Answer/ Explanation:
The respiratory system works to humidify incoming air, thereby causing the air present in the alveoli to have a greater amount of water vapor than atmospheric air. Alveolar air contains a greater amount of carbon dioxide and less oxygen than atmospheric air.
- A few other reasons are....
Alveolar air is partially replaced by atmospheric air during each breath
Oxygen is constantly absorbed into the blood from alveoli
Carbon dioxide is diffused into alveoli from blood
As air enters respiratory passages it becomes humidified diluting the inspired gases' partial pressures
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