Biology of Disease

Ototoxicity The loss of hearing or balance, tinnitus or

dizziness caused by drug or chemical damage to the

inner ear.

Overhydrated The accumulation of water in body com-

partments (compare withdehydrated).

Pacemaker SeeSinoatrial orSA node.

Palpitations Abnormal or irregular heartbeats of such

severity that the patient is conscious of them.

Pandemic A disease epidemic that affects patients over a

wide geographical area.

Papules These are solid, limited, raised areas of skin about

5 mm in diameter whose shape and color may vary.

Paraparesis A progressive weakness of the legs.

Parasite An organism that lives at the expense of another:

often applied to viruses, protozoa and helminths.

The terms pathogen and parasite are virtually

interchangeable.

Paresthesia Abnormal sensations such as itching, prick-

ling, pins and needles anywhere in the body.

Pathogens These are organisms that cause disease.See

parasite.

Penicillin An antibiotic first discovered (in the mold

Penicillium notatum) in 1928 but only used clinically

since 1940.

Pericarditis An inflammation of the pericardium; can be

acuteorchronic.

Peristalsis The rhythmic waves of smooth muscle con-

tractions that propel food along the gastrointestinal

tract.

Peritoneum The strong, transparent membrane with a

smooth surface that lines the abdomen and binds the

gastrointestinal tract and accessory organs to each

other and to the inner wall of the abdomen.

Petechial hemorrhages These are small, round, dark red

spots caused by bleedings under the skin.

Pharmacology The study of the effects of drugs in the pre-

vention, diagnosis, and treatment or cure of disease.

Phenotype The visible or measurable characteristics of

an individual, or indeed, any observable biological

trait (contrast withgenotype).

Photoaging The characteristic fine and coarse wrinkling,

blotchy pigmentation and rough skin texture induced

by the ultraviolet light from the sun that is a major

factor contributing to the premature aging of skin.

Phototherapy The use of light in treating clinical condi-

tions, for example the repeated exposure for 36 h of

full spectrum bright light to treatseasonally affective

disorder.

Plague A term originally applied to any widespread

disease causing great mortality but now confined to

bubonic plague, an infectious disease of animals and

humans caused by the bacteriumYersinia pestis.

Plasma The protein-rich fluid remaining whenerythro-

cytes,leukocytesandplateletshave been removed

from blood, but with an intact clotting system (see

serum).

Plasma cells Antibody-secreting cells that develop from

B lymphocytes under the influence of cytokines

released fromTHcells.

Plasmapheresis The collection of plasma, with the return

of theerythrocytesandleukocytesto the blood donor

(seeapheresis, leukopheresisandplateletpheresis).

Platelet aggregation This occurs upon wounding when

plateletsextend pseudopodia and become sticky and

clump together when stimulated by ADP to form a

plug that prevents further blood loss.

Plateletpheresis The collection ofplateletsfrom blood

with all other components being returned to the

blood donor (see apheresis, leukopheresis and

plasmapheresis).

Platelets Vesicle-like, subcellular fragments about 3 μm

in diameter with a volume of 7 fdm^3 (femtodecime-

ters^3 or femtoliters) formed by the fragmentation of

megakaryocytes.

Polyallelic The occurrence of many differentallelesof

a gene, although any one individual can only posses

a maximum of two alleles at each locus, given that

chromosomes occur in pairs.

Polyclonal antibodies Each mature, differentiated B lym-

phocyte orplasma cellproduces a single type of anti-

body. However, the response of the immune system

to a singleimmunogenyields hundreds of different

clones of B cells so that the response of the system is

polyclonal, resulting in the appearance of a heteroge-

neous array ofantibodiesin the blood. Compare with

monoclonal antibody.

Polydipsia Intense thirst.

Polymerase chain reaction An experimental, in vitro

method for duplicating in an exponential way short

strands of specific DNA fragments.

Polymorphonuclear leukocyte One of the two main

types ofleukocytesthat can be distinguished from

the other type (mononuclear leukocytes) in having

lobed nuclei and granular cytoplasm.

Polymorphonucleocyte See polymorphonuclear leuko-

cyte.

GLOSSARY

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