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Lecture 39
GI Intro-Mouth-Esophagus
Term | Definition |
---|---|
GI Layers | mucose-epithelial cells.submucoas-longitdinal muscle,submucosal plexus.muscularis-circular and longitudinal smooth muscle,myenteric plexus.serosa-outer epithelial layer,produces serosal fluid |
GI Innervation | plexuses-neurons-control local contractions.longitudinal muscle-propulsion of chyme.circular muscle-mixing food and secretions |
Parasympathetic Neurons | active plexus leads to inc GI activity.symp neurons dec GI activity |
Baisc Electrical Rhythm | variable electrical baselines-ca2+ and k+ channels open/close.contraction when BER reaches threshold and AP's occur |
Migrating Motility Complex | strong contraction migrates from stomach to end of SI.starts as previous meal nears complete digestion.clears stomach and SI in anticipation of next meal. |
GI Hormones | released in diff areas.both upstream and downstream effects |
Gastrin | from stomach-proteins strongest stimulus for release. inc stomach secretion of acid and pepsinogen. inc SI ileocecal valve relaxations leads to empties SI.initiates mass movement in LI the triggers defecation |
Cholecystokinin | secreted by duodenum into blood when fat or protein present.causes contraction of gal bladder.causes release of pancreatic digestive enzymes.inhibits stomach secretions. |
Secretin | secreted from duodenum into blood when h+ in duodenum inc secretion of pancreatic digestive enzymes.inhibits stomach secretions |
Mouth | little digestion here.almost no absorp-only some medicine.nitroglycerin absrbed by oral mucosa |
Secretions | bicarbonate neutralizes acids.h2o,amylase,lipase,mucus (to coat food) lysosome-antibacterial enzyme |
Swallowing | Deglutition.boluses formed-coated w/mucus.voluntary propulsion tp pharynx.reflex relaxation off upper esophageal sphincter.bolus forced into esophagus |
Esophagus | tube to stomach-sphincter AT each end.5-9 sec transit time to stomach.no digestion or absorp |
Sphincters | upper e. sphincter relaxes upon swallowing.peristatic contractions behind bolus force it into stomach.lower e.sphincter normally tightly closed-relaxes to let bolus in. |
Reflux | acid into esophagus through LES.loss of neural input most common cause.acid irritates esophagus-heart burn-potential ulcer. |
Gas | in stomach.swallowed gas-some burped out-some absorbed-some to colon.most colonic gas is bacterial |