What is the middle layer of a blood vessel wall called?

The middle layer of a blood vessel wall is known as the tunica media. This layer is primarily composed of smooth muscle cells and elastic fibers, which allow the blood vessel to regulate its diameter and, consequently, control blood flow and pressure. The contraction and relaxation of the smooth muscle in the tunica media are essential for vasoconstriction and vasodilation, processes vital for maintaining adequate blood circulation and responding to the body's changing demands.

The presence of elastic fibers in the tunica media is especially important in larger arteries, where these fibers assist in accommodating the surge of blood following each heartbeat. This layer's structural and functional characteristics make it a critical component in the overall functionality of the vascular system.