20. GI secretory products Flashcards
Intrinsic factor - source
Parietal cells
stomach
Intrinsic factor - action
Vitamin B12–binding
protein (required for B12
uptake in terminal ileum)
Autoimmune destruction
of parietal cells –>
chronic
gastritis and pernicious
anemia.
Gastric acid -SOURCE
Parietal cells
stomach
Gastric acid - ACTION
dECREASED stomach pH
Gastric acid - REGULATION
INCREASED by histamine, ACh, gastrin DECREASED by somatostatin, GIP, prostaglandin, secretin
Pepsin -SOURCE
Chief cells
stomach
Pepsin - ACTION
Protein digestion
Pepsin - REGULATION
increased by vagal
stimulation,
local acid
Pepsinogen (inactive) is
converted to
pepsin (active) in
the presence of H+.
Bicarbonate trapped in
Trapped in mucus that covers
the gastric epithelium.
Bicarbonate -SOURCE
Mucosal cells (stomach, duodenum, salivary glands, pancreas) and Brunner glands (duodenum)
Bicarbonate - ACTION
Neutralizes acid
Bicarbonate -REGULATION
INCREASED by pancreatic
and biliary
secretion with
secretin
• In pernicious anemia, destruction of gastric ____ cells leads to deficiency of ____ required for vitamin B12 uptake in the ____.
Parietal; intrinsic factor; terminal ileum
• A patient has chronic abdominal pain and numerous peptic ulcers refractory to proton pump inhibitors. What tumor should be suspected?
Gastrinoma, which is a gastrin-secreting tumor that results in high levels of acid secretion
• Describe how pepsin is activated.
It is activated by vagal stimulation of increased acid output, which cleaves inactive pepsinogen to active pepsin
• What is the primary role of pepsin? What cells secrete it, and where are these cells found?
Functions in protein digestion; secreted by the gastric chief cells
• Bicarbonate is secreted by ____ cells and ____ glands; its function is to ____ acid.
Mucosal; Brunner; neutralize
• A patient with a gastrinoma can be expected to also have excessive activation of which pro-enzyme?
Pepsinogen (activated by acid, the release of which is stimulated by gastrin)
• Produced by these cells found in this organ, pepsinogen becomes pepsin when there is a high acid content in the stomach.
Chief cells of the stomach
• Increased levels of what three molecules cause parietal cells to release gastric acid?
Acetylcholine, histamine, and gastrin
• Decreased levels of which hormones will cause parietal cells to secrete gastric acid?
Somatostatin, GIP, prostaglandin, secretin
• Increased secretin levels increase the secretion of this molecule, whose main purpose is to neutralize acid.
Bicarbonate
• Where is bicarbonate typically trapped in the GI system?
Bicarbonate is trapped in the mucus that covers the gastric epithelium
• A patient has vitamin B12 deficiency. What part of the GI system could be damaged, impacting vitamin B12 levels?
Parietal cells of the stomach or the terminal ileum (the latter is where vitamin B12 is absorbed as a complex with intrinsic factor)
• Where are bicarbonate-secreting mucous glands found? What about bicarbonate-secreting Brunner glands?
Stomach, duodenum, salivary glands, pancreas; duodenum
