What is the value of `pO_(2)` in alveoli and tissues
respectively?

Options

A. 104 mm Hg and 150 mm Hg
B. 45 mm Hg and 0.3 mm Hg
C. 104 mm Hg and 40 mm Hg
D. 95 mm Hg and 159 mm Hg

Answer

To determine the values of \( pO_2 \) (partial pressure of oxygen) in the alveoli and tissues, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Partial Pressure**:
- Partial pressure (\( pO_2 \)) is a measure of the concentration of oxygen in a mixture of gases. It indicates how much pressure is exerted by oxygen in that mixture.

2. **Role of Alveoli in Gas Exchange**:
- Alveoli are the primary sites for gas exchange in the lungs. They receive oxygen from atmospheric air, which has a higher concentration of oxygen compared to the blood in the pulmonary capillaries.

3. **Oxygen Movement**:
- Oxygen moves from areas of higher concentration to areas of lower concentration. Therefore, in the alveoli, where the \( pO_2 \) is higher, oxygen diffuses into the blood, which has a lower \( pO_2 \).

4. **Comparing Alveoli and Tissues**:
- In the tissues, the \( pO_2 \) is lower because the cells are constantly using oxygen for metabolic processes. This creates a gradient that allows oxygen to diffuse from the blood (higher \( pO_2 \)) into the tissues (lower \( pO_2 \)).

5. **Typical Values**:
- The typical value of \( pO_2 \) in the alveoli is approximately **104 mmHg**.
- The typical value of \( pO_2 \) in the tissues is approximately **40 mmHg**.

6. **Conclusion**:
- Therefore, the values of \( pO_2 \) in the alveoli and tissues are approximately **104 mmHg** and **40 mmHg**, respectively.

### Final Answer:
- \( pO_2 \) in alveoli: **104 mmHg**
- \( pO_2 \) in tissues: **40 mmHg**

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