The partial pressure of oxygen at alveolar and tissue level is

Options

A. A : 104 m Hg B : 95 mm Hg
B. A : 159 mm Hg B : 95 mm Hg
C. A : 104 mm Hg B : 40 mm Hg
D. A : 159 mm Hg B : 95 mm Hg

Answer

To solve the question regarding the partial pressure of oxygen at the alveolar and tissue levels, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Partial Pressure**: Partial pressure refers to the pressure exerted by a single type of gas in a mixture of gases. In the context of respiration, we are particularly interested in the partial pressure of oxygen (O2) and carbon dioxide (CO2).

2. **Partial Pressure in the Alveoli**: When air enters the lungs, it reaches the alveoli, where gas exchange occurs. The partial pressure of oxygen in the alveoli is approximately **104 mmHg**. This is the pressure exerted by oxygen in the alveolar air.

3. **Partial Pressure in Oxygenated Blood**: After oxygen diffuses from the alveoli into the blood, the partial pressure of oxygen in the oxygenated blood (which is then transported to the tissues) is about **95 mmHg**. This value indicates the amount of oxygen available in the blood after it has passed through the lungs.

4. **Partial Pressure at the Tissue Level**: When the oxygenated blood reaches the tissues, the oxygen is utilized by the cells for metabolic processes. As a result, the partial pressure of oxygen at the tissue level drops to approximately **40 mmHg**. This lower pressure reflects the consumption of oxygen by the tissues.

5. **Conclusion**: Based on the values discussed, we can summarize that:
- At the alveolar level, the partial pressure of oxygen is **104 mmHg**.
- At the tissue level, the partial pressure of oxygen is **40 mmHg**.

### Final Answer:
- The partial pressure of oxygen at the alveolar level is **104 mmHg** and at the tissue level is **40 mmHg**.