Topic overview

Start with the big picture

Vessel walls share three layers—tunica intima, tunica media, and tunica adventitia—but their proportions and features vary with function. Elastic arteries accommodate pulse pressure, muscular arteries distribute blood, and arterioles regulate systemic vascular resistance. Capillary types support exchange, while metarterioles and precapillary sphincters influence perfusion. Venules begin the return pathway and participate in leukocyte passage; valves in medium veins help limit retrograde flow. The topic also introduces portal systems, arterio-venous anastomoses, blood-volume distribution, and nourishment of large-vessel walls by vasa vasorum. Endothelial signaling and differences in arterial and venous compliance connect vessel structure to vascular tone and hemodynamics.