Practice Questions: Answers -- Pulmonary Circulation


1. D. Pulmonary vascular resistance decreases as pulmonary blood flow increases due to increasing blood vessel diameter and recruitment of more blood vessels. Note that choice C is incorrect as high altitude causes pulmonary vasoconstriction due to the low oxygen partial pressure.

2. E. Increase pulmonary capillary permeability will let plasma proteins diffuse into the lung interstitial space, thereby decreasing the osmotic (or oncotic) pressure difference. Remember that it is the osmotic pressure that keeps fluid from leaving the pulmonary capillaries and moving into the interstitial space and alveoli.

3. D. The base of the lungs in the upright posture receives both the most ventilation and the most perfusion.