What is atherosclerosis:
Atherosclerosis is a type of arteriosclerosis caused by a build-up of plaque in the inner lining of an artery. (Arteriosclerosis is a general term for thickening or hardening of the arteries.) It is a slow, progressive disease that may start as early as childhood. The disease has the potential to progress rapidly, or may not become threatening for several decades.

Complications of atherosclerosis:
Plaque is made up of deposits of fatty substances, cholesterol, cellular waste products, calcium, and fibrin. The artery and place within it that the plaque develops varies. The plaque may partially or totally block the blood’s flow through an artery, causing: 

When a hemorrhage or thrombus causes a blockage of  the entire artery, a heart attack or stroke (brain attack) may result. 

What causes atherosclerosis:
It is unknown exactly how atherosclerosis begins or what causes it. Some scientists think it begins when the innermost layer of the artery, called the endothelium, becomes damaged by:

How does the disease progress:
Over time fats, cholesterol, fibrin, platelets, cellular debris and calcium are deposited in the artery wall at the damaged area. The substances can stimulate the cells of the artery wall to produce still other substances and result in further accumulation and division of cells causing atherosclerotic lesions to form. At the same time, fat builds up within these cells and around them and also forms connective tissue. The innermost layer of the artery becomes thickened by these accumulating cells and surrounding material. When the wall is thickened sufficiently, the diameter of the artery will be reduced and the amount of blood decreased, thus decreasing the oxygen supply. If the oxygen supply to the heart muscle is reduced, a heart attack can occur. If the oxygen supply to the brain is cut off, a stroke can occur. And, if the oxygen supply to the extremities occurs, gangrene can result.