Bma Illustrated Medical Dictionary

duced in the testis, mature as they pass

slowly along the epididymis and are

then stored in the seminal vesiclesuntil

ejaculationtakes place.

Disorders of the epididymis include

epididymo-orchitisand epididymal cysts.

Infection or injury can block the epidi-

dymis, which, if both testes are affected,

may result in infertility.

epididymitisSee epididymo-orchitis.

epididymo-orchitisAcute inflamma-

tion of a testisalong with its associated

epididymis. Epididymo-orchitis causes

severe pain and swelling at the back of

the testis, and, in severe cases, swelling

and redness of the scrotum.

The inflammation is caused by infec-

tion. Often, there is no obvious source

of infection, but sometimes the cause is

a bacterial urinary tract infectionthat

has spread via the vas deferensto the

epididymis. Treatment is with antibiotic

drugs. If there is an underlying urinary

tract infection, its cause will be investi-

gated. (See also orchitis.)

epidural anaesthesiaA method of

pain relief in which a local anaesthetic

(see anaesthetic, local) is injected into

the epidural space (the space around

the membranes surrounding the spinal

cord) in the middle and lower back to

numb the nerves that supply the chest

and lower body. Epidural anaesthesia is

used to relieve pain during and after

surgery and during childbirth.

epiglottisThe flap of cartilagelying

behind the tongue and in front of the

epidemicA term applied to a disease
that for most of the time is rare in a
community but suddenly spreads rapid-
ly to affect a large number of people.
Epidemics of new strains of influenza
are common. (See also endemic.)
epidemiologyThe branch of medicine
concerned with the occurrence and dis-
tribution of disease, including infectious
diseases and noninfectious diseases
such as cancer.
In epidemiological studies, the mem-
bers of a population are counted and
described in terms of such variables as
race, sex, age, social class, occupation,
and marital status. Then the incidence
and prevalenceof the disease of inter-
est are determined. These observations
may be repeated at regular intervals in
order to detect changes over time. The
result is a statistical record that may
reveal links between particular variables
and distribution of disease.
In comparative epidemiological stud-
ies, two or more groups are chosen. For
example, in a study of the link between
smoking and lung cancer, one group
may consist of smokers and the other of
nonsmokers; the proportion with cancer
in each group is calculated.
epidermisThe thin outermost layer of
the skin.
epidermolysis bullosaA group of
rare, inherited conditions, varying wide-
ly in severity, in which blisters appear
on the skin after minor injury or occur
spontaneously. The conditions can be
diagnosed by a skin biopsy. There is no
specific treatment. The outlook varies
from gradual improvement in mild
cases to progressive serious disease in
the most severe cases.
epididymal cystA harmless swelling,
usually painless, that develops in the
epididymis. Small cysts are common in
men over 40 and need no treatment.
Rarely, they become tender or enlarge
and cause discomfort, in which case
surgical removal may be necessary.
epididymisA long, coiled tube that
runs along the back of the testis and
connects the vasa efferentia (small
tubes leading from the testis) to the vas
deferens(the sperm duct leading to the
urethra). Sperm cells, which are pro-

EPIDEMIC EPIGLOTTITIS

E

Urethra

Seminal

vesicle

Bladder

Vas

deferens

EPIDIDYMIS

Penis

Testis

Epididymis

Ureter