tunica media will be absent in the Wall of

Options

A. arteries
B. vena cava
C. capillaries
D. veins

Answer

To answer the question about where the tunica media is absent in the wall of blood vessels, we can follow these steps:

### Step 1: Understand the Structure of Blood Vessels
- The blood vessels consist of three main layers:
1. **Tunica intima** (inner layer)
2. **Tunica media** (middle layer)
3. **Tunica adventitia** (outer layer)

### Step 2: Define Tunica Media
- The tunica media is primarily composed of smooth muscle cells and is responsible for regulating the diameter of the blood vessels, which in turn helps control blood flow and blood pressure. It is usually the thickest layer in arteries.

### Step 3: Identify the Types of Blood Vessels
- **Arteries**: Have all three layers, including a well-developed tunica media.
- **Veins**: Also have all three layers, but the tunica media is thinner compared to arteries.
- **Capillaries**: Composed of a single layer of endothelial cells and do not have a tunica media.

### Step 4: Analyze the Options
- Given the options:
1. Artery - has tunica media.
2. Vena cava (a type of vein) - has tunica media.
3. Capillaries - do not have tunica media.

### Step 5: Conclusion
- The tunica media is absent in the walls of capillaries. Therefore, the correct answer is **capillaries**.

### Final Answer
The tunica media will be absent in the wall of **capillaries**.

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