Arteriosclerosis is defined as chronic arterial wall change consisting of loss of elasticity or "hardening" and a narrowing of the diameter of the arterial lumen. Atherosclerosis is considered a form of arteriosclerosis.

Atherosclerosis occurs when the inner layers of the vessel (intima and media) accumulate deposits of lipid, lipophages and cholesterol. The thickening of the vessel can lead to arterial occlusion and infarcts. Stenotic lesions are most common and most severe in the coronary arteries.

Click on the heart to view a 50 K enlargement.

Side note for you detail oriented types: Interestingly, atherosclerosis has not been described in cats and is associated with hypothyroidism in dogs.