Arteries

Arteries are the vessels that carry blood away from the heart. With the exception of the pulmonary arteries (which carry deoxygenated blood to the lungs), they transport oxygen-rich blood to the body's tissues. Because they receive blood directly from the pumping heart, arteries are built to handle high, pulsatile pressure.

Wall Structure

Like most blood vessels, an artery wall has three concentric layers, or tunics. The innermost tunica intima is a thin lining of flat endothelial cells resting on connective tissue, with an internal elastic membrane. The middle tunica media is the thickest layer in arteries and contains circularly arranged smooth muscle and elastic fibers; this layer lets the vessel change its diameter and gives arteries their strength and recoil. The outer tunica adventitia (externa) is connective tissue carrying tiny nerves (nervi vasorum) and small nourishing vessels (vasa vasorum) that supply the wall itself.

Types and Function

Large elastic (conducting) arteries near the heart, such as the aorta, are rich in elastic fibers that stretch and recoil to smooth out blood flow. Medium muscular (distributing) arteries have more smooth muscle and direct blood to specific organs. The smallest arteries, the arterioles, act as resistance vessels: by contracting or relaxing their smooth muscle, they regulate how much blood reaches the capillaries and play a major role in setting blood pressure. This combination of conduction, distribution, and resistance lets the arterial system deliver blood precisely where it is needed.

Clinical Relevance

The most common arterial disease is atherosclerosis, in which fatty plaques build up in the intima and narrow or harden the vessel, reducing blood flow. This underlies coronary artery disease, peripheral artery disease, and many strokes. Chronically elevated pressure within arteries is hypertension, a major risk factor for heart attack and stroke. This is general educational information, not medical advice.