EMBOLUS
EMG
internal bleeding or to cut off the blood
supply to a
tumour
.
In the latter case,
the technique 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
both in the skin and the internal organs.
A
catheter
is introduced into a blood
vessel near the one to be blocked and
the
embolus
that will block the vessel is
released through the catheter. Emboli
are made of materials such as blood-
clotting agents or
silicone
.
embolus
A fragment of material, usual-
ly a blood clot, that travels in the
bloodstream and causes obstruction of
an
artery
. An embolus is life-threaten-
ing 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
8
weeks of its development follow-
ing
conception
; for the rest of the
pregnancy it is known as a
fetus
.
The embryo develops from an 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
to form a
spherical mass of cells. About
6
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 will later
become the
placenta
. In the cell mass, a
flat disc forms, consisting of layers of
cells from which all the baby's tissues
will form. The
amniotic sac
develops
around the embryo.
Early in the 3rd week, the head of the
embryo forms and the neural tube,
which will later become the
brain
and
spinal cord
, forms along the embryo's
back. In the 4th week, the neural tube
extends towards the head, where a fold
becomes visible that will eventually
form the brain. Developing ears appear
as pits.
Rudimentary eyes form as
stalks. Within the embryo, buds of tis-
sue form that will 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.
During the 5th week, the external ears
become visible, pits mark the position
of the nose, the jaws form, and the limb
buds extend. Folds of tissue fuse to
form the front wall of the chest and
abdomen. The
umbilical cord
develops.
During weeks
6
-
8
, the face becomes
recognizably human, the neck forms,
the limbs become jointed, and fingers
and toes appear. After
8
weeks, most of
the internal organs have formed and all
external features are present.
EMBRYO
4 WEEKS
20 DAYS
Cardiac
bulge
Umbilical
stalk
Limb
Developing
buds
eye
Head
\
bud
\
embryology
The study of the develop-
ment of the
embryo
and then the
fetus
from
conception
until birth.
emergency
Any condition requiring ur-
gent medical treatment, such as
cardiac
arrest
, or any procedure that must be
performed immediately, such as
cardio-
pulmonary resuscitation
.
emergency contraception
See
con-
traception, emergency.
emesis
The medical term for
vomiting
.
emetic
A substance that causes
vomit-
ing
,
used to
treat
some
types
of
poisoning and drug overdose. The most
widely used emetic is
ipecacuanha
.
EMG
The abbreviation for electromyo-
gram, a recording of electrical activity
in
muscle
.
An EMG can help diagnose
muscle disorders, such as
muscular dys-
trophy
, or disorders in which the nerve
supply to muscle is impaired, such as
neuropathy
or
radiculopathy
.
197
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