Which statement best describes arterial and venous compliance?

• A. Both have equal compliance.
• B. Arteries are highly compliant; veins are stiff with low volume change.
• C. Veins are highly compliant; arteries are less compliant.
• D. Arteries have higher compliance during diastole than veins.

Answer: (C)

Compliance is how much a vessel can expand for a given rise in pressure. Veins have thin walls and a relatively large lumen, so they distend easily when pressure rises, allowing a large increase in volume with only a small pressure change. That makes veins highly compliant and capable of storing most of the blood volume in a low-pressure system. Arteries, on the other hand, have thicker muscular and elastic walls designed to withstand high pressure and to propel blood forward; they don’t distend much for the same pressure change, so their compliance is lower. The idea that arteries would be more compliant, or that arteries are more compliant specifically during diastole, doesn’t fit their structural role or the pressure–volume relationship. Therefore, the statement that veins are highly compliant and arteries are less compliant is best.