any of a group of diseases characterized by thickening and loss of elasticity of the arterial walls; popularly called “hardening of the arteries.” Symptoms depend on the organ system involved.

The term Arteriosclerosis applied to a group of diseases that affect the elasticity of the blood vessels. It may refer to atherosclerosis, hyperplastic arteriosclerosis, or Mönckeberg's sclerosis. These degenerative processes generally affect only the tunica media and tunica intima. The effect is narrowing of the lumen of a blood vessel, causing rupture of the blood vessel or ischemia of an area of tissue that the vessel supplies.

There are three main forms of arteriosclerosis: 

(1) atherosclerosis, the most common type, in which plaques of fatty deposits form in the inner layer (tunica intima) of the arteries; 

(2) Mönckeberg's arteriosclerosis, called also medial calcific sclerosis because of involvement of the middle layer (tunica media) of the arteries, where there is destruction of muscle and elastic fibers and formation of calcium deposits; and 

(3) arteriolar sclerosis or arteriolosclerosis, which is marked by thickening of the walls of arterioles. All three forms may be present in the same patient, but in different blood vessels. When reference is made to hardening of the arteries, this usually refers to atherosclerosis; the terms arteriosclerosis and atherosclerosis are often used interchangeably.