1190
Glossary
Glycolysis
A series of enzymatically catalyzed reac-
tions, occurring within cells, by which glucose is
converted to adenosine triphosphate (ATP) and
pyruvic acid during aerobic metabolism.
Gonad
A gamete-producing gland, as an ovary or a testis.
Gradient
The rate of increase or decrease of a measur-
able phenomenon expressed as a function of a sec-
ond; or the visual representation of such a change.
Granuloma
A small mass of nodular granulation tissue
resulting from chronic inflammation, injury, or
infection. (Adjective: granulomatous)
Hapten
A small, nonproteinaceous substance that is
not antigenic by itself but that can act as an antigen
when combined with a larger molecule.
Haustrum
A structure resembling a recess or saccula-
tion. (Plural: haustra)
Hematoma
A localized collection of extravasated
blood trapped in an organ, space, or tissue, resulting
from a break in the wall of a blood vessel.
Hematopoiesis
The normal formation and development
of blood cells.
Hemianopia
Defective vision or blindness in half of the
visual field of one or both eyes.
Heterogeneous
Consisting of or composed of dissimilar
elements or parts; or not having a uniform quality
throughout. (Noun: heterogeneity)
Heterophagy
The taking into the cell of an exogenous
substance by phagocytosis or pinocytosis and the
subsequent digestion of the newly formed vacuole
by a lysosome.
Heterozygous
Having two different alleles at corre-
sponding loci on homologous chromosomes.
Histology
The branch of anatomy that deals with the
minute (microscopic) structure, composition, and
function of cells and tissue. (Adjective: histologic)
Homolog
Any organ or part corresponding in function,
position, origin, and structure to another organ or
part, as the flippers of a seal correspond to human
hands. (Adjective: homologous)
Homozygous
Having two identical alleles at corre-
sponding loci on homologous chromosomes.
Humoral
Relating to elements dissolved in the blood
or body fluids.
Hybridoma
A tumor of hybrid cells produced by
fusion of normal lymphocytes and tumor cells.
Hydrolysis
The chemical alteration or decomposition
of a compound into fragments by the addition of
water.
Hypercapnia
Excess amounts of carbon dioxide in the
blood.
Hyperemia
An excess or engorgement of blood in a
part of the body.
Hyperesthesia
An unusual or pathologic increase in
sensitivity of a part, especially the skin, or of a
particular sense.
Hyperplasia
An abnormal multiplication or increase in
the number of normal cells of a body part.
Hypertonic
A solution having a greater concentra-
tion of solute than another solution with which it
is compared, hence exerting more osmotic pressure
than that solution.
Hypertrophy
The enlargement or overgrowth of an
organ that is due to an increase in the size of its cells
rather than the number of its cells.
Hypesthesia
An abnormal decrease of sensation in
response to stimulation of the sensory nerves. (Also
called hypoesthesia.)
Hypocapnia
A deficiency of carbon dioxide in the
blood.
Hypotonic
A solution having a lesser concentration of
solute than another solution with which it is com-
pared, hence exerting less osmotic pressure than that
solution.
Hypoxia
An inadequate supply of oxygen to tissue
that is below physiologic levels despite adequate
perfusion of the tissue by blood.
Iatrogenic
Induced inadvertently through the activity
of a physician or by medical treatment or diagnostic
procedures.
Idiopathic
Arising spontaneously or from an unknown
cause.
Idiosyncrasy
A physical or behavioral characteristic
or manner that is unique to an individual or group.
(Adjective: idiosyncratic)
Immunogenicity
The property that provides a substance
with the capacity to produce an immune response.
(Adjective: immunogenic)
Incidence
The rate at which a certain event occurs
(e.g., the number of new cases of a specific disease
during a particular period of time in a population at
risk).
Inclusion
The act of enclosing or the condition of
being enclosed; or anything that is enclosed.
Indigenous
Native, or natural, to a particular country
or region.
Infarction
Necrosis or death of tissues due to local
ischemia resulting from obstruction of blood flow.
Inotropic
Influencing the force or energy of muscular
contractions.
In situ
In the natural or normal place; or something,
such as cancer, that is confined to its place of origin
and has not invaded neighboring tissues.
Interferon
Any one of a group of small glycoproteins
(cytokines) produced in response to viral infection
and which inhibit viral replication.
Interleukin
Any of several multifunctional cytokines
produced by a variety of lymphoid and nonlym-
phoid cells, including immune cells, that stimulate or
otherwise affect the function of lymphopoietic and
other cells and systems in the body.
Interstitial
Relating to or situated between parts or in
the interspaces of a tissue.
Intramural
Situated or occurring within the wall of an
organ.
Intrinsic
Pertaining exclusively to a part or situated
entirely within an organ or tissue.
In vitro
A biologic reaction occurring in an artificial
environment, such as a test tube.
In vivo
A biologic reaction occurring within the living
body.
Involution
The act or instance of enfolding, entangling,
or turning inward.
