The arterial system begins at the left ventricle of the heart with the AORTA, which gives o? branches that subdivide into smaller and smaller vessels. The ?nal divisions, called arterioles, are microscopic and end in a network of capillaries which perforate the tissues like the pores of a sponge and bathe them in blood that is collected and brought back to the heart by veins. (See CIRCULATORY SYSTEM OF THE BLOOD.)
The chief arteries after the aorta and its branches are:
(1) the common carotid, running up each side of the neck and dividing into the internal carotid to the brain, and external carotid to the neck and face;
(2) the subclavian to each arm, continued by the axillary in the armpit, and the brachial along the inner side of the arm, dividing at the elbow into the radial and the ulnar,
which unite across the palm of the hand in arches that give branches to the ?ngers;
(3) the two common iliacs, in which the aorta ends, each of which divides into the internal iliac to the organs in the pelvis, and the external iliac to the lower limb, continued by the femoral in the thigh, and the popliteal behind the knee, dividing into the anterior and posterior tibial arteries to the front and back of the leg. The latter passes behind the inner ankle to the sole of the foot, where it forms arches similar to those in the hand, and supplies the foot and toes by plantar branches.
Structure The arteries are highly elastic, dilating at each heartbeat as blood is driven into them, and forcing it on by their resiliency (see PULSE). Every artery has three coats: (a) the outer or adventitia, consisting of ordinary strong ?brous tissue; (b) the middle or media, consisting of muscular ?bres supported by elastic ?bres, which in some of the larger arteries form distinct membranes; and (c) the inner or intima, consisting of a layer of yellow elastic tissue on whose inner surface rests a layer of smooth plate-like endothelial cells, over which ?ows the blood. In the larger arteries the muscle of the middle coat is largely replaced by elastic ?bres, which render the artery still more expansile and elastic. When an artery is cut across, the muscular coat instantly shrinks, drawing the cut end within the ?brous sheath that surrounds the artery, and bunching it up, so that a very small hole is left to be closed by blood-clot. (See HAEMORRHAGE.)... arteries
Atherosclerosis is due to the deposition of CHOLESTEROL into the walls of arteries. The process starts in childhood with the development of fatty streaks lining the arteries. In adulthood these progress, scarring and calcifying to form irregular narrowings within the arteries and eventually leading to blockage of the vessel. The consequence of the narrowing or blockage depends on which vessels are involved
– diseased cerebral vessels cause strokes; coronary vessels cause angina and heart attacks; renal vessels cause renal failure; and peripheral arteries cause limb ischaemia (localised bloodlessness).
Risk factors predisposing individuals to atherosclerosis include age, male gender, raised plasma cholesterol concentration, high blood pressure, smoking, a family history of atherosclerosis, diabetes and obesity.
Arteritis occurs in a variety of conditions that produce in?ammation in the arteries. Examples include syphilis – now rare in Britain
– which produces in?ammation of the aorta with subsequent dilatation (aneurysm formation) and risk of rupture; giant cell arteritis (temporal arteritis), a condition usually affecting the elderly, which involves the cranial arteries and leads to headache, tenderness over the temporal arteries and the risk of sudden blindness; Takayasu’s syndrome, predominantly affecting young females, which involves the aortic arch and its major branches, leading to the absence of pulse in affected vessels; and polyarteritis nodosa, a condition causing multiple small nodules to form on the smaller arteries. General symptoms such as fever, malaise, weakness, anorexia and weight loss are accompanied by local manifestations of ischaemia (bloodlessness) in di?erent parts of the body.... arteries, diseases of
Atherosclerosis, in which fat deposits build up on artery walls, is the most common arterial disease.
It can involve arteries throughout the body, including the brain (see cerebrovascular disease), heart (see coronary artery disease), and legs (see peripheral vascular disease).
Atherosclerosis is the main type of arteriosclerosis, a group of disorders that cause thickening and loss of elasticity of artery walls.
Hypertension is another common cause of thickening and narrowing of arteries, and it increases the risk of a stroke or kidney failure.
Arteritis is inflammation of artery walls that causes narrowing and sometimes blockage.
Aneurysm is ballooning of an artery wall caused by the pressure of blood flowing through a weakened area.
Thrombosis occurs when a blood clot forms in a blood vessel, causing obstruction of the blood flow.
Blockage of an artery by a fragment of blood clot or other material travelling in the circulation is called an embolism.
Raynaud’s disease is a disorder involving intermittent spasm of small arteries in the hands and feet, usually due to cold.... arteries, disorders of
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