In mammals,surface area of intestine is increased due to presence of

Options

A. Crypts of Lieberkuhn
B. Brunner's glands
C. Villi
D. All of the above

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the structures in mammals that increase the surface area of the intestine. This is important for enhancing the absorption of nutrients.

2. **Identifying Key Structures**: In the intestines, there are several structures that contribute to increasing the surface area. The most significant of these are the villi.

3. **Role of Villi**: Villi are small, finger-like projections that extend into the lumen of the intestine. Their primary function is to increase the surface area available for absorption. The more surface area there is, the more nutrients can be absorbed efficiently.

4. **Other Structures**: While the question mentions other structures such as the crypts of Lieberkühn and Brunner's glands, these do not primarily serve to increase surface area:
- **Crypts of Lieberkühn**: These are gland-like structures that extend from the base of the villi and are involved in secretion and host defense but do not significantly contribute to surface area.
- **Brunner's Glands**: These are found in the duodenum and secrete alkaline fluid to protect the intestinal lining from acidity but are not involved in increasing surface area.

5. **Conclusion**: The presence of villi is the main factor that increases the surface area of the intestine in mammals, facilitating better absorption of nutrients.

**Final Answer**: The surface area of the intestine in mammals is increased due to the presence of villi.

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