artery

An artery is a high-pressure pipe carrying blood away from the heart. A simple memory aid: arteries lead Away. Their walls are thick, muscular and elastic—like a sturdy garden hose built to withstand the forceful, pulsing surges that come with each heartbeat.

Each large artery has three layers: an inner endothelial lining (intima), a thick middle layer of smooth muscle and elastic tissue (media), and an outer connective sheath (adventitia). The elastic walls of big arteries like the aorta stretch during the heart’s contraction and recoil during relaxation, smoothing the pulsatile output into more continuous downstream flow—this is sometimes called the ‘Windkessel’ effect. Smaller muscular arteries and arterioles can actively narrow or widen to control where blood goes.

An important caveat to the usual ‘arteries carry oxygenated blood’ rule: this is true throughout the systemic circulation, but the pulmonary arteries carry deoxygenated blood toward the lungs. So the defining feature of an artery is direction—away from the heart—not its oxygen content.