How do arterial and venous walls differ structurally?

• A. Arteries have thick tunica media with smooth muscle and elastic fibers; veins have thinner walls, larger lumens, less smooth muscle, and valves.
• B. Arteries have valves; veins lack valves and thick media.
• C. Veins have thicker media; arteries have large lumens.
• D. Arteries and veins identical.

Answer: (B)

Arteries are built to withstand and regulate the high pressure of blood pumped from the heart, so their walls have a thick tunica media rich in smooth muscle and elastic fibers, with a sturdy internal elastic lamina that helps them rebound after each heartbeat. Veins, by contrast, operate at lower pressure and act as blood reservoirs, so their walls are thinner with a relatively large lumen, less smooth muscle, and a prominent outer support layer. They also contain valves, especially in the limbs, to prevent backflow as blood returns to the heart.

So the best description matches arteries having a thick muscular-elastic middle layer, while veins have thinner walls, larger lumens, less smooth muscle, and valves. The idea that arteries have valves is not correct, and the notion that veins lack valves or that arteries have thick media in veins doesn’t fit the anatomy.