The Human Body


Artery, one of the tubular vessels that conveys blood from the heart to the tissues of the body. Two arteries have direct connection with the heart: (1) the aorta, which, with its branches, conveys oxygenated blood from the left ventricle to every part of the body; and (2) the pulmonary artery, which conveys blood from the right ventricle to the lungs, whence it is returned bearing oxygen to the left side of the heart (see Heart: Structure and Function). Arteries in their ultimate minute branchings are connected with the veins by capillaries. They are named usually from the part of the body where they are found, as the brachial (arm) or the metacarpal (wrist) artery; or from the organ which they supply, as the hepatic (liver) or the ovarian artery. The facial artery is the branch of the external carotid artery that passes up over the lower jaw and supplies the superficial portion of the face; the hemorrhoidal arteries are three vessels that supply the lower end of the rectum; the intercostal arteries are the arteries that supply the space between the ribs; the lingual artery is the branch of the external carotid artery that supplies the tongue. The arteries expand and then constrict with each beat of the heart, a rhythmic movement that may be felt as the pulse.

Disorders of the arteries may involve inflammation, infection, or degeneration of the walls of the arterial blood vessels. The most common arterial disease, and the one which is most often a contributory cause of death, particularly in old people, is arteriosclerosis, known popularly as hardening of the arteries. The hardening usually is preceded by atherosclerosis, an accumulation of fatty deposits on the inner lining of the arterial wall. The deposits reduce the normal flow of the blood through the artery. One of the substances associated with atherosclerosis is cholesterol. As arteriosclerosis progresses, calcium is deposited and scar tissue develops, causing the wall to lose its elasticity. Localized dilatation of the arterial wall, called an aneurysm, may also develop. Arteriosclerosis may affect any or all of the arteries of the body. If the blood vessels supplying the heart muscle are affected, the disease may lead to a painful condition known as angina pectoris.

The presence of arteriosclerosis in the wall of an artery can precipitate formation of a clot, or thrombus (see Thrombosis). Treatment consists of clot-dissolving enzymes called urokinase and streptokinase, which were approved for medical use in 1979. Studies indicate that compounds such as aspirin and sulfinpyrazone, which inhibit platelet reactivity, may act to prevent formation of a thrombus, but whether they can or should be taken in tolerable quantities over a long period of time for this purpose has not yet been determined.

Embolism is the name given to the obstruction of an artery by a clot carried to it from another part of the body. Such floating clots may be caused by arteriosclerosis, but are most commonly a consequence of the detachment of a mass of fibrin from a diseased heart. Any artery may be obstructed by embolism; the consequences are most serious in the brain, the retina, and the limbs. In the larger arteries of the brain, embolism causes stroke.