Gastric, Intestinal, and Pancreatic Function
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Three functions of the stomach
• Movement of food to the duodenum • Secretion of digestive enzymes, intrinsic factor, and hydrochloric acid • Partial digestion of proteins
Anatomical location of the stomach and names of three distinct zones
• Fundus • Body • Antrum
Specific cell types in each zone of the stomach
Fundus: surface epithelial cells, mucus cells Body: surface epithelial cells, mucus cells, parietal cells Antrum: Mucous cells, G-cells, chief cells
Specific secretion(s) of surface cell epithelial
Produce mucus and shed and proliferate rapidly (every 3 days)
Specific secretion(s) of mucus cells
Secrete mucus
Specific secretion(s) of parietal cells
Hydrochloric acid and Intrinsic Factor
Specific secretion(s) of chief cells
Pepsinogen (that is converted in an acidic environment to pepsin)
Specific secretion(s) of G-cells
gastrin (gastrin stimulates the parietal cells to produce HCL)
Five functions of gastric hydrochloric acid
• Converts pepsinogen to pepsin • Activates rennin (a milk curdling enzyme) • Combines with food proteins to form acid metaproteins which are more easily digested by pepsin • Prevent bacterial multiplication in the stomach • Prevents precipitation of ingested calcium so that soluble calcium may be absorbed
Four stimuli for gastrin release
• When proteins, amino acids and calcium enter stomach • Vagus nerve is activated and releases acetylocholine • Catecholamines are circulating • Antrum is distended
Three phases of gastric secretion
• Cephalic phases • Gastric phase • Intestinal phase
Cephalic phase stimuli and specific secretion produced in each phase
Vagus nerve, stimulated by site and smell, stimulates parietal cells to produce HCL and G-cells to produce gastrin
Gastric phase stimuli and specific secretion produced in each phase
• In the stomach, gastrin release stimulates parietal cells to produce more HCL • Local antral distension stimulates further production of gastrin and therefore HCL • Chief cells respond to acidic environment; pepsinogen is produced that is rapidly converted to pepsin at pH 3 • Chyme is produced (mucus-containing solution)
Intestinal phase stimuli and specific secretion produced in each phase
• Ingested food helps neutralize HCL • Secretin is released, inhibiting gastrin-stimulated acid production and gastric motility • Gastric secretions cease
Three functions of gastric fluid
• Initiation of protein digestion • Physical and chemical preparation of ingested food for absorption • Secretion of intrinsic factor to promote Vit B12 absorption in the ileum
Four normal constituents of gastric secretions
• Hydrochloric acid • Enzymes (pepsin (most important), salivary amylase, gastric lipase) • Mucus • Intrinsic factor
Three abnormal constituents of gastric fluid
• Blood • Food • Organic acids
Appearance of fresh blood in the stomach
red
Appearance of blood that has remained in the stomach for a period of time
old blood is converted to hematin by the acidic pH and has a “coffee grounds” appearance
Four indications for gastric analysis
• Aid in eval of patients with recurrent ulcer disease • Aid in diagnosis of Zollinger-Ellison syndrome by demonstrating a hypersecretory state • Determine if patient is able to secrete HCL at all (pernicious anemia) • Determine the completeness of vagotomy after gastric surgery
Specific diagnostic use of Basal Acid Output (BAO) for gastric function assessment
No stimulation after you fast and you measure if outputting acid; determine baseline pH
Specific diagnostic use of Maximum Acid Output (MAO) for gastric function assessment
Important in determining if the patient has low acidity or anacidity
Specific diagnostic use of Serum gastrin for gastric function assessment
Useful in diagnosis of the Zollinger-Ellison syndrome
Specific diagnostic use of Schilling test for gastric function assessment
Useful in the diagnosis of pernicious anemia