This epithelium is made up of a single thin layer of flattened cells and is involved in diffusion, it is found in : -

Options

A. Walls of blood vessels
B. Ducts of glands
C. Tubular parts of nephrons
D. All of these

Answer

To answer the question regarding the epithelium made up of a single thin layer of flattened cells involved in diffusion, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Characteristics of the Epithelium**:
- The epithelium in question is described as a single layer of flattened cells. This type of epithelium is known as simple squamous epithelium.

2. **Identify the Function of the Epithelium**:
- The primary function of simple squamous epithelium is diffusion. This means it facilitates the movement of substances (like gases) across its surface.

3. **Consider Where This Epithelium is Found**:
- Simple squamous epithelium is commonly found in areas where diffusion is crucial. Notable locations include:
- The walls of blood vessels (particularly capillaries)
- The alveoli of the lungs
- The lining of body cavities (serous membranes)

4. **Evaluate the Options Provided**:
- If the options include:
- Walls of blood vessels
- Alveoli
- Ducts of glands
- Tubular parts of the nephron
- We can analyze each option:
- **Walls of blood vessels**: This is correct as capillaries consist of simple squamous epithelium.
- **Alveoli**: This is also correct as the alveoli are lined with simple squamous epithelium for efficient gas exchange.
- **Ducts of glands**: This is generally not correct as they are lined with cuboidal or columnar epithelium.
- **Tubular parts of the nephron**: While they do have a simple epithelium, it is not specifically the flattened type involved in diffusion.

5. **Conclusion**:
- The correct locations for the simple squamous epithelium involved in diffusion are the walls of blood vessels and the alveoli. Therefore, the best answer to the question is that this epithelium is found in the **walls of blood vessels and alveoli**.