Which among the following do not come under blood vessel?

Options

A. Arteries
B. Leucocytes
C. Veins
D. Blood capillaries

Explanation

To determine which option does not come under blood vessels, we can analyze each option provided:

1. **Arteries**: Arteries are blood vessels that carry oxygenated blood away from the heart to various parts of the body. They are a crucial part of the circulatory system.

2. **Leukocytes**: Leukocytes, also known as white blood cells, are not blood vessels. They are cells present in the blood that play a key role in the immune system by helping to protect the body against infections and foreign invaders.

3. **Veins**: Veins are blood vessels that carry deoxygenated blood back to the heart. Like arteries, they are an essential component of the circulatory system.

4. **Blood Capillaries**: Blood capillaries are tiny blood vessels that connect arteries and veins. They facilitate the exchange of oxygen, carbon dioxide, nutrients, and waste products between blood and tissues.

From this analysis, we can conclude that the option that does not come under blood vessels is **leukocytes**.

### Step-by-Step Solution:
1. **Identify the options**: The options given are arteries, leukocytes, veins, and blood capillaries.
2. **Define each option**:
- **Arteries**: Blood vessels carrying oxygenated blood.
- **Leukocytes**: White blood cells, part of the immune system, not blood vessels.
- **Veins**: Blood vessels returning deoxygenated blood to the heart.
- **Blood Capillaries**: Small blood vessels for nutrient and gas exchange.
3. **Determine which is not a blood vessel**:
- Arteries, veins, and blood capillaries are all types of blood vessels.
- Leukocytes are cells in the blood, not blood vessels.
4. **Conclusion**: The option that does not come under blood vessels is **leukocytes**.