Partial pressure of `CO_2` in alveoli, oxygenated blood, deoxygenated blood, tissue respectively (in mm Hg) are

Options

A. 40, 40, 40, 40
B. 45, 45, 40, 40
C. 40. 40, 45, 45
D. 45, 45, 45, 45

Answer

To determine the partial pressure of carbon dioxide (CO2) in the alveoli, oxygenated blood, deoxygenated blood, and tissues, we can follow these steps:

### Step-by-Step Solution:

1. **Partial Pressure in Alveoli**:
- The partial pressure of CO2 in the alveoli is approximately **40 mm Hg**. This is because the alveoli are where gas exchange occurs, and CO2 is expelled from the blood into the alveoli.

2. **Partial Pressure in Oxygenated Blood**:
- In oxygenated blood, the partial pressure of CO2 is also around **40 mm Hg**. This is because the blood has just passed through the lungs where CO2 was removed, resulting in a lower concentration.

3. **Partial Pressure in Deoxygenated Blood**:
- In deoxygenated blood, the partial pressure of CO2 increases to about **45 mm Hg**. This is due to the accumulation of CO2 from the tissues as the blood returns to the lungs.

4. **Partial Pressure in Tissues**:
- In the tissues, the partial pressure of CO2 is similar to that in deoxygenated blood, which is also approximately **45 mm Hg**. This reflects the higher concentration of CO2 produced by cellular metabolism.

### Summary of Partial Pressures:
- Alveoli: **40 mm Hg**
- Oxygenated Blood: **40 mm Hg**
- Deoxygenated Blood: **45 mm Hg**
- Tissues: **45 mm Hg**

### Final Answer:
The partial pressures of CO2 in alveoli, oxygenated blood, deoxygenated blood, and tissues are **40 mm Hg, 40 mm Hg, 45 mm Hg, and 45 mm Hg**, respectively.