Veins have valves which allow blood to flow only in one direction. Arteries do not have valves. Yet the blood flows in one direction only. Can you explain why?

Explanation

### Step-by-Step Solution:

1. **Understanding the Structure of Veins and Arteries**:
- Veins have valves that prevent the backflow of blood, ensuring it flows in one direction towards the heart.
- Arteries, on the other hand, do not have valves.

2. **Function of Valves in Veins**:
- The valves in veins are crucial because they help maintain unidirectional blood flow, especially against gravity, as veins carry blood back to the heart.
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