EMBOLIZATION
TREATMENT
If a severe embolism causes the person
to collapse, emergency life-saving mea-
sures are undertaken to maintain the
breathing and circulation (see
cardio-
pulmonary resuscitation
) .
Embolectomy
(surgical removal of the
blockage) may be possible. If the embo-
lus is formed from a blood clot and
surgery
is
not
possible,
thrombolytic
drugs
(drugs that dissolve blood clots)
and
anticoagulant drugs
(drugs that pre-
vent clot formation) may be given.
embolization
Deliberate obstruction of a blood vessel
using an artificial embolus (a fragment
of material carried in the bloodstream)
made of material such as gel foam, PVA
(resin), liquid sclerosants (hardeners),
or medical glue. Embolization is carried
out to stop uncontrollable internal bleed-
ing or to cut off the blood supply to a
tumour
,
especially a
fibroid
.
In the latter
case, embolization can relieve pain; cause
the tumour to shrivel, making surgical
removal easier; or stop the tumour from
spreading. Embolization can also be
used to block flow through vascular
abnormalities such as
haemangiomas
,
in
both the skin and internal organs.
A
catheter
(flexible tube) is introduced
into a blood vessel near the one to be
blocked. An embolus is released through
the catheter; it lodges inside the vessel,
blocking blood flow to the affected area.
embolus
A fragment of material, usually a blood
clot, that is carried in the bloodstream
and obstructs an
artery
.
An embolus is
life-threatening if it blocks blood flow
through a vital artery (see
embolism
) .
embrocation
A medication rubbed into the skin in
order to relieve muscular or joint pain.
embryo
The unborn child during the first eight
weeks of its development following
con-
ception
;
for the rest of the pregnancy it
is known as a
fetus
.
Development of the embryo is gov-
erned
internally
by
genes
inherited
from the parents and externally by fac-
tors such as the mother’s diet and any
drugs taken during pregnancy.
THE FIRST TWO WEEKS
The embryo develops from an
ovum
(egg) that has been fertilized by a
sperm
(see
fertilization
) .
It starts as a single cell,
but divides several times as it travels
along the
fallopian tube
to the
uterus
(womb) to form a spherical mass of cells.
About six days after conception, this
mass becomes embedded in the uterus
lining. At the site of attachment, the
outer layer of cells obtains nourishment
from the woman’s blood; this part w ill
later become the
placenta
.
In the cell
mass, a flat disc forms, consisting of
layers of cells from w hich all the baby’s
tissues w ill form.The
amnioticsac
devel-
ops around the embryo.
THE THIRD
WEEK
Early in the third week, the disc of cells
becomes pear-shaped. The head of the
embryo forms at the rounded end and
the lower spine at the pointed end. A
group of cells develops along the back
of the embryo to form the notochord, a
rod of cells that constitutes the basis for
the spine. From this time onwards, the
embryo has two recognizable halves that
develop more or less symmetrically.
The notochord then furrows and the
edges grow towards each other before
fusing to form the neural tube. Later,
the neural tube w ill develop into the
brain
and
spinal cord
.
THE FOURTH
WEEK
During the fourth week, the embryo’s
back grows more rapidly than its front,
giving it a C-shape. The neural tube
extends towards the embryo’s head,
where a fold that w ill eventually form
the brain becomes visible.
Developing ears appear as pits and
rudimentary eyes form as stalks. W ithin
the embryo, buds of tissue form that
w ill become the lungs, pancreas, liver,
and gallbladder. A heart starts to develop
in the form of a tube. Outer layers of
the embryo begin to form the limb
buds and paired bulges appear on the
sides of the neural tube that w ill even-
tually become the cartilage, bone, and
muscle of the back.
THE FIFTH
WEEK
During the fifth week of pregnancy,
the embryo’s external ears become vis-
ible;
pits mark the position
of the
nose; the jaws form; and the lim b buds
extend, becoming flattened at the ends
where the hands and feet w ill develop.
Folds of tissue fuse to form the front
w all of the chest and abdomen. The
umbilical cord
develops.
THE SIXTH TO
EIGHTH
WEEKS
During weeks six to eight, the embryo’s
face becomes recognizably human, the
neck forms, the limbs become jointed,
and fingers and toes appear.
After eight weeks, the embryo is about
2.5
cm long. Most of the internal organs
have formed and all the external fea-
tures are present.
embryo diagnosis
Also called preimplantation diagnosis, a
procedure carried out on
embryos
at an
early stage of development to determine
whether they are affected by a
genetic
disorder
.
Embryo diagnosis may be car-
ried out following
in vitro fertilization
(IVF) if the parents are known to be
carriers of a specific disorder.
Several eggs are fertilized; they are
grown for a few days in specialized
laboratories until the first two or three
cell
divisions
have
taken
place
and
the clusters contain approximately eight
cells.
One cell from
each cluster is
removed in order for its
DNA
to be
analysed. Embryos that are found to
be healthy can then be implanted in the
mother’s uterus (womb).
embryology
The
study
of the
development
and
growth of the
embryo
and then the
fetus
from
conception
through the months of
gestation until birth.
Embryology is an essential part of a
medical student’s training because it
leads to a greater understanding of the
anatomy of an adult and of the ways in
w hich structural defects in the body
may arise. For example, the occurrence
of congenital heart defects is easier to
understand when the stages of fetal
heart development are explained. (See
also
embryo diagnosis
. )
embryoma of the kidney
An alternative name for
Wilms’ tumour
.
emergency
Any condition requiring urgent medical
treatment, such as
cardiac arrest
(a halt
in the pumping action of the heart), or
any procedure that must be performed
immediately,
such as
cardiopulmonary
resuscitation
.
emergency contraception
See
contraception, emergency.
emesis
The medical term for
vomiting
.
emetic
A substance that causes
vomiting
,
used to
treat some types of poisoning and drug
overdose. Emetics act by stimulating the
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