What will be the `pO_(2)" and "pCO_(2)` in the atmospheric air compared to those in the alveolar air?

Options

A. `p_(O_(2)) ` lesser , `p_(CO_(2))` higher
B. `p_(O_(2))` higher , `p_(CO_(2))` lesser
C. `p_(O_(2))` higher, `p_(CO_(2))` higher
D. `p_(O_(2))` lesser ,`p_(CO_(2))` lesser

Answer

To compare the partial pressures of oxygen (pO2) and carbon dioxide (pCO2) in atmospheric air and alveolar air, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Partial Pressure**:
- Partial pressure refers to the pressure exerted by a particular gas in a mixture of gases. It is an important concept in understanding how gases diffuse across membranes.

2. **Composition of Atmospheric Air**:
- Atmospheric air is primarily composed of nitrogen (approximately 78%), oxygen (approximately 21%), and a small amount of carbon dioxide (approximately 0.04%).
- Therefore, the pO2 in atmospheric air is relatively high due to the high concentration of oxygen.

3. **Composition of Alveolar Air**:
- Alveolar air has a different composition than atmospheric air because it is saturated with water vapor and contains carbon dioxide that has been released from the blood.
- The pO2 in alveolar air is lower than in atmospheric air due to the mixing of fresh air with the air already present in the alveoli and the presence of carbon dioxide.

4. **Comparison of pO2**:
- In atmospheric air, the pO2 is higher compared to alveolar air. This difference in partial pressure allows oxygen to diffuse from the atmospheric air into the alveoli and subsequently into the bloodstream.

5. **Comparison of pCO2**:
- In atmospheric air, the pCO2 is very low (around 0.04%), while in alveolar air, the pCO2 is significantly higher due to the accumulation of carbon dioxide from metabolic processes.
- This higher pCO2 in alveolar air allows carbon dioxide to diffuse from the blood into the alveoli to be exhaled.

6. **Conclusion**:
- Therefore, we can conclude that:
- **pO2 in atmospheric air > pO2 in alveolar air**
- **pCO2 in atmospheric air < pCO2 in alveolar air**

### Final Answer:
- In atmospheric air, the pO2 is higher and the pCO2 is lower compared to those in alveolar air.