Question

During external respiration the PCO2 in the alveolar decreases from ___ mmHg to ___ mmHg

Answer 1

During external respiration, the PCO2 in the alveolar air decreases from 45 mmHg to 40 mmHg as carbon dioxide diffuses from the blood into the lungs.

Step-by-step explanation:

During external respiration, the partial pressure of carbon dioxide (PCO2) in the alveolar air decreases from approximately 45 mmHg to 40 mmHg. This decline occurs because carbon dioxide diffuses from the blood, where its partial pressure is higher, into the alveoli of the lungs, where its pressure is lower. This movement is due to the difference in partial pressures and the high solubility of carbon dioxide. As a result, when blood circulates through the lung capillaries, the carbon dioxide diffuses into the alveoli and is then expelled during exhalation.