What regulates the exit of food from stomach into small intestine ?

Options

A. Valve
B. Sphincter muscle
C. Villi
D. All of the above.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the regulation of the exit of food from the stomach into the small intestine.

2. **Identifying the Structure Involved**: The structure that regulates this exit is known as the **pyloric sphincter**.

3. **Function of the Pyloric Sphincter**: The pyloric sphincter is a ring of smooth muscle located at the junction between the stomach and the small intestine. Its primary function is to control the passage of partially digested food (chyme) from the stomach to the small intestine.

4. **Mechanism of Regulation**: The pyloric sphincter opens and closes in response to the digestive process. When the stomach has sufficiently processed the food, the pyloric sphincter relaxes to allow small amounts of chyme to pass into the small intestine. Once the chyme has passed, the sphincter closes to prevent backflow.

5. **Conclusion**: Therefore, the correct answer to the question is that the **pyloric sphincter** (a type of sphincter muscle) regulates the exit of food from the stomach into the small intestine.

### Final Answer:
The pyloric sphincter regulates the exit of food from the stomach into the small intestine.

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