The blood vessels that carry O2-rich blood from the heart to different parts of the body are called arteries. Arteriosclerosis is the hardening and loss of elasticity of the artery walls. In arteriosclerosis, calcium and cholesterol accumulate in the artery walls and the amount of fibrous tissue increases. Arteriosclerosis is the narrowing of the lumen of arteries and arterioles. Arteriosclerosis is caused by accumulation of fatty substances or cholesterol in the cavities of arteries and arterioles. Atherosclerotic plaque is the accumulation of fatty material caused by arteriosclerosis.