Question

Select the incorrect statement.

• A. The partial pressure of CO₂ (pCO₂) is higher in the air inside the lungs as compared to venous blood.
• B. The partial pressure of O₂ (pO₂) is higher in the air inside the lungs as compared to venous blood.
• C. The partial pressure of O₂ (pO₂) is lower inside the venous blood than in the air in the lung.
• D. The partial pressure of CO₂ (pCO₂) is higher inside the venous blood than in the air.

Answer 1

Answer: (A)

The partial pressure of O₂ in the atmospheric air is 158 mm of Hg and that of CO₂ is 0.3 mm of Hg. The partial pressure of oxygen pO₂ in alveolar air is 100 mm Hg and it is only 40 mm Hg in the arterial capillaries of the lungs. Therefore, oxygen from the alveolar air rapidly diffuses due to its higher pO₂ into the blood capillaries. Hence, the partial pressure of CO₂ (pCO₂) is lower in the air inside the lungs.