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Atherosclerosis is a type of arteriosclerosis. It comes from the Greek words athero (meaning gruel or paste) and sclerosis (hardness). It involves deposits of fatty substances, cholesterol, cellular waste products, calcium and fibrin (a clotting material in the blood) in the inner lining of an artery. The build-up that results is called plaque. Arteriosclerosis is a general term for the thickening and hardening of arteries. Some hardening of arteries normally occurs when people grow older.
Plaque may partially or totally block the blood's flow through an artery. Two things that can happen where plaque occurs are:
Bleeding (hemorrhage) into the plaque
Formation of a blood clot (thrombus) on the plaque's surface. If either of these occurs and blocks the entire artery, a heart attack or stroke may result.
Atherosclerosis affects large and medium-sized arteries. The type of artery and where the plaque develops varies with each person. Atherosclerosis is a slow, progressive disease that may start in childhood. In some people this disease progresses rapidly in their third decade. In others it doesn't become threatening until they're in their fifties or sixties.
How does atherosclerosis start? It's a complex process. Exactly how atherosclerosis begins or what causes it isn't known, but some theories have been proposed. Many scientists think atherosclerosis begins because the innermost layer of the artery becomes damaged. This layer is called the endothelium. Three possible causes of damage to the arterial wall are:
Elevated levels of cholesterol and triglyceride in the blood
High blood pressure
Cigarette smoke greatly aggravates and speeds up the growth of atherosclerosis in the coronary arteries, the aorta and arteries of the legs.
Because of the damage, over time, fats, cholesterol, platelets, cellular debris and calcium are deposited in the artery wall. These substances may stimulate the cells of th...