Why the composition of alveolar air is different from that of atmospheric air?

Explanation

### Step-by-Step Solution:

1. **Understanding Atmospheric Air Composition**:
- Atmospheric air is primarily composed of approximately 21% oxygen (O2), 78% nitrogen (N2), and small amounts of other gases like carbon dioxide (CO2) and argon.

2. **Understanding Alveolar Air Composition**:
- Alveolar air, found in the lungs, has a different composition. It contains about 13.6% oxygen and approximately 5.32% carbon dioxide.

...