Bma Illustrated Medical Dictionary

diverticular diseaseand cancer of the

intestine (see colon, cancer of; rectum,

cancer of). Vegetarian diets are low in

fats, especially saturated fats (which may

contribute to coronary artery disease

and possibly some forms of cancer).

These diets are also likely to contain

less sodiumand more potassium, and

vegetarians tend to have lower blood

pressure than people who eat meat.

vegetative stateA term that is some-

times used to describe a type of

indefinite deep coma. Although the

eyes may be open and occasional ran-

dom movements of the head and limbs

may occur, there are no other signs of

consciousness, and there is no respon-

siveness to stimuli. Only the basic

functions, such as breathing and heart-

beat, are maintained.

veinA vessel that returns blood towards

the heartfrom the various organs and

tissues of the body. The walls of veins,

like those of arteries, consist of a

smooth inner lining, a muscular middle

layer, and a fibrous outer covering.

However, blood pressure in veins is

lower than in arteries, and the walls of

veins are thinner, less elastic, less mus-

cular, and weaker than those of arteries.

The linings of many veins contain folds,

which act as valves, ensuring that blood

flows only towards the heart. Blood is

helped on its way through the veins by

pressure on the vessel walls from the

contraction of surrounding muscles.

(See also circulatory system.)

veins, disorders ofCommon disorders

affecting veinsinclude varicose veins,

deep vein thrombosis (see thrombosis,

deep vein), and thrombophlebitis.

vena cavaEither of 2 large veinsinto

which all circulating (deoxygenated) blood

drains. The venae cavae (superior and

inferior) deliver blood to the right atrium

of the heartfor pumping to the lungs.

The superior vena cava starts at the top

of the chest, close to the sternum, and

passes down through the pericardium

before connecting to the right atrium. It

collects blood from the upper trunk,

head, neck, and arms. The inferior vena

cava starts in the lower abdomen and

travels upwards in front of the spine,

behind the liver, and through the dia-

phragmbefore joining the right atrium.

It collects blood from the legs, pelvic

organs, liver, and kidneys.

venepunctureA common procedure in

which a vein, usually in the forearm, is

pierced with a needle to inject fluid or

withdraw blood. A tourniquetis used to

swell the veins, and a sterile needle is

inserted. A syringe is attached to the

needle if bloodis to be taken or medica-

tion injected. For intravenous infusion, a

cannula (tube) is insertedvia the needle.

After the fluid has been injected or

withdrawn, the needle or cannula is

removed. The area is then covered and

VEGETATIVE STATE VENEPUNCTURE

V

VEIN

Outer layer

Inner lining

Valve flap

Muscle layer

STRUCTURE OF A VEIN

Carotid artery

Subclavian

artery

Subclavian

vein

Aorta

Jugular vein

VENA CAVA

Inferior

vena cava

Superior

vena cava

Heart