The injured arm
may be supported
horizontally or held
elevated, depend-
ing on the injury.
slipped discSee
disc prolapse.
slipped femoral
epiphysisSee
femoral epiphysis,
slipped.
slit-lampAn 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.)
sloughDead tissue that has been shed
from its original site; for example, loss
of dead skin cells from the skin’s surface.
slow virus diseasesA group of dis-
eases of the central nervous system that
occur many months or even years after
infection with a virus. They causegradual
widespread destruction of nervetissue,
with progressive loss of brain function
and a fatal outcome. Examples include
Creutzfeldt–Jakob diseaseand kuru.
small cell carcinomaOne form of
lung cancer.
smallpoxA highly infectious viral dis-
ease that was declared eradicated in
1980 after a global vaccination campaign.
smearA specimen for microscopic
examination prepared by spreading a
thin film of cells on to a glass slide.
smegmaAn 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.
smellOne 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 systemand 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; hypertrophicrhinitis,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 saltsA preparation of ammo-
niathat was used in the past to revive a
person who felt faint.
smokingSmoking tobaccoin 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
asthmaor other respiratory diseases.
There is also evidence that passive
smokersare 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. Nicotineis the substance that
causes addiction to tobacco. It acts as a
tranquillizer but also stimulates the
release of adrenalineinto 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 haemoglobinin
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 diseaseSnails act as host to
various types of fluke that infest humans,
such as liver flukes.SLIPPED DISC SNAILS AND DISEASES
SLINGELEVATION SLINGInjured
arm