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Abduction
The act of abducting (moving or spreading
away from a position near the midline of the body
or the axial line of a limb) or the state of being
abducted.
Abrasion
The wearing or scraping away of a substance
or structure, such as the skin, through an unusual or
abnormal mechanical process.
Abscess
A collection of pus that is restricted to a
specific area in tissues, organs, or confined spaces.
Accommodation
The adjustment of the lens (eye) to
variations in distance.
Acromion
The lateral extension of the spine of the
scapula, forming the highest point of the shoulder.
(Adjective: acromial)
Acuity
The clearness or sharpness of perception, espe-
cially of vision.
Adaptation
The adjustment of an organism to its
physical or psychological environment, through
changes and responses to stress of any kind.
Adduction
The act of adducting (moving or drawing
toward a position near the midline of the body
or the axial line of a limb) or the state of being
adducted.
Adhesin
The molecular components of the bacterial
cell wall that are involved in the adhesion processes.
Adrenergic
Activated by or characteristic of the sym-
pathetic nervous system or its neurotransmitters
(i.e., epinephrine and norepinephrine).
Aerobic
Growing, living, or occurring only in the pres-
ence of air or oxygen.
Afferent
Bearing or conducting inward or toward a
center, as an afferent neuron.
Agglutination
The clumping together of particles,
microorganisms, or blood cells in response to an
antigen–antibody reaction.
Agonist
A muscle whose action is opposed by another
muscle (antagonist) with which it is paired or a drug
or other chemical substance that has affinity for or
stimulates a predictable physiologic function.
Akinesia
An abnormal state in which there is an
absence or poverty of movement.
Allele
One of two or more different forms of a gene
that can occupy a particular locus on a chromosome.
Alveolus
A small saclike structure, as in the alveolus of
the lung.
Ambient
The surrounding, encompassing, or prevailing
area or environment; especially of or pertaining to
the area immediately around the body.
Amblyopia
A condition of vision impairment without
a detectable organic lesion of the eye.
Amine
An organic compound containing nitrogen.
Amorphous
Without a definite form; shapeless.
Amphoteric
Capable of reacting chemically as an acid
or a base.
Ampulla
A saclike dilatation of a duct, canal, or any
other tubular structure.
Anabolism
A constructive metabolic process charac-
terized by the conversion of simple substances into
larger, complex molecules.
Anaerobic
Growing, living, or occurring only in the
absence of air or oxygen.
Analog
A part, organ, or chemical having the same
function or appearance but differing in respect to a
certain component, such as origin or development.
Anaplasia
A change in the structure of cells and in their
orientation to each other that is characterized by a
loss of cell differentiation, as in cancerous cell growth.
Anastomosis
The connection or joining between two
vessels; or an opening created by surgical, traumatic,
or pathologic means.
Androgen
Any substance, such as a male sex hormone,
that increases male characteristics.
Anergy
A state of absent or diminished reaction to an
antigen or group of antigens.
Aneuploidy
A variation in the number of chromo-
somes within a cell involving one or more missing
chromosomes rather than entire sets.
Aneurysm
An outpouching or dilation in the wall of a
blood vessel or the heart.
Ankylosis
Stiffness or fixation of separate bones of
a joint, resulting from disease, injury, or surgical
procedure. (Verb: ankylose)
Anorexia
Lack or loss of appetite for food. (Adjective:
anorexic)
Anoxia
An abnormal condition characterized by the
total lack of oxygen.
Antagonist
A muscle whose action directly opposes
that of another muscle (agonist) with which it is
paired, or a drug or other chemical substance that
can diminish or nullify the action of a neuromediator
or body function.
Anterior
Pertaining to a surface or part that is situated
near or toward the front.
Antigen
A substance that generates an immune
response by causing the formation of an antibody or
reacting with antibodies or T-cell receptors.
Apex
The uppermost point, the narrowed or pointed
end, or the highest point of a structure, such as an
organ.
Aphagia
A condition characterized by the refusal or
the loss of ability to swallow.
Aplasia
The absence of an organ or tissue due to a
developmental failure.
Apnea
The absence of spontaneous respiration.
Apoptosis
A mechanism of programmed cell death,
marked by shrinkage of the cell, condensation of
chromatin, formation of cytoplasmic blebs, and
fragmentation of the cell into membrane-bound
bodies eliminated by phagocytosis.
Apraxia
Loss of the ability to carry out familiar, pur-
poseful acts or to manipulate objects in the absence
of paralysis or other motor or sensory impairment.
G l o s s a r y
