## Distinguishing CCK vs Secretin Effects on Pancreatic Secretion ### Hormone-Specific Secretory Profiles **Key Point:** CCK and secretin stimulate different components of pancreatic juice, making enzyme vs. bicarbonate content the primary discriminator. | Feature | CCK-Stimulated | Secretin-Stimulated | |---------|---|---| | **Primary stimulus** | Amino acids, fatty acids in duodenum | Acidic chyme (pH < 4.5) in duodenum | | **Enzyme content** | HIGH (amylase, lipase, proteases) | LOW | | **Bicarbonate concentration** | LOW | HIGH (up to 140 mEq/L) | | **Volume of secretion** | Moderate | Large | | **pH of juice** | Neutral to slightly acidic | Alkaline | | **Primary function** | Digestive enzyme delivery | Neutralization of gastric acid | ### Mechanism Basis **High-Yield:** CCK acts primarily on acinar cells → enzyme-rich secretion. Secretin acts primarily on ductal cells → bicarbonate-rich, aqueous secretion. **Clinical Pearl:** In the duodenum, secretin arrives first (pH buffering), followed by CCK (enzyme delivery). This sequential pattern ensures optimal digestion: acid neutralization precedes enzyme action. ### Why This Matters **Mnemonic:** **CCKE** = CCK → Enzymes; **SR** = Secretin → Response (bicarbonate response to acid) The bicarbonate-rich secretin response is essential for: - Neutralizing gastric HCl - Creating optimal pH (7–8) for pancreatic enzymes - Protecting duodenal mucosa from acid damage The enzyme-rich CCK response is essential for: - Protein digestion (proteases) - Fat digestion (lipase) - Carbohydrate digestion (amylase)
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