Diffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why?

Explanation

The primary site for the exchange of gases is the alveoli.
2. The uptake of `O_(2)` and the release of `CO_(2)`·occur between the blood and tissues by simple diffusion driven by partial pressure gradient of `O_(2)` and `CO_(2)`.
3. Partial pressure is the pressure contnbuted by an individual gas in a mixture of gases. It isrepresented as `pO_(2)` for oxygen and `pCO_(2)` forcarbon- dioxide.
4. Due to pressure gradients, `O_(2)` from the alveoli enters into the blood and reaches the tissues.
5. `CO_(2)` enters into the blood from the tissues andreaches alveoli for elimination.
6. As the solubility of `CO_(2)` is 20---25 times higherthan that of `O_(2)`, the partial pressure of `CO_(2)` ismuch higher than that of `O_(2)`.