Why are capillary walls important for gas exchange?

• A. They are thick and protective
• B. They are selectively permeable to carbon dioxide
• C. They are thin, allowing efficient gas diffusion
• D. They contain several layers of muscle

Answer: (C)

Capillary walls play a crucial role in gas exchange due to their thin structure, which facilitates efficient diffusion of gases. This thinness minimizes the distance that oxygen and carbon dioxide must travel between the blood and surrounding tissues or alveoli in the lungs. The greater the surface area and the thinner the barrier, the more effective the gas exchange process becomes, allowing oxygen to enter the blood while carbon dioxide is expelled effectively.

Additionally, the thin walls of capillaries ensure that a large number of capillaries can exist in a small volume, increasing the overall surface area available for gas exchange. This is essential for meeting the metabolic demands of tissues and maintaining proper physiological function.