JEALOUSY, MORBID
JOINT
and lower teeth together. The wires are
removed after about
6
weeks.
jealousy, morbid
Preoccupation with
the potential sexual infidelity of one's
partner. The sufferer, most often a man,
becomes convinced that his partner is
having an affair. Morbid jealousy is usu-
ally caused by a
personality disorder,
depression,
or
paranoia,
but may also
occur in those suffering from
alcohol dep-
endence
or organic brain syndrome (see
brain syndrome, organic).
jejunal biopsy
A diagnostic test in which
a small piece of tissue is removed from
the lining of the
jejunum
for microscopic
examination. It is especially useful in the
diagnosis of
Crohn's disease, coeliac dis-
ease
,
lymphoma
, and other causes of
malabsorption.
The biopsy is taken using
an
endoscope
passed down the throat
into the small intestine, via the stomach.
jejunum
The middle, coiled section of
the small
intestine
, joining the
duodenum
to the
ileum.
The jejunum's function is
the digestion of food and absorption of
nutrients. It may be affected by
coeliac
disease, Crohn's disease,
and
lymphoma.
jellyfish stings
Stings from jellyfish,
which belong to a group of marine ani-
mals called coelenterates or cnidarians.
Stinging capsules discharge when jelly-
fish tentacles are touched. Usually, the
sting causes only a mildly painful or itchy
rash, but some jellyfish and Portuguese
men-of-war (other members of the same
group) can cause a severe sting. Rarely,
venom may cause vomiting, sweating,
breathing difficulties, and collapse. Dan-
gerous species live mainly in tropical
waters.
Antivenoms
may be available.
jet-lag
Fatigue and interruption of the
sleep-wake cycle caused by disturbance
of normal body
biorhythms
as a result of
flying across different time zones. Jet-lag
provokes daytime sleepiness and
insom-
nia
at night. Other symptoms include
reduced physical and mental activity,
and poor memory. Jet-lag tends to be
worse after an eastward flight (which
shortens the traveller's day) than after a
westward one. Treatment with the pitu-
itary hormone
melatonin
is claimed by
some to reduce the severity of jet-lag.
jigger
An alternative name for a
chigoe
or sand flea.
jogger's nipple
Soreness of the nipple
caused by clothing rubbing against it,
usually during sports such as jogging or
long-distance running. Both men and
women can be affected. Prevention is by
applying petroleum jelly to the nipple
before prolonged running.
joint
The junction between 2 or more
bones. Many joints are highly mobile,
while others are fixed or allow only a
small amount of movement.
Joints in the skull are fixed joints firmly
secured by fibrous tissue. The bone sur-
faces of mobile joints are coated with
smooth
cartilage
to reduce friction. The
joint is sealed within a tough fibrous
capsule lined with synovial membrane
(see
synovium
), which produces a lubri-
cating fluid. Each joint is surrounded by
strong
ligaments
that support it and
prevent excessive movement. Movement
is controlled by muscles that are at-
tached to bone by
tendons
on either
JOINT
Ball and socket joint
Fixed joint
323
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