Although many quarts of blood pass through the heart each day, the heart cannot utilize the blood within itself, but rather is sustained by branches of arteries originating externally. These coronary arteries can become blocked by the deposition of fatty material (inlcuding cholesterol), connective tissue fibers, and calcium deposited in the vessel walls. If the blockage is severe, numerous heart muscle cells become oxygen starved and the heart stops. In less sever cases, only part of the heart muscle dies as a result of the blockage. The dead muscle is replaced by scar tissue and the heart continues to function, though less efficiently. Diet, stress, smoking, and alcohol all contribute to the problem of heart attacks. Interestingly, although fats in the diet are often blamed for the heart attacks, about 70% of the heart’s energy requirement normally is derived from oxidation of fatty acids. -Biology by Norstog and Meyerriecks

Coronary arteries can become blocked by