Which term describes the body's adjustment to redirect blood flow from poorly ventilated lung regions to better-ventilated regions to improve gas exchange?

Which term describes the body's adjustment to redirect blood flow from poorly ventilated lung regions to better-ventilated regions to improve gas exchange?

• A. Bronchodilation
• B. Pulmonary edema
• C. Hypoxic pulmonary vasoconstriction
• D. Vasodilation

Answer: (C)

The key idea is that the lungs actively optimize gas exchange by adjusting blood flow to match how well each region is ventilated. When alveolar oxygen is low in a patch of lung, the small pulmonary arteries in that area constrict. This hypoxic pulmonary vasoconstriction reduces blood flow to poorly ventilated units and shunts it toward better-ventilated regions, improving the overall ventilation-perfusion balance and thus gas exchange. Bronchodilation changes the airways and thus ventilation, not the distribution of blood flow. Pulmonary edema involves fluid buildup that impairs gas exchange rather than directing blood away from poorly ventilated areas. General vasodilation would increase blood flow broadly and could worsen V/Q mismatch instead of correcting it. The specific, localized response to low oxygen in alveoli that redirects perfusion is hypoxic pulmonary vasoconstriction.

The key idea is that the lungs actively optimize gas exchange by adjusting blood flow to match how well each region is ventilated. When alveolar oxygen is low in a patch of lung, the small pulmonary arteries in that area constrict. This hypoxic pulmonary vasoconstriction reduces blood flow to poorly ventilated units and shunts it toward better-ventilated regions, improving the overall ventilation-perfusion balance and thus gas exchange.

Bronchodilation changes the airways and thus ventilation, not the distribution of blood flow. Pulmonary edema involves fluid buildup that impairs gas exchange rather than directing blood away from poorly ventilated areas. General vasodilation would increase blood flow broadly and could worsen V/Q mismatch instead of correcting it. The specific, localized response to low oxygen in alveoli that redirects perfusion is hypoxic pulmonary vasoconstriction.