelium arises.
Endogenous
Growing within the body; or developing
or originating from within the body or produced
from internal causes.
Endoscopy
The visualization of any cavity of the body
with an endoscope.
Enteral
Within or pertaining to the intestine.
Enteropathic
Relating to any disease of the intestinal
tract.
Enzyme
A protein molecule produced by living cells
that catalyzes chemical reactions of other organic
substances without itself being destroyed or altered.
Epiphysis
The expanded articular end of a long bone
(head) that is separated from the shaft of the bone
by the epiphyseal plate until the bone stops growing,
the plate is obliterated, and the shaft and the head
become united.
Epithelium
The covering of the internal and external
surfaces of the body, including the lining of vessels
and other small cavities.
Epitope
The simplest form of an antigenic determinant
that combines with an antibody or a T-cell receptor
to cause a specific reaction by an immunoglobulin.
