Question

Compared to the atmospheric air, the alveolar air has

• A. more $pO_2$ and less $pCO_2$
• B. less $pO_2$ and more $pCO_2$
• C. more $pO_2$ and more $pCO_2$
• D. less $pO_2$ and less $pCO_2$

Answer 1

Answer: (B)

The partial pressure of oxygen in atmospheric air is higher than that of oxygen in alveolar air. In atmospheric air, $p O _{2}$ is about $15, mm\,Hg$. In alveolar air, it is about $104\, mm\, Hg$.
The partial pressure of $CO _{2}$ in atmospheric air is lesser than that of $CO _{2}$ in alveolar air. In atmospheric air, $p CO _{2}$ is about $0.3\, mm\, Hg$. In alveolar air, it is about $40 \,mm \,Hg$.