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

### Step-by-Step Solution:

1. **Understanding the Diffusion Membrane**: The diffusion membrane is a crucial structure in the respiratory system where gas exchange occurs. It is composed of multiple layers that facilitate the movement of gases (oxygen and carbon dioxide) between the alveoli and the blood.

2. **Identifying the Layers**:
- **Thin Squamous Epithelium of Alveoli**: This is the innermost layer of the diffusion membrane. It is made up of thin, flat cells that allow for easy diffusion of gases.
- **Basement Membrane**: This layer lies beneath the squamous epithelium. It provides structural support and anchors the epithelium to the underlying tissues.
- **Endothelium of Alveolar Capillaries**: This is the outermost layer of the diffusion membrane. It consists of the endothelial cells lining the capillaries, which are also thin to facilitate gas exchange.

3. **Analyzing the Options**:
- The options provided are:
- A) Thin squamous epithelium of alveoli
- B) Basement membrane
- C) Endothelium of alveolar capillaries
- D) All of these
- Since all three components (squamous epithelium, basement membrane, and endothelium) are part of the diffusion membrane, the correct answer is option D) All of these.

4. **Conclusion**: The diffusion membrane is made up of the thin squamous epithelium of alveoli, the basement membrane, and the endothelium of alveolar capillaries. Therefore, the answer to the question is "all of these."