Bma Illustrated Medical Dictionary

and lower teeth together. The wires are
removed after about 6 weeks.
jealousy, morbidPreoccupation 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-
endenceor 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 jejunumfor 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 endoscopepassed down the throat
into the small intestine, via the stomach.
jejunumThe 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 stingsStings 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. Antivenomsmay be available.
jet-lagFatigue and interruption of the
sleep–wake cycle caused by disturbance
of normal body biorhythmsas a result of
flying across different time zones. Jet-lag
provokes daytime sleepiness and insom-
niaat 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 melatoninis claimed by
some to reduce the severity of jet-lag.
jiggerAn alternative name for a chigoe
or sand flea.

jogger’s nippleSoreness 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.

jointThe 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 cartilageto 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 ligamentsthat support it and

prevent excessive movement. Movement

is controlled by muscles that are at-

tached to bone by tendonson either

JEALOUSY, MORBID JOINT

J

JOINT

BALL AND

SOCKET JOINT

ELLIPSOIDAL

JOINT

HINGE JOINT

SADDLE

JOINT

PIVOT JOINT

Pivot joint

(upper neck)

Fixed joint

(skull)

Saddle joint

(base of

thumb)

Ball and socket joint

(shoulder joint)

Ellipsoidal joint

(wrist joint)

Hinge joint

(knee joint)