The partial pressure of oxygen in the alveoli of the lungs is

Options

A. Equal to that in the blood
B. More than that in the blood
C. Less than that in the blood
D. Less than that of carbon dioxide

Answer

To answer the question regarding the partial pressure of oxygen in the alveoli of the lungs, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Partial Pressure**:
- Partial pressure refers to the pressure exerted by a specific gas in a mixture of gases. In the context of the lungs, we are interested in the partial pressure of oxygen (O2) in the alveoli.

2. **Alveolar Air Composition**:
- The air in the alveoli is different from the atmospheric air due to gas exchange processes. The partial pressure of oxygen in the alveoli is influenced by the oxygen that is inhaled and the carbon dioxide that is exhaled.

3. **Typical Values**:
- The typical value for the partial pressure of oxygen in the alveoli is approximately **104 mm Hg**. This value is higher than the partial pressure of oxygen in the blood returning from the tissues, which is about **100 mm Hg**.

4. **Gaseous Exchange**:
- The alveoli are the sites of gas exchange where oxygen diffuses from the alveoli into the blood, while carbon dioxide diffuses from the blood into the alveoli to be exhaled.

5. **Conclusion**:
- Therefore, the partial pressure of oxygen in the alveoli of the lungs is **104 mm Hg**.

### Final Answer:
The partial pressure of oxygen in the alveoli of the lungs is **104 mm Hg**.

---