Glossary
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Phagocytosis
The process by which certain cells engulf
and consume foreign material and cell debris.
Phalanx
Any one of the bones composing the fingers of
each hand and the toes of each foot.
Phenotype
The complete physical, biochemical, and
physiologic makeup of an individual, as determined
by the interaction of both genetic makeup and envi-
ronmental factors.
Pheresis
A procedure in which blood is withdrawn
from a donor, a portion (plasma, leukocytes, etc.) is
separated and retained, and the remainder is reper-
fused into the donor. It includes plasmapheresis and
leukophoresis.
Pili
Hair; or in microbiology, the minute filamentous
appendages of certain bacteria. (Singular: pilus)
Plethora
A body condition characterized by an excess
of any of the body fluids, especially blood, marked
by distention and a beefy red coloration. (Adjective:
plethoric)
Plexus
A network of intersecting nerves, blood vessels,
or lymphatic vessels.
Polygene
Any of a group of nonallelic genes that inter-
act to influence the same character in the same way
so that the effect is cumulative, usually of a quanti-
tative nature, as size, weight, or skin pigmentation.
(Adjective: polygenic)
Polymorph
One of several, or many, forms of an
organism or cell. (Adjective: polymorphic)
Polyp
A small, tumor-like growth that protrudes from
a mucous membrane surface.
Polypeptide
A molecular chain of more than two
amino acids joined by peptide bonds.
Presbyopia
A visual condition (farsightedness) that
commonly develops with advancing years or old age
in which the lens loses elasticity, causing defective
accommodation and inability to focus sharply for
near vision.
Prevalence
The number of new and old cases of a disease
that are present in a population at a given time, or
occurrences of an event during a particular period
of time.
Prodrome
An early symptom indicating the onset of a
condition or disease. (Adjective: prodromal)
Prokaryotic
Pertaining to an organism, such as bacte-
rium, with cells lacking a true nucleus and nuclear
membrane that reproduces through simple fission.
Prolapse
The falling down, sinking, or sliding of an
organ from its normal position or location in the body.
Proliferation
The reproduction or multiplication of
similar forms, especially cells.
Pronation
Assumption of a position in which the ven-
tral, or front, surface of the body or part of the body
faces downward. (Adjective: prone)
Propagation
The act or action of reproduction.
Proprioception
The reception of stimuli originating
from within the body regarding body position and
muscular activity by proprioceptors (sensory nerve
endings found in muscles, tendons, joints).
Prosthesis
An artificial replacement for a missing body
part; or a device designed and applied to improve
function, such as a hearing aid.
Proteoglycans
Any one of a group of polysaccharide-
protein conjugates occurring primarily in the matrix
of connective tissue and cartilage.
Proto-oncogene
A normal cellular gene that with altera-
tion, such as by mutation, becomes an active oncogene.
Proximal
Closer to a point of reference, usually the
trunk of the body, than other parts of the body.
Pruritus
The symptom of itching, an uncomfortable
sensation leading to the urge to rub or scratch the
skin to obtain relief. (Adjective: pruritic)
Purpura
A small hemorrhage, up to about 1 cm in
diameter, in the skin, mucous membrane, or serosal
surface; or any of several bleeding disorders charac-
terized by the presence of purpuric lesions.
Purulent
Producing or containing pus.
Quiescent
Quiet, causing no disturbance, activity, or
symptoms.
Reflux
An abnormal backward or return flow of a
fluid, such as stomach contents, blood, or urine.
Regurgitation
A flow of material that is in the opposite
direction from normal, as in the return of swallowed
food into the mouth or the backward flow of blood
through a defective heart valve.
Remission
The partial or complete disappearance of
the symptoms of a chronic or malignant disease; or
the period of time during which the abatement of
symptoms occurs.
Resorption
The loss of substance or bone by physi-
ologic or pathologic means; for example, the loss of
dentin and cementum of a tooth.
Retrograde
Moving backward or against the usual
direction of flow; reverting to an earlier state or
worse condition (degenerating); catabolic.
Retroversion
A condition in which an entire organ is
tipped backward or in a posterior direction, usually
without flexion or other distortion.
Rhabdomyolysis
Destruction or degeneration of
muscle, associated with myoglobinuria (excretion of
myoglobin in the urine).
Rostral
Situated near a beak (oral or nasal region).
Sacroiliitis
Inflammation in the sacroiliac joint.
Saprophyte
An organism that obtains nourishment
from the products of organic breakdown and decay.
(Adjective: saprophytic)
Sclerosis
A condition characterized by induration or
hardening of tissue resulting from any of several
causes, including inflammation, diseases of the inter-
stitial substance, and increased formation of connec-
tive tissues.
Scotopic vision
Describes vision, especially night
vision, when the eye is dark adapted.
Semipermeable
Partially but not wholly permeable,
especially a membrane that permits the passage of
some (usually small) molecules but not the passage
of other (usually larger) particles.
Senescence
The process or condition of aging or grow-
ing old.
Sepsis
The presence in the blood or other tissues of
pathogenic microorganisms or their toxins; or the
condition resulting from the spread of microorgan-
isms or their products. (Adjective: septic)
