EPHEDRINE
E
ephedrine
A drug that mimics the effects of the
neurotransmitter
noradrenaline
(norep-
inephrine). Ephedrine is prescribed as a
decongestant drug
to treat nasal conges-
tion. It may also be used to treat some
cases of low blood pressure that are due
to drug actions or disease.
epicanthic fold
A vertical fold of skin extending from
the upper eyelid to the side of the nose.
Epicanthic folds are common in East
Asian people but rare in other races,
except in babies, in whom they usually
disappear as the nose develops. Abnor-
mal epicanthic folds are a feature of
Down’s syndrome
.
If desired, the folds can
be removed by cosmetic surgery.
epicardium
The outermost of the three layers that
form the wall of the
heart
.
The epicar-
dium is a smooth membranous structure
that envelops the
myocardium
(the mus-
cle layer of the heart).
epicondyle
Any bony outgrowth to w hich
tendons
are attached (for example, at the lower
end of the
humerus
(upper-arm bone)
where it forms part of the
elbow
joint).
Overuse of muscles, leading to repeated
tugging on the tendons, can result in
pain and inflammation at an epicondyle
(see
epicondylitis
) .
epicondylitis
Painful inflammation of an
epicondyle,
and specifically one of the bony prom i-
nences of the
elbow
at the lower end of
the humerus
(upper-arm bone). Epi-
condylitis is the result of overuse of the
forearm muscles, w hich causes repeated
tugging on the tendons at their point of
attachment to the bone.
Epicondylitis that affects the prom i-
nence on the outer elbow is called
tennis
elbow
.
When the prominence on the
inner elbow is affected the condition is
called
golfer’s elbow
.
epidemic
A term applied to a disease that for the
majority of the time is rare in a commu-
nity but that suddenly spreads rapidly to
affect a large number of people.
Epidemics of new strains of
influenza
are
common,
occurring
periodically
when the influenza virus changes to a
form to w hich the population has no
resistance. (See also
endemic
. )
epidemiology
The branch of medicine that is con-
cerned with the occurrence and distri-
bution of disease, including
infectious
diseases
(such as cholera or influenza)
and noninfectious
diseases
(such
as
cancer and heart disease).
In epidemiological studies, the mem-
bers of a population are counted and
described in terms of such variables as
race, sex, age, social class, and occupa-
tion. The
incidence
and
prevalence
of the
disease of interest are then determined.
These observations may be repeated at
regular
intervals
in
order
to
detect
changes over time. The result is a stat-
istical
record
that
may
reveal
links
between particular variables and distrib-
ution 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 can-
cer in each group is calculated. In such
cases, the epidemiologist is careful to
make the two groups as identical as
possible in all other relevant respects,
and w ill carefully match factors such as
age, sex, and weight.
epidermis
The thin outermost layer of the
skin.
epidermoid cyst
A harmless nodule under the skin’s sur-
face that contains yellow, cheesy material.
The terms epidermoid cyst and
sebaceous
cyst
are often used interchangeably.
epidermolysis bullosa
A group of rare, inherited conditions,
varying widely in severity, in w hich
blisters appear on the skin after minor
injury or occur spontaneously.
CAUSES
Epidermolysis bullosa is caused by a
genetic defect that may show either an
autosomal dominant or an autosomal
recessive
pattern
of inheritance
(see
genetic disorders).
DIAGNOSIS AND
TREATMENT
The conditions can be diagnosed by
means of a skin
biopsy
(the removal
of a small sample of tissue for m icro-
scopic analysis).
There is no specific treatment for the
condition, but injury to the skin should
be
avoided and
protective
measures
should be taken to prevent the rubbing
of affected areas when blisters appear.
The outlook varies from gradual im -
provement in m ild cases to progressive
disease in the most severe cases.
epididymal cyst
A harmless, usually painless, swelling in
the
epididymis
(the coiled tube at the
back of the testis). Small cysts are fairly
common in men over the age of 40 and
need no treatment. Rarely, they enlarge
or become tender, causing discomfort.
In such cases, it may be necessary for
the cysts to be surgically removed.
epididymis
A 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 that leads to the urethra). Sperm
cells, which are produced in the testis,
mature as they pass slowly along the
epididymis, until they are capable of fer-
tilizing an egg, and they are then stored
until
ejaculation
takes place.
Disorders of the epididymis include
epididymal cysts
(fluid-filled swellings in
the epididymis) and
epididymo-orchitis
(inflammation of the testis and epi-
didymis). Infection or injury can block
the
epididymis;
if
both
testes
are
affected,
infertility
may result.
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