MediumZoologyBreathing and Exchange of Gases
+4 / -1
The partial pressure of O₂ in the alveolar air is approximately:
A
40 mmHg
B
104 mmHg
C
160 mmHg
D
600 mmHg
Explanation
Alveolar air has a pO₂ of approximately 104 mmHg (vs 160 mmHg in atmospheric air — the difference due to humidification and mixing with residual air). Blood entering pulmonary capillaries has pO₂ of ~40 mmHg. This gradient drives O₂ from alveoli into blood. After exchange, pulmonary venous blood has pO₂ ~95–100 mmHg.
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