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 partial pressure of oxygen (pO₂) in the alveoli and tissues, 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. It is a measure of the concentration of that gas. In the context of respiration, we are particularly interested in the partial pressures of oxygen (O₂) and carbon dioxide (CO₂).

2. **pO₂ in Alveoli**:
- The alveoli are the air sacs in the lungs where gas exchange occurs. When we inhale, oxygen enters the alveoli, leading to a high concentration of oxygen.
- The typical value of pO₂ in the alveoli is approximately **104 mm Hg**.

3. **pO₂ in Tissues**:
- Tissues utilize oxygen for metabolic processes, which leads to a decrease in the concentration of oxygen in the tissues. As cells consume oxygen, the partial pressure of oxygen in the tissues is lower than that in the alveoli.
- The typical value of pO₂ in tissues is approximately **40 mm Hg**.

4. **Conclusion**:
- Therefore, the values of pO₂ in alveoli and tissues are **104 mm Hg** and **40 mm Hg**, respectively.

### Final Answer:
- pO₂ in alveoli: **104 mm Hg**
- pO₂ in tissues: **40 mm Hg**

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