Which of the following facts is the larger lumen of the veins is attributed to

Options

A. tunica media and tunica externa form a single coat
B. tunica interna and tunica media form a single coat
C. tunica interna, tunica media and tunica externa are thin
D. tunica media is a thin coat

Explanation

To solve the question regarding why the larger lumen of veins is attributed to certain structural characteristics, we can break down the explanation into the following steps:

### Step-by-Step Solution:

1. **Understanding the Structure of Veins**:
- Veins are blood vessels that carry blood towards the heart. They have a distinct structure compared to arteries.
- The walls of veins consist of three layers: the tunica externa (outer layer), tunica media (middle layer), and tunica interna (innermost layer).

2. **Comparing Veins and Arteries**:
- The lumen (the inner open space through which blood flows) of veins is larger than that of arteries.
- This difference is primarily due to the thickness of the walls of these vessels.

3. **Role of Tunica Media**:
- The tunica media in veins is thinner than in arteries. It contains fewer muscle fibers.
- In contrast, arteries have a thick tunica media with a higher concentration of muscle fibers, allowing them to withstand higher pressure from the blood pumped by the heart.

4. **Tunica Interna Characteristics**:
- The tunica interna of veins has a simple elastic membrane and a layer of endothelial cells, which contributes to the larger lumen.
- The thinner wall structure of veins allows for a wider lumen compared to arteries.

5. **Conclusion**:
- The larger lumen of veins is attributed to the thinner tunica media and the structural characteristics of the tunica interna.
- Therefore, the correct answer to the question is that the larger lumen of veins is due to the tunica interna and tunica media forming a single coat, which is less muscular compared to arteries.