DIAPHYSIS
D
ribs, and sternum (breastbone). It has
openings for the oesophagus and major
nerves and blood vessels.
The diaphragm plays an important
role in breathing. During inhalation, its
muscle fibres contract, causing it to
move downwards and drawing air into
the lungs. During exhalation, the dia-
phragm muscle relaxes and it moves
upwards, causing air to leave the lungs.
(See also
breathing.)
diaphysis
The shaft, or central portion, of a long
bone, such as the
femur
(thigh-bone).
During bone formation, the
epiphysis
(end of the long bone) develops inde-
pendently from the diaphysis, as they
are initially separated by a mass of car-
tilage known as the epiphyseal plate.
The diaphysis and epiphysis eventually
fuse to form a complete bone.
diarrhoea
An increase in the fluidity, frequency, or
volume of bowel movements, as comp-
ared to the usual pattern for a particular
individual. Diarrhoea may be acute or
chronic. The condition can be very seri-
ous in infants and in elderly people
because of the risk of severe, potentially
fatal,
dehydration.
CAUSES
Acute diarrhoea is usually a result of
consuming food or water contaminated
w ith certain bacteria or viruses (see
food poisoning).
Infective
gastroenteritis
also
causes
diarrhoea
and
may
be
acquired as a result of droplet infec-
tion. Other causes of acute diarrhoea
include anxiety and, less commonly,
amoebiasis, shigellosis, typhoid fever
and
paratyphoid fever,
drug
toxicity,
food
allergy,
and
food intolerance.
Chronic
diarrhoea
generally
takes
the form of repeated attacks of acute
diarrhoea. Such a pattern may be the
result of an intestinal disorder such as
Crohn’s disease, ulcerative colitis,
cancer
of the colon (see
colon, cancer of),
or
irritable bowel syndrome.
Diarrhoea that
recurs, persists for more than a week,
or is accompanied by blood requires
medical investigation.
TREATMENT
The water and electrolytes (salts) lost
during a severe attack of diarrhoea
need to be replaced to prevent dehy-
dration.
Ready-prepared
powders
of
electrolyte
mixtures
can
be
bought
from chemists (see
rehydration therapy).
Antidiarrhoeal drugs,
such as
diphenoxy-
late
and
loperamide
may help if the diar-
rhoea is disabling. They should not,
however, be used to treat attacks of
diarrhoea in children.
diastole
The period in the heartbeat cycle when
the heart muscle is at rest; it alternates
with
systole
,
the period of muscular
contraction. (See also
cardiac cycle
) .
diastolic pressure
The lowest level of
blood pressure
mea-
sured in the main arteries. Diastolic
pressure is the pressure between heart-
beats, when the
ventricles
(the lower
chambers of the heart) are relaxed and
filling with blood. Systolic pressure, the
highest level of blood pressure in the
main arteries, occurs when the ventri-
cles of the heart contract.
The normal range of blood pressure
varies with age and between individu-
als, but a young adult usually has a
diastolic pressure of about 80 mmHg
(mm of mercury) and a systolic pres-
sure of about 120 mmHg. A persistently
high diastolic pressure occurs in most
cases of
hypertension
.
diathermy
The production of heat in a part of the
body
using
high-frequency
electric
currents or microwaves. Diathermy can
be used to increase blood flow and to
reduce some types of deep-seated pain,
for example in rheumatic or arthritic
conditions. Diathermy can also be used
to destroy tumours and diseased areas
of tissue without causing bleeding. A
diathermy knife is used by surgeons to
coagulate bleeding vessels or to sepa-
rate tissues without causing them to
bleed (see
electrocoagulation
) .
diathermy, short-wave
See
short-wave diathermy
.
diathesis
A predisposition towards certain disor-
ders. For example, a bleeding diathesis
is
present
when
a
bleeding disorder
(such as haemophilia) makes a person
susceptible to prolonged bleeding after
an injury. A diathesis may be inherited
or it may be acquired as a result of an
illness or an injury.
diazepam
One of the
benzodiazepine drugs
,
used
mainly for the short-term treatment of
anxiety
and
insomnia
.
Diazepam is also
prescribed as a
muscle-relaxant drug
,
as
an
anticonvulsant drug
in the emergency
treatment of
epilepsy
,
and to treat alco-
hol withdrawal symptoms in people
w ho are dependent on alcohol. It may
also be administered intravenously in
order to produce sedation in people
undergoing certain medical procedures,
such as
endoscopy
.
Diazepam
may
cause
drowsiness,
dizziness,
and
confusion;
therefore,
driving and hazardous work should be
avoided w hile taking the drug. Alcohol
increases the sedative
effects
of the
drug, and should not be consumed
w hile diazepam is being used.
Like other benzodiazepines, diaze-
pam can be habit-forming if it is taken
regularly, and its effects dim inish with
prolonged use. Individuals who have
been
taking
diazepam
regularly
for
more than two weeks should never stop
their treatment suddenly; instead, they
should gradually decrease the dose of
the drug, under medical supervision, in
order to avoid withdrawal symptoms
(such as anxiety, sweating, or, rarely,
after large doses,
seizures
).
DIC
See
disseminated intravascularcoagulation
.
diclofenac
A
nonsteroidal
anti-inflammatory
drug
(NSAID) that is used to relieve pain and
stiffness in
arthritis
and to hasten recov-
ery following injury
to
muscles
or
ligaments. Possible adverse effects of
the drug include nausea, abdominal
pain, and peptic ulcer.
Didronel
A brand name for disodium etidronate
(see
etidronate, disodium
), w hich is a
bisphosphonate drug
.
Didronel is used to
treat bone disorders such as
Paget’s dis-
ease
and
osteoporosis
.
diet
See
nutrition
.
diet and disease
A variety of diseases are linked with
diet. Diseases due to a deficiency of
nutrients
are a major problem in poor
countries.
In
children,
starvation
or
malnutrition may result in
marasmus
or
kwashiorkor
,
w hile vitamin deficiencies
may cause
rickets
or
keratomalacia
(a
condition that causes blindness). Vita-
m in deficiencies may lead to
beriberi
,
pellagra
,
or
scurvy
.
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