TWINS, CONJOINED
TYPING
TWINS
when
2
eggs are fertilized at the same
time. They each have a placenta and
may be of different sexes. Twins occur in
about 1 in 80 pregnancies. (See also
pregnancy, multiple
.)
twins, conjoined Identical
twins
physi-
cally joined due to a failure to separate
during development from a single fertil-
ized egg. Also called
Siamese twins.
twitch See
fasciculation; tic.
tympanic membrane The medical term
for the
eardrum.
tympanometry A type of
hearing test
used to establish the cause of conduc-
tive
deafness.
During the test, a probe
that contains a tone generator, a micro-
phone, and an air pump is introduced
into the outer-ear canal. The air pres-
sure in the ear is varied and tones are
played into it. The tone pattern reflect-
ed from the
eardrum
and received by
the microphone sreveals whether the
eardrum is moving normally. The test is
particularly useful in children because it
does not rely on a response from the
person being tested.
tympanoplasty An operation on the
ear
to treat conductive
deafness
by
repairing a hole in the eardrum (see
myringoplasty
) or by repositioning or
reconstructing diseased
ossicles
.
typhoid fever An infectious disease
contracted by eating food or drinking
water contaminated with the bacterium
salmonella
typhi.
Typhoid
fever
is
spread by drinking water contaminated
with
sewage,
by
flies carrying the
bacteria from fae-
ces to food, or by
infected
people
handling food.
The 1st symptom,
severe
headache,
occurs 7-14 days
after infection and
is followed by fever,
loss
of
appetite,
malaise
, abdominal
tenderness, consti-
pation, and often
delirium. Diarrhoea
soon develops. In
the
2
nd week of ill-
ness,
pink
spots
develop on the chest and abdomen,
and the liver and
spleen
enlarge. Diag-
nosis is confirmed by a
blood test
or by
obtaining a
culture
of typhoid bacteria
from blood, faeces, or urine. Treatment
is with
antibiotic drugs.
In rare cases,
the bacterium continues to be excreted
after recovery has taken place.
typhus Any of a group of infectious dis-
eases with similar symptoms that are
caused by
rickettsiae
and are spread by
insects or similar animals.
Except in some highland areas of
tropical Africa and South America, epi-
demic typhus is rare today. Endemic
typhus, also called murine typhus, is a
disease of
rats
that is occasionally
spread to humans by fleas; sporadic
cases occur in North and Central Amer-
ica. Scrub typhus is spread by
mites
and
occurs in India and Southeast Asia.
The symptoms and complications of
all types of typhus are similar. Severe
headache, back and limb pain, cough-
ing, and constipation develop suddenly
and are followed by high
fever,
a
measles-like rash, confusion, and pros-
tration. Left untreated, the condition
may be fatal, especially in elderly or
debilitated people.
A diagnosis is made by
blood tests
,
and treatment is with
antibiotic drugs
and supportive treatment.
typing A general term for procedures by
which blood or tissues are classified
(see
blood groups
;
tissue-typing
).
565
previous page 563 BMA Illustrated Medical Dictionary read online next page 565 BMA Illustrated Medical Dictionary read online Home Toggle text on/off