The main function of interstitial cells is

Options

A. Replacement of lost cells
B. Excretion
C. Digestion
D. Defence

Answer

### Step-by-Step Solution:

1. **Understanding Interstitial Cells**: Begin by recognizing that interstitial cells are specialized cells found in various tissues of the body, including the testes and the intestines.

2. **Identifying Functions**: Interstitial cells have multiple functions depending on their location. In the testes, they are known as Leydig cells and are involved in the production of testosterone, which is crucial for the development of male sexual characteristics.

3. **Role in the Intestine**: In the gastrointestinal tract, interstitial cells are referred to as the interstitial cells of Cajal. These cells play a significant role in the digestive system by regulating peristalsis, which is the wave-like muscle contractions that move food through the digestive tract.

4. **Analyzing Options**: The question provides several options: replacement of lost cells, excretion, digestion, and defense. Based on the functions discussed:
- Replacement of lost cells is not the primary function of interstitial cells.
- Excretion is not directly related to interstitial cells.
- Digestion is a key function of interstitial cells of Cajal in the intestines.
- Defense does not pertain to the role of interstitial cells.

5. **Conclusion**: After analyzing the functions and the options provided, the main function of interstitial cells, particularly in the context of the intestines, is digestion.

### Final Answer:
The main function of interstitial cells is digestion.