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GI Secretory Products

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Topic updated on 04/21/14 6:11pm

Overview
Product
Source
Action Regulation Notes
Intrinsic Factor (IF)
  • parietal cells (stomach-body)
  • binds vitamin B12
  • mediates vitamin B12 absorption in terminal ileum
 
  • autoimmune destruction of parietal cells causes (1) chronic gastritis and (2) pernicious anemia
  • gastrectomy results in loss of parietal cells and loss of IF; patient requires B12 injection to prevent pernicious anemia
Gastric Acid (HCl)
  • parietal cells (stomach-body)
  • ↓ stomach pH
  • ↑ by vagal stimulation (ACh), gastrin, histamine
  • ↓ by somatostatin, GIP, prostaglandin, secretin
  • gastrinoma is a gastrin-secreting tumor that causes (1) continuous high levels of HCl secretion and (2) gastric ulcers
Pepsin
  • chief cells (stomach-body)
  • protein digestion
  • ↑ by vagal stimulation (ACh)
  • chief cells secrete inactive pepsinogen, coverted to active pepsin at low pH
HCO3-
  • mucosal cells (stomach, duodenum, salivary glands, pancreas)
  • Brunner's glands (duodenum)
  • acid neutralization
  • ↑ pancreatic secretion by secretin
  • HCO3- is trapped in mucus that covers the gastric epithelium


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