...hormone contracts gallbladder to release bile.

Options

A. Gastrin
B. Secretin
C. Enterogastrone
D. Cholecystokinin

Answer

To answer the question regarding which hormone contracts the gallbladder to release bile, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Function of Bile**: Bile is produced by the liver and stored in the gallbladder. It plays a crucial role in the digestion of fats.

2. **Identify the Hormones Mentioned**: The options provided are gastrin, secretin, enterogastron, and cholecystokinin. We need to analyze each of these hormones to determine which one is responsible for contracting the gallbladder.

3. **Analyze Each Hormone**:
- **Gastrin**: This hormone stimulates the secretion of gastric juices in the stomach. It does not have a role in gallbladder contraction. Therefore, it is not the correct answer.
- **Secretin**: This hormone is produced in the duodenum in response to acidic content. It primarily stimulates the pancreas to release bicarbonate to neutralize stomach acid. It does not contract the gallbladder.
- **Enterogastron**: This hormone inhibits gastric movements and works antagonistically to gastrin. It does not contract the gallbladder.
- **Cholecystokinin (CCK)**: This hormone is released in response to the presence of fats and proteins in the small intestine. It stimulates the contraction of the gallbladder, leading to the release of bile into the intestine. Additionally, it also stimulates pancreatic secretions.

4. **Conclusion**: Based on the analysis, the hormone responsible for contracting the gallbladder to release bile is **cholecystokinin**. Therefore, the correct answer is option number 4.

### Final Answer:
**Cholecystokinin (CCK)** is the hormone that contracts the gallbladder to release bile.

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