Which statement about veins is true?

• A. Veins carry blood away from the heart under high pressure.
• B. Veins have thinner walls than arteries and a wider lumen.
• C. The largest vein is the aorta.
• D. Cranial vena cava drains blood from the hind limbs.

Answer: (B)

Veins and arteries are built to suit their jobs in circulating blood. Arteries carry blood away from the heart under high pressure, so their walls are thick and muscular to withstand force and to recoil after each heartbeat. Veins, on the other hand, return blood to the heart at much lower pressure. To accommodate large volumes of blood with less pressure, veins have thinner walls and a wider lumen. The wide lumen reduces resistance and lets veins serve as a reservoir, with valves in many veins helping prevent backflow as blood moves slowly and gravity can pull it downward, especially in the limbs.

So, the statement that veins have thinner walls than arteries and a wider lumen is true. For context, the cranial vena cava drains blood from the head and forelimbs, while the hind limbs drain through the caudal (posterior) vena cava; the largest vessel overall is an artery, the aorta, not a vein.