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372 seCtion iii Gastrointestinal ` gastrointestinal—PHysiology Gastrointestinal ` gastrointestinal—PHysiology

Gastrointestinal secretory products
ProDUCt soUrCe aCtion regUlation notes
Intrinsic factor Parietal cells Vitamin B –binding Autoimmune destruction
12
(stomach A ) protein (required for B of parietal cells Ž chronic
12
uptake in terminal ileum) gastritis and pernicious
anemia.
Gastric acid Parietal cells  stomach pH  by histamine,
(stomach) vagal
stimulation
(ACh), gastrin
 by somatostatin,
GIP,
prostaglandin,
secretin
Pepsin Chief cells Protein digestion  by vagal Pepsinogen (inactive) is
(stomach) stimulation converted to pepsin (active) in
(ACh), local the presence of H .
+
acid
Bicarbonate Mucosal cells Neutralizes acid  by pancreatic Trapped in mucus that covers
(stomach, and biliary the gastric epithelium.
duodenum, secretion with
salivary glands, secretin
pancreas) and
Brunner glands
(duodenum)

A
Gastric pit
Surface epithelium
Upper glandular Mucous cell
layer Parietal cell
Deeper glandular Chief cell
layer
Enterochroma n-like
Muscularis mucosa cell
Submucosa

FAS1_2019_09-Gastrointestinal.indd 372 11/7/19 4:42 PM