Secretin is gastrointestinal tract hormone that

Options

A. Acts on exocrine part of pancreas and stimulates the secretion of water and bicarbonate ions
B. Acts on exorine part of pancreas and stimulates
C. Acts on gastric galands and stimulates secretion of HCl and pepsinogen
D. Stimulates secretion of gastric lipase from stomach

Answer

**Step-by-Step Solution:**

1. **Understand the Role of Secretin:**
Secretin is a hormone produced in the gastrointestinal tract, specifically in the duodenum, in response to acidic gastric contents entering the small intestine.

2. **Identify the Stimulus for Secretin Release:**
The release of secretin is triggered by the presence of high acidity (low pH) in the duodenum, which occurs when chyme (partially digested food) from the stomach enters the small intestine.

3. **Function of Secretin:**
Once secretin is released, it primarily acts on the exocrine part of the pancreas. The pancreas has both exocrine and endocrine functions, but secretin specifically targets the exocrine glands.

4. **Effects on the Pancreas:**
Secretin stimulates the exocrine pancreas to secrete a bicarbonate-rich fluid. This fluid is important because it helps to neutralize the acidic chyme coming from the stomach, creating a more alkaline environment in the small intestine, which is necessary for the proper functioning of digestive enzymes.

5. **Evaluate the Options:**
- **Option 1:** Correct - Secretin acts on the exocrine part of the pancreas and stimulates the secretion of water and bicarbonate ions.
- **Option 2:** Incorrect - It does not specify what it stimulates.
- **Option 3:** Incorrect - Secretin does not stimulate gastric glands to secrete HCl and pepsinogen.
- **Option 4:** Incorrect - Secretin does not stimulate the secretion of gastric lipase from the stomach.

6. **Conclusion:**
Based on the above analysis, the correct answer is **Option 1**: Secretin acts on the exocrine part of the pancreas and stimulates the secretion of water and bicarbonate ions.

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