In the systemic circulation, arterioles account for one half of the total resistance. What fraction is accounted for by the rest of the circulation?

• A. 1/3
• B. 1/2
• C. 1
• D. 2/3

Answer: (B)

The main idea is how vascular resistance is distributed in the systemic circulation. Arterioles contribute about half of the total resistance because their small diameter creates a large drop in pressure. The rest of the circulation — the larger arteries, capillaries, and veins — collectively provide the other half of the total resistance. Since the total resistance is the sum of all parts, if arterioles account for one half, the remainder must also account for one half. This division reflects why most of the pressure drop occurs across the arterioles, while the bulk of the network beyond them is more compliant and contributes the remaining resistance.