- The intima, the inner layer lined by a smooth tissue called endothelium
- The media, a layer of muscle that lets arteries handle the high pressures from the heart
- The adventitia, connective tissue anchoring arteries to nearby tissues
The largest artery is the aorta, the main high-pressure pipeline connected to the heart's left ventricle. The aorta branches into a network of smaller arteries that extend throughout the body. The arteries' smaller branches are called arterioles and capillaries. The pulmonary arteries carry oxygen-poor blood from the heart to the lungs under low pressure, making these arteries unique.
Arteriosclerosis is hardening and thickening of the walls of the arteries. Arteriosclerosis can occur because of fatty deposits on the inner lining of arteries (atherosclerosis), calcification of the wall of the arteries, or thickening of the muscular wall of the arteries from chronically elevated blood pressure. Atherosclerosis is a progressive disease that is characterized by a buildup of plaque within the arteries. Plaque is formed from fatty substances, cholesterol, cellular waste, calcium, and fibrin. Plaque may partially or totally block the blood's flow through an artery. Two things can happen: bleeding into the plaque, or formation of a clot on the surface of the plaque. If either of these happens and blocks the artery, a heart attack or stroke may result.
Sources: WebMD, Franklin Institute