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GI Physiology
Gastroenterology
Question | Answer |
---|---|
7 GI layers (outer to inner) | Serosa, longitudinal muscle, Auerbach/myenteric plexus, circular muscle, submucosa (Meissner plexus), mucosa (muscularis mucosa, lamina propria, epithelium) |
MALT (mucosa-associated lymphatic tissue) is in which layer? | Lamina propria |
3 pairs of major salivary glands | Parotid, submandibular, suplingual |
Superficial layer of esophagus is called ___. It is not serosa because ___. | Adventitia. Because its areolar connective tissue is not covered by mesothelium, and bc its connective tissue merges with connective tissue of surrounding structures. |
In the stomach, chief cells secrete (2): | pepsinogen and gastric lipase |
In the stomach, parietal cells produce (2): | intrinsic factor and HCl |
In the stomach, G cells secrete (1): | gastrin |
Function of stellate reticuloendothelial (Kupffer) cells: | Fixed phagocytes that are located in sinusoids: destroy old WBC, RBC, bacteria, other foreign matter in venous blood from GI tract |
In intestine, function of paneth cells (2) | secrete lysozyme; phagocytosis |
Enteroendocrine cells in small intestine (3): | S cells, CCK cells, K cells |
S cells secrete: | secretin |
CCK cells secrete: | CCK (cholecystokinin) |
K cells secrete: | GIP (glucose-dependent insulinotropic peptide) |
Duodenal (Brunner's) glands secrete: | alkaline mucus (neutralizes gastric acid in chyme) |
Fetal development: GI tract first rises in the: | endoderm (forms the primitive gut) |
Fetal development: mesoderm gives rise to (2): | smooth muscle and connective tissue |
Fetal development: ectoderm forms the (2): | stomodeum (oral cavity) and proctodeum |
Cells that form an extensive network of stellate cells in muscle layers of GI tract; associated with smooth muscle cells & enteric neurons = | interstitial cells of Cajal |
Substance that binds to M3-type muscarinic receptors in parietal cells to stimulate H+ secretion = | Acetylcholine |
3 substances that stimulate H+ secretion during feeding | Acetylcholine, gastrin, histamine |
Histamine MOA for H+ secretion | secreted by ECL & mast cells, binds to parietal cell H2 receptors to activate adenylyl cyclase & increase cAMP, which activates protein kinase A to stimulate H+ secretion |
Gastrin is a peptide hormone of (#) or (#) amino acids; somatostatin is a peptide of (#) or (#) amino acids. | Gastrin has 17 or 34. Somatostatin has 14 or 28 |
3 phases of acid secretion during feeding | cephalic phase; gastric phase; intestinal phase |
Protective MOA in stomach's mucous layer for H pylori | Urease converts urea to CO2 and ammonia (latter of which buffers luminal acid & protect H pylori) |
How you get B12 | Dietary B12 binds with haptocorrin, which pancreatic proteases digest in duodenum; in low-acid small intestine, intrinsic factor binds with B12, and complex is taken up by ileum epithelial cells |
Zollinger Ellison syndrome MOA | Recurrent PUD; Gastrinoma increases gastrin production; Gastric acid hypersecretion |
The main vagal mediator that stimulates GI/gastric contraction is: | Acetylcholine |
2 neuronal mediators that inhibit GI/gastric contraction: | VIP and nitric oxide |
Secretin (stimulated by acid) has what effect on gastric contraction? | inhibits antral contraction and stimulates pyloric sphincter contraction to slow gastric emptying |
CCK (stimulated by fat) has what effect on gastric emptying? | acts on vagal nerve receptors to decrease emptying |
The invaginations between small intestinal villi are called: | crypts of Lieberkuhn |
Life span of enterocytes, goblet cells, and enteroendocrine cells (on villi): | 4-6 days |
Life span of Paneth cells: | 60 days |
2 most common phyla of commensal bacteria in intestine | Bacteroides and Firmicutes |
Neurotransmitter secretagogues in the small intestine (2) | VIP and acetylcholine |
Paracrine secretagogues in the small intestine (4) | bradykinin, serotonin, histamine, prostaglandins |
peptide associated with the migrating myoelectric complexes | motilin (22 amino acids) |