SYNDACTYLY
SWEATING
SWEAT GLANDS
Sweat droplet
Sweat
gland
ECCRINE SWEAT GLAND IN SKIN
in hairy areas, particularly the armpits,
pubic region, and around the anus.
The sweat glands are controlled by the
autonomic nervous system.
The glands
are usually stimulated to keep the body
cool, but anxiety or fear can also cause
sweating. Sweat is odourless until bac-
teria act upon it, producing
body odour.
A common disorder of the sweat
glands is
prickly heat.
Other disorders
include
hyperhidrosis
and
hypohidrosis
.
sweating The process by which the body
cools itself. (See also
sweat glands.)
sweeteners,
artificial See
artificial
sweeteners
.
swimmer's ear A common name for
otitis externa
.
sycosis barbae Inflammation of the
beard area due to infection of the hair
follicles, usually with
staphylococcus
AUREUS
bacteria contracted from in-
fected
razors
or
towels.
Pus-filled
blisters appear around the follicles. Treat-
ment is usually with
antibiotic drugs.
Sydenham's chorea A rare childhood
disorder of the
central nervous system
that causes involuntary jerky movements
of the head, face, limbs, and fingers. Vol-
untary movements are clumsy, and the
limbs become floppy. The disorder usu-
ally follows an attack of
rheumatic fever
.
Sydenham's chorea usually clears up
after 2-3 months and has no long-term
adverse effects.
sympathectomy An operation in which
the ganglia (nerve terminals) of sympa-
thetic nerves are destroyed to interrupt
the nerve pathway. This may be per-
formed to improve blood supply to a
limb (as a treatment for
peripheral vas-
cular disease
) or to relieve chronic pain,
for example
causalgia
.
sympathetic nervous system One of
the
2
divisions of the
autonomic nervous
system
. In conjunction with the other
division (the parasympathetic nervous
system), this system controls many of
the involuntary activities of the body's
glands and organs.
symphysis A type of
joint
in which 2
bones are firmly joined by tough carti-
lage. Such joints occur between the
vertebrae;
between the pubic bones at
the front of the
pelvis;
and between the
upper and middle parts of the
sternum
.
symptom An indication of a disease or
disorder that is noticed by the sufferer.
By contrast, the indications that a doc-
tor notes are called signs.
symptothermal method See
contra-
ception, natural methods of
.
synaesthesia A condition in which stim-
ulation of one of the senses (by a sound,
for example) produces an additional
response, such as the appearance of a
colour in addition to the normal per-
ception associated with that stimulus.
synapse A junction between 2
neurons
across which a signal can pass. At a
synapse, the
2
neurons do not come
directly into contact but are separated
by a gap called the synaptic cleft. When
an electrical signal passing along a neu-
ron reaches a synapse, it causes the
release of a chemical called a
neuro-
transmitter
. The neurotransmitter travels
across the synaptic cleft to the surface
membrane of the next neuron, where it
changes the electrical potential of the
membrane. Signals can be transmitted
across a synapse in one direction only.
Most drugs affecting the nervous sys-
tem work as a result of their effects on
synapses. Such drugs may affect the
release of neurotransmitters, or they
may modify their effects.
syncope The medical term for
fainting.
syndactyly A
congenital
defect in which
2
or more fingers or toes are joined.
S
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