Secretin is released from S-cells of the duodenum. Its primary physiological role in digestion is:

• A Stimulating pancreatic ductal cells to secrete a bicarbonate-rich fluid to neutralise duodenal acid ✓
• B Stimulating pancreatic acinar cells to secrete digestive enzymes
• C Contracting the gallbladder to release bile into the duodenum
• D Stimulating gastric parietal cells to secrete HCl

Explanation

Secretin is released by S-cells in the duodenal mucosa in response to duodenal acidification (pH <4.5). It acts on pancreatic ductal (centroacinar) cells via cAMP-mediated mechanisms to produce a large volume of HCO3--rich fluid. This bicarbonate neutralises the acidic chyme entering the duodenum, creating an optimal pH (~7) for pancreatic enzyme function. Cholecystokinin (CCK) stimulates pancreatic enzyme secretion and gallbladder contraction. Gastrin stimulates parietal cell HCl secretion. Secretin actually inhibits gastric acid secretion (enterogastrone effect).

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.