Maximum amount of oxygen is lost from the blood in

Options

A. arteries
B. Capillaries of body
C. Left atrium of heart
D. Capillaries surrounding alveoli

Answer

To determine where the maximum amount of oxygen is lost from the blood, we can analyze the options provided:

1. **Capillaries surrounding alveoli**: In the alveoli, oxygen from the air enters the blood, and carbon dioxide is released from the blood into the alveoli. Therefore, in this area, oxygen is actually being loaded into the blood rather than lost. Thus, this option is incorrect.

2. **Left atrium of the heart**: The left atrium receives oxygen-rich blood from the lungs. The partial pressure of oxygen in the left atrium is about 100 mm Hg, while in the alveoli it is about 104 mm Hg. The difference in partial pressure indicates that there is a slight loss of oxygen (approximately 4 mm Hg) in the left atrium, but this is not significant compared to other areas. Thus, this option is also incorrect.

3. **Capillaries of the body**: In the capillaries of the body, oxygen is delivered to the tissues, and carbon dioxide is taken up from the tissues into the blood. The partial pressure of oxygen in the capillaries is around 40 mm Hg, which indicates a significant loss of oxygen from the blood to the cells. The loss of oxygen in this area is approximately 60 mm Hg, making this the area where the maximum amount of oxygen is lost. Therefore, this option is correct.

4. **Arteries**: Arteries carry oxygen-rich blood away from the heart to the body. The oxygen content is high in the arteries (around 80 to 100 mm Hg), and they do not experience significant loss of oxygen since they are transporting oxygenated blood. Thus, this option is incorrect.

Based on this analysis, the maximum amount of oxygen is lost from the blood in the **capillaries of the body**.

### Final Answer:
The maximum amount of oxygen is lost from the blood in **capillaries of the body**.