Differentiate between an artery and a vein.

Explanation

### Step-by-Step Solution:

1. **Definition and Function**:
- **Arteries**: Arteries are blood vessels that carry blood away from the heart to various parts of the body. Their primary function is to transport oxygenated blood (except for the pulmonary artery, which carries deoxygenated blood to the lungs).
- **Veins**: Veins are blood vessels that carry blood back to the heart from different body parts. They primarily transport deoxygenated blood (except for the pulmonary vein, which carries oxygenated blood from the lungs to the heart).

2. **Wall Thickness**:
- **Arteries**: The walls of arteries are thick and muscular. This thickness helps them withstand the high pressure of blood being pumped from the heart.
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