used to treat
trigeminal nerve The 5th
A trigeminal nerve arises from the
Both nerves divide into 3 branches
that supply sensation to the face, scalp,
nose, teeth, lining of the mouth, upper
, and the front portion of
the tongue. They stimulate
production and contraction of
muscles for chewing.
trigeminal neuralgia A disorder of the
in which brief episodes
of severe, stabbing pain affect the
cheek, lips, gums, or chin on
the face. The disorder usually occurs
over age 50. Pain may come in bouts
that last for weeks at a time. The cause
is uncertain, and pain is often brought
on by touching the face, eating, drink-
ing, or talking.
tried, but often,
effective. If this fails, surgery may help.
trigger finger Locking of
fingers in a bent position due to inflam-
mation of the sheath enclosing the
of the affected finger. The finger is usually
tender at the base and slightly swollen
over the tendon. Treatment involves
local injection of a
or, if this is unsuccessful, surgery.
triglyceride A type of simple fat (see
fats and oils
) made up of a molecule of
and 3 molecules of fatty acids.
Triglycerides are the main type of fat
found in stores of body fat.
trimeprazine Also called alimemazine.
used to relieve
itching in allergic conditions, and as a
in children. Side effects
are typical of antihistamines.
trimester A period of 3 months; human
is conventionally divided into
to treat a range of infections, most com-
monly those of the urinary tract. Possible
side effects include rash, itching, nausea,
vomiting, diarrhoea, and a sore tongue.
trimipramine A tricyclic
used to treat
effects include dry mouth, blurred vision,
dizziness, constipation, and nausea.
triple vaccine See
is used to treat
as an ingredient
of cough and cold remedies, and to
treat or prevent allergic reactions to
certain foods or
sible side effects of triprolidine include
dry mouth, dizziness, difficulty in pass-
ing urine, and
trismus Involuntary contraction of the
jaw muscles, which causes the mouth to
become tightly closed. Commonly known
as lockjaw, it may occur as a symptom
, or acute
and other dental
problems affecting the back teeth. Treat-
ment is of the underlying cause.
trisomy The presence of an extra
within a person's cells, making
3 of a particular chromosome instead of
the usual 2. A fault during
form egg or sperm cells leaves an egg or
sperm with an extra chromosome. When
the egg or sperm takes part in fertiliza-
tion, the resulting embryo inherits an
extra chromosome in each of its cells.
The most common
trisomy is of
Trisomy 18 (Edward's syndrome) and
trisomy 13 (Patau's syndrome) are less
very rare. Partial trisomy, with only part
of a chromosome in triplicate, also
occurs. Full trisomies cause abnorma-
lities such as skeletal and heart defects
Down's syndrome, babies usually die in
early infancy. The effects of partial tri-
somies depend on the amount of extra
chromosomal material present.
Diagnosis is made by
of cells, which may be obtained
from the fetus by
the birth. There is no specific treatment.
Parents of an affected child should seek
trisomy 2 1 syndrome Another name
trochlear nerve The 4th
The 2 trochlear nerves arise in the
on each side of the mid-
through gaps in the skull bones. Each
trochlear nerve controls
erior oblique muscles, which rotate the
eyes downwards and outwards.