ABDUCTION
A
base of the skull, entering the back of
the eye socket through a gap between
the skull bones.
The abducent nerve may be damaged
in fractures of the base of the skull, or
by disorders, such as tumours, that dis-
tort the brain. Such damage may give
rise to
double vision
or a
squint.
abduction
Movement of a limb away from the cen-
tral line of the body, or of a digit away
from the axis of a limb. Muscles that
carry out this movement are called
abductors. (See also
adduction.)
abductor
Any one of the muscles that carry out
the movement of
abduction.
aberrant
A term meaning abnormal; in medical
usage the word is often applied to a
blood vessel or nerve that deviates from
its normal route.
abetalipoproteinaemia
A rare, inherited
genetic disorder
of
lipo-
protein
(a protein that combines with fats
or other lipids) metabolism. It is inher-
ited in an autosomal recessive manner
and is characterized by
malabsorption
of
fats, acanthocytosis (distorted red blood
cells),
retinopathy
(disease of the retina),
ataxia
(incoordination and clumsiness),
slurred speech, muscle weakness, curva-
ture of the spine,
neuropathy
(peripheral
nerve disease), fatty stools, diarrhoea,
and
failure to thrive
in infancy.
Treatment with high doses of fat sol-
uble
vitamins
(vitamin A,
vitamin D,
vitamin E,
and
vitamin K)
may slow the
progression
of certain
abetalipopro-
teinaemia-related
problems
such
as
retinal degeneration.
ablation
The removal or destruction of diseased
tissue
by
excision
(cutting
away),
cryosurgery
(freezing),
radiotherapy, dia-
thermy
(burning), or
laser treatment.
ablepharia
A
birth defect
in which the eyelids fail to
develop normally, leaving the eyeball
completely covered over.
abnormality
A physical deformity or malformation,
behavioural or mental problem, or vari-
ation from normal in the structure or
function of a body cell, tissue, or organ.
ABO blood groups
See
blood groups
.
abort
A term meaning to terminate a preg-
nancy,
either
spontaneously
(see
miscarriage
) or through medical inter-
vention (see
abortion, induced).
abortifacient
An agent that causes
abortion.
In medical
practice,
abortion
is
induced
using
prostaglandin drugs,
often given in the
form of vaginal pessaries. These cause
the
softening and widening
of the
cervix (neck of the uterus) and mus-
cular contractions of the uterus.
abortion
In medical usage, a term denoting either
spontaneous abortion (see
miscarriage
)
or medically induced termination (see
abortion
,
induced
)
of pregnancy.
(See
also
complete abortion
;
habitual abortion
;
incomplete abortion; septic abortion.)
abortion, induced
Medically induced termination of preg-
nancy. In the UK abortion can legally
be performed up to the 24th week of
pregnancy.
Legally,
abortion may be
performed if continuation of the preg-
nancy would constitute a greater risk to
the woman’s life than the termination,
if the mental or physical health of the
woman or her existing children is at
risk, or if there is a substantial risk of
serious handicap to the baby.
MEDICAL REASONS FOR ABORTION
A doctor may recommend an abortion
if the woman suffers from a life-threat-
ening condition, such as severe heart
disease, chronic kidney disease, or can-
cer, especially of the breast or cervix.
If a serious fetal abnormality is discov-
ered, for example severe developmental
defects (such as
anencephaly)
or chromo-
somal abnormalities
(such as
Down’s
syndrome),
the parents may be offered
the option of a termination. Abortion
may also be recommended if the mother
contracts
rubella
(German measles) dur-
ing early pregnancy.
HOW IT IS DONE
Early abortion
Up to the ninth week of
pregnancy termination may be induced
by treatment with a combination of two
drugs,
mifepristone
and a
prostaglandin
drug.
These
end
the
pregnancy
by
inducing the uterus to contract and
expel the embryo and the placenta; the
process usually takes at least 48 hours.
If this drug treatment is unsuccessful, a
surgical termination will be required.
Until the 12th week, pregnancy may be
terminated by vacuum suction curettage
performed under either a general or a
local anaesthetic (see
anaesthesia, gener-
al
;
anaesthesia, local
). The
cervix
is
dilated with curved metal rods and a
thin plastic tube is inserted into the
uterus. The tube is connected to an
apparatus that sucks out the fetal and
placental tissues.
Recovery is generally fast, although
strenuous activity should be avoided for
several
days. There
is
usually some
bleeding, and occasionally mild cramps,
for up to a week. Menstrual periods
typically return four to six weeks after
the termination. Sexual intercourse can
be resumed after two to three weeks.
Late abortion
Between the
12th and
15 th weeks of pregnancy, either the
suction procedure used in early abor-
tion or the evacuation procedure may
be recommended. In the evacuation
procedure, which is routinely perfor-
med after the 15th week, the uterus is
forced to contract so that the fetus is
expelled, as in natural labour. Contrac-
tions are induced by oral administration
of a dose of mifepristone, followed 36
to 48 hours later by the introduction,
high into the vagina, of a prostaglandin
hormone
pessary. The
prostaglandin
medication may need to be repeated for
the contractions to be maintained.
It usually takes from 12 to 24 hours
for the fetus to be expelled using the
evacuation procedure,
during
which
time the woman is given
analgesic drugs
(painkillers). She usually remains in
hospital for up to 48 hours after com-
pletion of the termination in order to
be monitored for complications.
COMPLICATIONS
If termination is performed by a quali-
fied gynaecologist in a well-equipped
clinic or hospital,
complications are
rare. Infection, resulting in a condition
called
septic abortion,
or serious bleeding
occasionally occur. Repeated termina-
tions
may
increase
the
risk
of
miscarriage
occurring in subsequent
pregnancies; but a single termination is
unlikely to affect future fertility. (See
also
complete abortion; habitual abortion;
incomplete abortion
.)
abrasion
Also called a graze, a
wound
on the sur-
face of the skin that is caused by
scraping or rubbing.
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