The
injured
arm
may be supported
horizontally or held
elevated, depend-
ing on the injury.
slipped disc See
disc prolapse.
slipped femoral
e p ip h y s is See
femoral
epiphysis,
slipped
.
slit-lamp An illu-
minated
type
of
microscope that is
used to examine
the internal struc-
tures of the front
part of the eye and of the retina at the
back. (See also
eye, examination of.)
slough Dead tissue that has been shed
from its original site; for example, loss
of dead skin cells from the skin's surface.
slow virus diseases A group of dis-
eases of the central nervous system that
occur many months or even years after
infection with a virus. They cause gradual
widespread destruction of nerve tissue,
with progressive loss of brain function
and a fatal outcome. Examples include
Creutzfeldt-Jakob disease
and
kuru.
small
cell
carcinoma One form of
lung cancer.
smallpox A highly infectious viral dis-
ease that was declared eradicated in
1980 after a global vaccination campaign.
smear A
specimen
for
microscopic
examination prepared by spreading a
thin film of cells on to a glass slide.
smegma An accumulation of sebaceous
gland secretions under the foreskin in an
uncircumcised male, usually as a result
of poor hygiene. Fungal or bacterial in-
fection of smegma may cause
balanitis
.
smell One of the 5 senses. In the nose,
hair-like projections from smell receptor
cells lie in the mucous membrane. When
the receptors are stimulated by certain
molecules, they transmit impulses along
the olfactory nerves to the smell centres
in the
limbic system
and frontal lobes of
the brain, where smell is perceived.
Possible causes of loss of the sense
of smell include inflammation of the
nasal membrane, as in a common
cold
;
cigarette
smoking
; hypertrophic
rhinitis
,
SLIPPED DISC
SLING
ELEVATION SLING
in which thickening of the mucous mem-
brane obscures olfactory nerve endings;
atrophic rhinitis, in which the nerves
waste away; head injury that tears the
nerves; or a tumour of the meninges or
nasopharynx. The perception of illusory,
unpleasant odours may be a feature of
depression
,
schizophrenia
, some forms
of
epilepsy,
or alcohol withdrawal.
smelling salts A preparation of
ammo-
nia
that was used in the past to revive a
person who felt faint.
smoking Smoking
tobacco
in the form of
cigarettes or cigars, or in pipes. Over
100,000
deaths per year in the UK are
attributed to smoking. The main harm-
ful effects of smoking are
lung cancer,
bronchitis
,
emphysema
,
coronary artery
disease,
and
peripheral vascular disease.
Smoking also increases the risk of
mouth cancer
,
lip cancer
, and throat
cancer (see
pharynx, cancer of
).
Smoking is extremely harmful during
pregnancy.
Babies
of
women
who
smoke are smaller and are less likely to
survive
than
those
of nonsmoking
mothers. Children with parents who
smoke are more likely to suffer from
asthma
or other respiratory diseases.
There is also evidence that
passive
smokers
are at increased risk of tobacco-
related disorders and also suffer dis-
comfort
in
the
form
of coughing,
wheezing, and sore eyes.
Tobacco contains many toxic chemi-
cals.
Nicotine
is the substance that
causes addiction to tobacco. It acts as a
tranquillizer but also stimulates the
release of
adrenaline
into the blood-
stream. This can raise blood pressure.
Tar in tobacco produces chronic irrita-
tion of the respiratory system and is
thought to be a major cause of lung
cancer. Carbon monoxide passes from
the lungs into the bloodstream, where
it easily combines with
haemoglobin
in
red blood cells, interfering with oxy-
genation of tissues. In the long term,
persistently
high
levels
of
carbon
monoxide in the blood cause hardening
of the arteries, which greatly increases
the risk of
coronary thrombosis
.
snails and disease Snails act as host to
various types of fluke that infest humans,
such as
liver flukes
.
SNAILS AND DISEASE
S
515
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