Arteriosclerosis and atherosclerosis are two different concepts. Arteriosclerosis is a type of vascular disease within arteriosclerosis, but atherosclerosis is more commonly significant clinically. Hence, it is customarily referred to simply as arteriosclerosis, generally implying atherosclerosis. The causes of arteriosclerosis are numerous, but they share common characteristics including thickening, hardening, loss of elasticity, and narrowing of the arterial walls. Atherosclerosis is characterized by lesions starting in the innermost layer of the artery, involving local accumulation of lipids, complex carbohydrates, fibrous tissue proliferation, and calcification forming plaques, along with a gradual degeneration of the innermost layer. The lipid accumulation gives the inner layer a yellowish, porridge-like appearance, hence the name atherosclerosis.