In human being partial pressure of `CO_(2)` in expired and inspired air is

Options

A. 0.3 mm Hg and 40 mm Hg
B. 32 mm Hg and 0.3 mm Hg
C. 40 mm Hg and 46 mm Hg
D. 40 mm Hg and 0.3 mm Hg

Answer

To determine the partial pressures of carbon dioxide (CO2) in inspired and expired air in humans, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Gas Exchange**:
- In humans, the process of breathing involves two main phases: inspiration (inhaling) and expiration (exhaling). During inspiration, fresh air enters the lungs, and during expiration, air is expelled from the lungs.

2. **Partial Pressure in Inspired Air**:
- Inspired air is the air that we inhale from the atmosphere. This air has a low concentration of carbon dioxide because it has not yet interacted with the body’s metabolic processes. The partial pressure of CO2 in inspired air is approximately **0.3 mmHg**.

3. **Partial Pressure in Expired Air**:
- Expired air is the air that we exhale after the gas exchange has occurred in the lungs. During this process, oxygen is absorbed into the bloodstream, and carbon dioxide, which has accumulated in the body due to metabolic activities, is released into the lungs. As a result, the partial pressure of CO2 in expired air increases significantly to about **40 mmHg**.

4. **Conclusion**:
- Therefore, the partial pressures of CO2 in inspired and expired air are:
- Inspired air: **0.3 mmHg**
- Expired air: **40 mmHg**

### Final Answer:
- The partial pressure of CO2 in inspired air is **0.3 mmHg**, and in expired air, it is **40 mmHg**.

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