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28 Cards in this Set
- Front
- Back
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What are 4 acid-related GI diseases?
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GERD, PUD (peptic ulcer disease), NSAID-induced ulcers, Stress-related ulcerations
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What are the 4 GI Agents available?
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Drugs for acid disease (antisecretory agents to reduce gastric acid, cytoprotective agents, antacids), Drugs for GI motility (Prokinetic agents), Drugs for N/V, Antidiarrheals
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GI Physiology: The cardia near fundus has mucus producing cells. What about the body & antrum?
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The body contains parietal and chief cells. The parietal cells secrete acid and intrinsic factor. The chief cells secrete pepsinogen. The antrum contains G cells, which secrete gastrin
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What are the 3 main factors in acid stimulation?
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Neuronal, Endocrine and Paracrine
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What does neuronal stimulation produce?
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Acetylcholine (ACh)
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What does endocrine stimulation produce?
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Gastrin
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What does paracrine stimulation produce?
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Histamine
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What are the 5 types of secretory cells in the stomach?
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Parietal cells, ECL, G cells, Superficial epithelial cells, D cells
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What do the Parietal cells in the body & fundus secrete?
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H+
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What do the ECL (EnteroChromaffin-Like) cells secrete?
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Histamine
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What do the G cells in the antrum secrete?
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Gastrin, which in turn triggers the release of histamine.
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What do the Superficial epithelial cells secrete?
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Bicarb (HCO3-) and mucus
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What do the D cells in the antrum secrete?
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Somatostatin, which inhibits gastrin secretion
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The activation of HCl secretion relies on a combination of neurocrine - endocrine and paracrine events. What 2 types of drugs can we use to block the secretion of HCl?
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H-2 receptor blockers and H/K ATPase pump inhibitors
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What are the 2 phases of gastric secretion?
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The cephalic phase, which is initiated by the brain (vagus nerve to the medulla oblongata). The gastric phase, initiated by gastric, or physical/food in stomach events.
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GI innervation and motility is controlled by what 2 systems?
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The parasympathetic and sympathetic. They balance each other out. The parasympathetic helps the digestive process (rest & digest), and the sympathetic inhibits the digestive process.
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GI structure and function serve what 2 types of movement?
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Propulsion and mixing
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What something is eaten and swallowed the esophagus utilizes a peristaltic wave action to get the food down to the:
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lower esophageal sphincter (LES), which is normally constricted until it catches the wave and relaxes to allow passage of food.
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The LES constricts again to protect the lower esophagus and “traps the food” before it enters the stomach. In the stomach:
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peristaltic contractions move and mix food with gastric secretions.
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The pyloric sphincter maintains constant tonic constriction and allows water/fluid to pass constantly to the duodenum (?) Gastric emptying is the time & process required to empty the stomach. What regulates it?
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Signals from the stomach and duodenum. It also depends on what you ate - fat takes longer to pass.
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HCl (hydrochloric acid) is secreted by the parietal cells which first need to be stimulated by:
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ACh, gastrin and histamine.
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Pepsinogen is secreted from peptic and mucous cells. ONLY in the presence of:
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HCl does pepsinogen convert to pepsin. Pepsin is the problem. It’s irritating, and only forms in the presence of pepsinogen and HCl. In an acidic pH it’s now a proteolytic enzyme.
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What is feedback inhibition?
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The gastric pH increases (becomes more basic) during the digestive process. Feedback inhibition occurs when pH reaches 3-4 (HCl is 1-2 pH)
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What 4 physiological properties does the GI tract have as intrinsic protection?
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Mucous/bicarb. Gastric blood flow. Cell turnover. Prostaglandin E2.
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How does mucous and bicarb offer intrinsic protection?
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Mucous provides a barrier, and the bicarb neutralizes acid.
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How does gastric blood flow offer intrinsic protection?
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It pulls acid away and into the bloodstream, where its neutralized quickly.
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How does cell turnover offer intrinsic protection?
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there’s continuous cellular replacement. (This is not the case with patients on chemo - they have reduced cell turnover)
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How does Prostaglandin E2 offer intrinsic protection?
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It’s a protective prostaglandin, secreted by mucosal cells when the pH is less than 3. It inhibits acid secretion.
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