Question

Which of the following statements is wrong?

• A. The partial pressure of $C{O}_2$ is higher in the air inside the lungs than inside the venous blood
• B. The partial pressure of $O_2$ is higher in the air inside the lungs than in the arterial blood.
• C. The partial pressure of $O_2$ is lower inside the venous blood than in the air in the lungs.
• D. The partial pressure of $C{O}_2$ is higher inside the venous blood than in the air inside the lungs.

Answer 1

The correct option is A

The partial pressure of $C{O}_2$ is higher in the air inside the lungs than inside the venous blood

Venous blood is the deoxygenated blood that returns to the lungs after giving out all the oxygen to the tissues. The partial pressure of carbon dioxide reaching the alveolar capillaries is 45 mmHg whereas partial pressure of carbon dioxide in the alveolar air is 40 mmHg. Therefore, $C{O}_2$ rapidly leaves the blood capillaries and enters the alveoli.