A vein differ from an artery in having `:-`

Options

A. Strong muscular walls
B. Narrow lumen
C. Valves prevent direction of blood flow opposite to heart
D. Valves prevent direction of blood flow towards heart

Answer

To answer the question "A vein differs from an artery in having:", we need to identify specific characteristics that are unique to veins compared to arteries. Let's break down the solution step by step.

### Step-by-Step Solution:

1. **Function of Veins**:
- Veins carry blood from various parts of the body back to the heart. This is a primary function that distinguishes them from arteries, which carry blood away from the heart.

**Hint**: Remember the direction of blood flow; veins bring blood to the heart, while arteries take it away.

2. **Structure of Veins**:
- The walls of veins are thinner than those of arteries. This is because veins have a thinner tunica media (the middle layer of the blood vessel) which contains fewer muscle fibers.

**Hint**: Think about why veins need thinner walls compared to arteries; consider the pressure of blood flow.

3. **Lumen Size**:
- Veins have a broader lumen compared to arteries. The larger lumen allows veins to hold more blood and accommodate the lower pressure of blood returning to the heart.

**Hint**: Visualize the difference in size; arteries are narrower to withstand higher pressure.

4. **Presence of Valves**:
- Veins contain valves that prevent the backflow of blood, ensuring that it flows in one direction towards the heart. This is a key feature that arteries do not have.

**Hint**: Think about how valves function in a system; they ensure unidirectional flow.

5. **Blood Flow Speed**:
- The flow of blood in veins is slower compared to arteries. This is due to the lower pressure in veins and the larger lumen.

**Hint**: Consider how pressure affects flow speed; higher pressure means faster flow.

6. **Oxygenation of Blood**:
- Most veins carry deoxygenated blood back to the heart, except for the pulmonary veins, which carry oxygenated blood from the lungs to the heart.

**Hint**: Remember the role of the pulmonary veins in the circulatory system.

### Conclusion:
Based on the above characteristics, we can conclude that veins differ from arteries in having valves that prevent the backflow of blood. This is the most distinguishing feature.

### Final Answer:
Veins differ from arteries in having valves that prevent the backflow of blood.