How many layers are present in the diffusion membrane of alveolar capillary?

Options

A. (1) 5
B. (2) 3
C. (3) 2
D. (4) 4

Answer

To determine how many layers are present in the diffusion membrane of the alveolar capillary, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Function of Alveoli**:
- Alveoli are the primary sites for gas exchange in the lungs. They facilitate the exchange of oxygen and carbon dioxide between the air in the lungs and the blood in the capillaries.

**Hint**: Remember that the alveoli are crucial for respiration and gas exchange.

2. **Identify the Components of the Diffusion Membrane**:
- The diffusion membrane of the alveolar capillary consists of three major components:
- **Thin Squamous Epithelium of Alveoli**: This is the first layer, which is very thin to allow for efficient gas exchange.
- **Endothelium of Alveolar Capillaries**: This is the second layer, which lines the capillaries and is also thin to facilitate diffusion.
- **Basement Membrane**: This is the third layer, which is a thin layer of connective tissue that lies between the epithelium and the endothelium.

**Hint**: Focus on the types of cells and structures involved in the diffusion process.

3. **Count the Layers**:
- By identifying the three components mentioned, we can conclude that there are a total of three layers in the diffusion membrane of the alveolar capillary.

**Hint**: Make sure to list each layer to avoid missing any.

4. **Select the Correct Option**:
- From the options provided (5, 3, 2, 4), the correct answer is **3 layers**.

**Hint**: Cross-reference your count with the options given to confirm your answer.

### Final Answer:
The diffusion membrane of the alveolar capillary consists of **3 layers**.