Diffusion membrane is made up of which of the following layers

Options

A. Thin squamous epithelium of alveoli
B. Basement membrane
C. Endothelium of alveolar capillaries
D. All of these

Answer

To answer the question, "Diffusion membrane is made up of which of the following layers?", we need to understand the structure of the diffusion membrane involved in the gaseous exchange in the lungs, specifically in the alveoli.

### Step-by-Step Solution:

1. **Identify the Context**: The diffusion membrane is crucial for the exchange of gases (oxygen and carbon dioxide) in the lungs, particularly in the alveoli, which are the air sacs where this exchange occurs.

2. **Understand the Components of the Diffusion Membrane**:
- The diffusion membrane consists of three main layers:
- **Alveolar Epithelium**: This is the thin squamous epithelium that forms the walls of the alveoli. It allows gases to diffuse easily due to its thinness.
- **Basement Membrane**: This layer is found between the alveolar epithelium and the endothelium of the capillaries. It provides structural support and is also thin to facilitate gas exchange.
- **Capillary Endothelium**: This is the layer of cells that line the blood vessels (capillaries) surrounding the alveoli. Like the alveolar epithelium, it is also thin to allow for efficient gas diffusion.

3. **Summarize the Layers**: Therefore, the diffusion membrane is made up of:
- Alveolar epithelium (thin squamous epithelium)
- Basement membrane
- Capillary endothelium

4. **Conclusion**: Since all three layers (alveolar epithelium, basement membrane, and capillary endothelium) are involved in the diffusion process, the correct answer to the question is that the diffusion membrane is made up of all these layers.

### Final Answer:
The diffusion membrane is made up of:
- Alveolar epithelium
- Basement membrane
- Capillary endothelium

### Correct Option:
D. All of these three layers are a part of the diffusion membrane.

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