Functional units of food absorption are

Options

A. Crypts of Lieberkuhn
B. Peyer's patches
C. Villi
D. Brunner's glands

Answer

### Step-by-Step Text Solution:

1. **Understanding the Question**: The question asks for the functional units of food absorption in the human body.

2. **Identifying Key Structures**: The structures involved in food absorption in the small intestine include:
- Crypts of Lieberkühn
- Peyer's patches
- Villi
- Brunner's glands

3. **Focusing on Villi**: Among these structures, the villi are the primary functional units responsible for nutrient absorption.

4. **Structure of Villi**: Villi are small, finger-like projections that line the small intestine. They significantly increase the surface area available for absorption.

5. **Microvilli**: Each villus is covered with even smaller projections called microvilli. These microvilli further enhance the surface area and contain protein channels that facilitate the absorption process.

6. **Mechanism of Absorption**:
- **Facilitated Diffusion**: Nutrients can pass through the cell membrane of the villi via facilitated diffusion.
- **Active Transport**: Some nutrients require energy to be absorbed, which is provided by ATP produced in the mitochondria present in the epithelial cells of the villi.

7. **Role of Lacteals**: Each villus contains a lacteal, which is a lymphatic vessel that transports absorbed fats away from the intestine.

8. **Conclusion**: Therefore, the correct answer to the question is that the functional units of food absorption are **Villi**.