Veins are thin walled and have valves. Justify

Explanation

### Step-by-Step Solution:

1. **Understanding the Function of Veins**:
- Veins are blood vessels that carry deoxygenated (impure) blood back to the heart. This is crucial for the circulatory system as it helps in the removal of carbon dioxide and other waste products from the body.

2. **Structure of Veins**:
- Veins have thin walls compared to arteries. The reason for this is that veins operate under lower pressure. The blood in veins is not pumped directly from the heart but rather flows back due to the pressure from the surrounding muscles and the negative pressure created in the thoracic cavity during breathing.

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