A patient undergoing duodenal biopsy is found to have complete absence of enteroendocrine I cells. Which digestive function would be MOST impaired?

• A Gastric acid secretion (as CCK normally stimulates parietal cells)
• B Gastric emptying rate (as CCK normally accelerates gastric emptying)
• C Intestinal water absorption (as I cells produce secretin to drive fluid into the gut)
• D Pancreatic enzyme and bile release in response to fat and protein in the duodenum (CCK-mediated) ✓

Explanation

I cells of the duodenum and proximal jejunum secrete cholecystokinin (CCK) in response to fat, protein, and amino acids in the duodenal lumen. CCK stimulates pancreatic acinar cells to secrete digestive enzymes (lipase, proteases, amylase) via CCK-A receptors and causes gallbladder contraction with Oddi's sphincter relaxation to release bile — both essential for fat digestion and absorption. CCK also DELAYS gastric emptying (not accelerates it) and increases gastric acid only indirectly. Secretin (from S cells, not I cells) drives bicarbonate-rich pancreatic fluid.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.