EXOTOXIN
EXTRAPYRAMIDAL SYSTEM
E
exotoxin
A poison released by certain
types of
bacteria
that enters the blood-
stream and causes widespread effects
around the body. Exotoxins are among
the most poisonous substances known.
Infections by
tetanus
,
diphtheria
,
and
some other bacteria that release life-
threatening exotoxins can be prevented
by
immunization
.
Treatment of such in-
fections usually includes administration
of
antibiotic drugs
and an
antitoxin
.
(See
also
endotoxin
;
enterotoxin
.)
exotropia
A term for a divergent
squint
.
expectorants
Cough remedies
that en-
courage the coughing up of
sputum
.
expectoration
The
coughing
up and
spitting out of
sputum
.
exploratory
surgery
Any operation
that is carried out to investigate or ex-
amine part of the body to discover the
extent of known disease or to establish
a diagnosis. Advances in imaging tech-
niques, such as
MRI
, have reduced the
need for exploratory surgery.
exposure
A term used to describe the
effects on the body of being subjected
to very low temperatures, or to a combi-
nation of low temperatures, wetness,
and high winds. The primary danger in
these conditions is
hypothermia
.
The term is also used to describe sub-
jection to radiation or pollutants.
expressing milk
A technique used by
breast-feeding
women for removing milk
from the breasts. It may be needed if
the woman's breasts are overfull (see
engorgement
). A woman may want to
express milk so that it can be given to
the baby in her absence, or so that an
infant unable to feed at the breast, due
to prematurity, for example, can benefit
from breast milk. Milk can be expressed
by hand or with a
breast pum p
.
exstrophy of the bladder
A rare
birth
defect
in which the
bladder
is turned
inside out and is open to the outside of
the body through a space in the lower
abdominal wall. Usually, there are also
other defects, such as
epispadias
in
males and failure of the pubic bones to
join at the front. Surgical treatment
involves reconstructing the bladder and
closing the abdominal wall. If the blad-
der is very small, it is removed and the
urine diverted (see
urinary diversion
).
extraction, dental
Removal of
teeth
by
a dentist. Extraction may be performed
when a tooth is severely decayed or too
badly broken to be repaired, or when
an abscess (see
abscess, dental
) has
formed. Teeth may also be removed if
there is crowding or
malocclusion
, if the
teeth are loose due to gum disease, or
if they are preventing another tooth
from erupting (see
eruption of teeth
).
For most extractions, local anaesthe-
sia is used (see
anaesthesia, dental
).
Teeth are usually extracted with dental
forceps, which grasp the root of the
tooth. In difficult extractions, some gum
and bone may also need to be removed
from around the tooth.
extradural haemorrhage
Bleeding in-
to the space between the inner surface
of the skull and the external surface of
the
dura mater
, the outer layer of the
meninges
. Extradural haemorrhage usu-
ally results from a blow to the side of
the head that fractures the skull and
ruptures an artery running over the sur-
face of the dura mater. A
haematoma
(collection of clotted blood) forms and
enlarges, causing an increase in pres-
sure inside the skull and resulting in
symptoms several hours or even days
after the injury. Symptoms may include
headache, drowsiness, vomiting, paraly-
sis affecting one side of the body, and
seizures
. Untreated, extradural haemor-
rhage may be life-threatening.
CT scanning
or
MRI
confirms the diag-
nosis. Surgical treatment consists of
craniotomy
, draining the blood clot, and
clipping the ruptured blood vessel.
extrapyramidal system
A network of
nerve
pathways that links nerve nuclei
in the surface of the
cerebrum
, the
basal
ganglia
, and parts of the
brainstem
. The
system influences and modifies electri-
cal impulses sent from the brain to
initiate movement in skeletal muscles.
Damage or degeneration of compo-
nents in the extrapyramidal system
can disrupt the execution of voluntary
movements and can produce involun-
tary tremors or jerks. Such disturbances
are seen in
Huntington's disease
,
Parkin-
son's disease
,
some types of
cerebral
palsy
, and can also occur as a side-
effect of
phenothiazine drugs
.
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