Question

fill in the blank question
during external respiration, the pco₂ in alveolar capillaries decreases from mm hg to 40 mm hg.

Explanation:

External respiration involves gas exchange. Blood in alveolar capillaries has a higher \(PCO_2\) (partial pressure of carbon dioxide) than alveolar air. The normal \(PCO_2\) of venous blood (which enters alveolar capillaries) is \(45\) mm Hg, and it decreases to \(40\) mm Hg (the \(PCO_2\) of alveolar air) as \(CO_2\) diffuses from blood to alveoli.

Answer:

\(45\)