Arterial pressure in the pulmonary circulation is much higher than in the systemic circulation because of its proximity to the heart.

• A. True
• B. False
• C. It varies with activity
• D. Only at high altitude

Answer: (B)

Pulmonary arterial pressure is not higher than systemic; it is much lower. The pulmonary circulation is a low-resistance, highly compliant network designed for gas exchange, so the right ventricle only needs to generate modest pressure to push blood through the lungs. In contrast, the systemic circulation has much higher resistance across a large, branched vascular bed, so the left ventricle must pump against a much greater load, producing much higher arterial pressures. Proximity to the heart doesn’t raise pressure; pressure is governed by the resistance the ventricle must overcome and the driving force of the ventricle. Normal mean pulmonary arterial pressure is about 10-20 mmHg, while systemic arterial pressure is around 90-100 mmHg.