Intestinal villi are more numerous and larger in the jejunum than the duodenum because -

Options

A. Digestion is rapid in the posterior part.
B. Absorption is rapid in the later part.
C. More enzymatic activity in the posterior part.
D. More blood supply in the posterior part.

Answer

**Step-by-Step Solution:**

1. **Understanding the Structure of the Small Intestine:**
- The small intestine is divided into three main parts: the duodenum, jejunum, and ileum. Each part has distinct functions related to digestion and absorption.

2. **Function of the Duodenum:**
- The duodenum is primarily responsible for the initial phase of digestion. It receives partially digested food from the stomach along with bile from the liver and digestive enzymes from the pancreas. This is where most of the chemical digestion occurs.

3. **Function of the Jejunum:**
- The jejunum is the middle section of the small intestine and is primarily involved in the absorption of nutrients. It has a larger surface area compared to the duodenum due to the presence of numerous and larger villi.

4. **Role of Villi:**
- Villi are small, finger-like projections that increase the surface area of the intestinal lining, facilitating the absorption of nutrients such as glucose, amino acids, and fatty acids into the bloodstream.

5. **Comparison of Villi in Duodenum and Jejunum:**
- In the jejunum, villi are more numerous and larger compared to those in the duodenum. This is because the jejunum is specialized for absorption, requiring a greater surface area to maximize nutrient uptake.

6. **Reasons for More Villi in Jejunum:**
- The increased number and size of villi in the jejunum can be attributed to:
- **Rapid Absorption:** The jejunum is where the majority of nutrient absorption occurs after digestion in the duodenum.
- **Increased Blood Supply:** The jejunum has a rich blood supply to transport absorbed nutrients efficiently.
- **Enzymatic Activity:** Although enzymatic activity is high in the duodenum, the jejunum has adapted to enhance absorption.

7. **Conclusion:**
- Therefore, the primary reason intestinal villi are more numerous and larger in the jejunum than in the duodenum is due to the rapid absorption of nutrients in the jejunum, necessitating a larger surface area provided by the villi.

**Final Answer:**
Intestinal villi are more numerous and larger in the jejunum than the duodenum because absorption is rapid in the jejunum.

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