## Primary Stimulus for CCK Secretion **Key Point:** CCK is secreted by I-cells of the duodenum and proximal jejunum in response to **long-chain fatty acids (>12 carbons) and amino acids/peptides** in the intestinal lumen. ### Mechanism of CCK Release 1. **Fatty acids** — particularly those with chain length >12 carbons are the most potent stimulus 2. **Amino acids and peptides** — released from protein digestion 3. **Weak stimulus** — acidic chyme (pH <3) triggers secretin more than CCK 4. **Not a stimulus** — carbohydrates alone do not trigger significant CCK release ### Functions of CCK | Function | Target Organ | Effect | |----------|--------------|--------| | Gallbladder contraction | Gallbladder | Bile release into duodenum | | Pancreatic enzyme secretion | Pancreas | Increases enzyme-rich secretion | | Sphincter of Oddi relaxation | Sphincter of Oddi | Allows bile and pancreatic juice flow | | Gastric motility inhibition | Stomach | Slows gastric emptying | **High-Yield:** CCK is the most important hormone for **postprandial pancreatic enzyme secretion** and **gallbladder contraction**. Long-chain fatty acids are the strongest stimulus — this is why fatty meals trigger the most vigorous pancreatic and biliary response. **Clinical Pearl:** Patients with fat malabsorption (e.g., pancreatic insufficiency) may have reduced CCK stimulation because fatty acids are not properly digested and absorbed to trigger the hormone's release. [cite:Guyton & Hall 13e Ch 64]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.