Bma Illustrated Medical Dictionary

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 corddevelops.

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.

embryologyThe study of the develop-

ment of the embryoand then the fetus

from conceptionuntil birth.

emergencyAny condition requiring ur-

gent medical treatment, such as cardiac

arrest, or any procedure that must be

performed immediately, such as cardio-

pulmonary resuscitation.

emergency contraceptionSee con-

traception, emergency.

emesisThe medical term for vomiting.

emeticA substance that causes vomit-

ing, used to treat some types of

poisoning and drug overdose. The most

widely used emetic is ipecacuanha.

EMGThe 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

neuropathyor radiculopathy.

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 catheteris introduced into a blood
vessel near the one to be blocked and
the embolusthat will block the vessel is
released through the catheter. Emboli
are made of materials such as blood-
clotting agents or silicone.
embolusA 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).
embrocationA medication rubbed into
the skin in order to relieve muscular or
joint pain.
embryoThe 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
thefallopian tubeto the uterusto 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 brainand
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,

EMBOLUS EMG

E

EMBRYO

Limb

buds

Developing

eye

Cardiac

bulge

Umbilical

stalk

Head

bud

20 DAYS 4 WEEKS