The partial pressure of oxygen in the alveoli of the lungs is

In the alveoli, the partial pressure of \( \text{O}_2 \) is \( 104 \text{ mm Hg} \), whereas in deoxygenated blood entering the lungs it is \( 40 \text{ mm Hg} \). Thus, alveolar \( \text{pO}_2 \) is more than that in the blood.