BIRTH DEFECTS
ASPIRATION BIOPSY
1
A fine needle attached to a syringe is
inserted into the lump, and fluid or cells
are sucked outto be examined under a
microscope. The syringe can be held in a
device thatwithdraws the plunger. Usually
no anaesthetic is necessary, but local
anaesthetic may be sometimes be used.
2
Before examination any fluid may be
spun at high speed in a centrifuge and
a small amount placed on a slide.
C e l ls a s
s e e n
t h r o u g h a
m i c r o s c o p e
3
The cells are then fixed (preserved) and
finally stained for viewing. The cytologist
examines individual cells for abnormalities,
paying particular attention to the size,
shape, and structure ofthe nucleus.
OBTAINING RESULTS
Biopsy samples are analysed by
staining;
dyes are used to show up structures or
identify constituents such as
antibodies
or
enzymes.
Tissue may be tested with
specific antibodies in the investigation
of infection and inflammation. In some
cases, a tissue
culture
(cultivation of tis-
sue cells in a growing medium) may be
required. (See also
endometrial biopsy;
excision; kidney biopsy; liver biopsy.)
biorhythms
A term used to describe physiological
functions that vary in a rhythmic way
(for example, the menstrual cycle, which
repeats approximately every 28 days in
fertile women).
Most biorhythms are based on a daily,
or circadian (24-hour), cycle. Our bod-
ies are governed by an internal clock,
which is itself regulated by
hormones
(chemicals released into the circulation
by
endocrine glands).
Periods of sleepi-
ness and wakefulness may be affected
by the level of
melatonin
secreted by the
pineal gland in the brain. Release of
melatonin is stimulated by darkness and
suppressed by light. Cortisol, a hormone
that is secreted by the adrenal glands,
also reflects sleeping and waking states,
being low in the evening and high in
the morning.
When the normal regular division
between night and day is distorted by
air travel to a distant time zone, the
body’s internal clock is disrupted and
the result is
jet-lag.
biosynthesis
The formation of chemical compounds
by a living organism.
biotechnology
The use of living organisms such as
bacteria
in industry and science (for
example, in drug production).
bioterrorism
The use of disease-causing organisms as
an act of violence and intimidation.
Examples of such organisms are
anthrax
spores and the
smallpox
virus.
biotin
A vitamin of the B complex (see
vitamin
B complex)
that is essential for the break-
down of fats.
biphosphonate drugs
See
bisphosphonate drugs
.
bipolar disorder
An illness, commonly known as
manic-
depressive illness,
that is characterized
by swings in mood from severe depres-
sion to overexcitability and vice versa.
bird-fancier’s lung
A form of allergic
alveolitis
(inflamma-
tion of the lungs) caused by inhalation
of dust particles from bird droppings.
The disease is also sometimes known as
pigeon-fancier’s lung.
birth
See
childbirth.
birth canal
The passage through the pelvis, running
from the cervix (the neck of the womb)
to the vaginal opening, through which
the baby passes during
childbirth.
birth control
Limitation of the number of children
born, either to an individual or within a
population.
Family planning
allows men
and women to choose if and when to
have children;
contraception
can prevent
unwanted pregnancies.
birth defects
Abnormalities that are obvious at birth
or detectable early in infancy. Also called
congenital defects, they encompass both
minor abnormalities, such as
birthmarks
,
and serious disorders such as
spina bifida
(failure of the spinal column to close
properly). Birth defects may occur as the
result of a variety of factors, but in most
cases no obvious cause can be found.
CHROMOSOME DEFECTS
Some children are born with more or
fewer than the normal 23
pairs of
chromosomes
(threadlike structures in
the cell nuclei that carry the genetic
information for normal development).
Down’s syndrome,
a condition in which
there is an extra copy of one of the
chromosomes, is one of the most com-
mon
chromosomal abnormalities
.
GENETIC OR HEREDITARY DEFECTS
These may be inherited from one or
both parents (see
gene; genetic disorders).
Genetic defects obvious at birth include
albinism
(lack of normal pigmentation
in the skin, hair, and eyes) and
achon-
droplasia
(abnormally short stature).
DRUGS AND OTHER HARMFUL AGENTS
Certain drugs and chemicals (known as
teratogens
) can damage the fetus if the
mother takes or is exposed to them dur-
ing early pregnancy. Teratogenic drugs
include
thalidomide
(now rarely pre-
scribed) and
isotretinoin,
which is used
in the treatment of severe
acne.
Alcohol
can affect the development of the brain
and face (see
fetal alcohol syndrome).
IRRADIATION
Irradiation of the embryo at an early
stage of development, for example, if a
woman is X-rayed before she is aware of
her pregnancy, can cause abnormalities.
INFECTIONS
If a woman contracts certain infections
during pregnancy, there is a chance that
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