exotoxinA poison released by certain
types of bacteriathat 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 drugsand an antitoxin. (See
also endotoxin; enterotoxin.)
exotropiaA term for a divergent squint.
expectorantsCough remediesthat en-
courage the coughing up of sputum.
expectorationThe coughing up and
spitting out of sputum.
exploratory surgeryAny 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.
exposureA 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 milkA technique used by
breast-feedingwomen 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 pump.
exstrophy of the bladderA rare birth
defectin which the bladderis 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, dentalRemoval of teethby
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 haemorrhageBleeding 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 scanningor MRIconfirms the diag-
nosis. Surgical treatment consists of
craniotomy, draining the blood clot, and
clipping the ruptured blood vessel.
extrapyramidal systemA network of
nervepathways 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.EXOTOXIN EXTRAPYRAMIDAL SYSTEME