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 determine 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 particular gas in a mixture of gases. In the context of the lungs, we are focusing on the partial pressure of oxygen (O2).

2. **Identify the Partial Pressure Values**:
- The partial pressure of oxygen in the alveoli is approximately 104 mm Hg.
- The partial pressure of oxygen in the oxygenated pulmonary venous blood is about 100 mm Hg.

3. **Comparison of Partial Pressures**:
- Compare the partial pressure of oxygen in the alveoli (104 mm Hg) with that in the blood (100 mm Hg).
- Since 104 mm Hg (alveoli) is greater than 100 mm Hg (blood), we can conclude that the partial pressure of oxygen in the alveoli is higher than that in the blood.

4. **Understanding the Implications**:
- The higher partial pressure of oxygen in the alveoli facilitates the diffusion of oxygen into the blood. This is essential for gas exchange, as oxygen moves from an area of higher concentration (alveoli) to an area of lower concentration (blood).

5. **Conclusion**:
- Therefore, the correct answer to the question is that the partial pressure of oxygen in the alveoli of the lungs is **more than that in the blood**.

### Final Answer:
The partial pressure of oxygen in the alveoli of the lungs is **more than that in the blood**.

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