What is function of cholecystokinin?

Explanation

### Step-by-Step Solution:

1. **Definition of Cholecystokinin (CCK)**: Cholecystokinin is a peptide hormone produced by the mucosal epithelial cells in the duodenum, which is the first part of the small intestine.

2. **Secretion Location**: CCK is secreted by the cells in the duodenum in response to the presence of fats and proteins in the chyme (partially digested food) that enters the small intestine from the stomach.

3. **Role in Digestion**: The primary function of cholecystokinin is to facilitate digestion in the small intestine. It does this by stimulating the release of digestive juices.

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