L46_NPB_101 - Lecture 46 •  Online Handouts: • ...

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Unformatted text preview: Lecture 46 •  Online Handouts: •  Announcements: –  Final: •  •  •  •  •  –  Lecture 46 Notes •  Gastrointes:nal System –  Review  ­ Small intes:nes –  Large Intes:nes –  Hormonal Control 60 ques:ons MC 30 ques:ons on Lec 36 ­46 30 ques:ons on Lec 1 ­35 Ques:ons from Lec & Rqd Reading Content ~ propor:onal to Lecs –  Grading will be the higher of either: •  Total % for quarter (M1,M2,F) •  Total % for Final alone •  Reading (Recommended): –  Ch 16 (pg. 588 ­638) 1 Review •  Small Intes:nes –  Luminal structure: circular folds, villi, microvilli •  Increase surface area 600x •  enzymes in brush border –  No diges:ve enzyme secre:on •  Pancreas –  Absorbs almost everything presented to it –  Exocrine Secre:ons: Enzymes & Aqueous alkaline solu:on –  Regulated by hormones and nega:ve feedback loops –  Biochemical balance between stomach, pancreas & small intes:nes –  Diges:ve Secre:ons – Bile (Bile salts, Cholesterol, Lecithin & Bilirubin) –  Convert large fat globules into a liquid emulsion (Fat emulsifica:on) •  Micelle forma:on •  Liver 2 Large Intes:ne •  Primarily a drying and storage organ •  Consists of –  Colon –  Cecum –  Appendix –  Rectum •  Contents received from small intes:ne consists of indiges:ble food residues, unabsorbed biliary components, and remaining fluid •  Colon –  Extracts more water and salt from contents –  Feces – what remains to be eliminated 3 Large Intes:ne •  Taeniae coli •  Haustra –  Longitudinal bands of muscle –  Pouches or sacs –  Ac:vely change loca:on as result of contrac:on of circular smooth muscle layer –  Main mo:lity –  Ini:ated by autonomous rhythmicity of colonic smooth muscle cells 4 •  Haustral contrac:ons Fig. 16 ­28, pg. 635 Large Intes:ne Mo:lity •  Mass movements –  Massive contrac:ons –  Moves colonic contents into distal part of large intes:ne •  Gastrocolic reflex –  Mediated from stomach to colon by gastrin and by autonomic nerves –  Most evident aber first meal of the day –  Oben followed by urge to defecate •  Defeca:on reflex –  Ini:ated when stretch receptors in rectal wall are s:mulated by distension –  Causes internal anal sphincter to relax and rectum and sigmoid colon to contract more vigorously –  If external anal sphincter (skeletal muscle under voluntary control) is also relaxed, defeca:on occurs 5 Table 16 ­7, pg. 633 6 GI Hormones  ­ Gastrin •  Release is s:mulated by presence of protein in stomach •  Secre:on inhibited by accumula:on of acid in stomach •  Acts in several ways to increase secre:on of HCl and pepsinogen •  Enhances gastric mo:lity, s:mulates ileal mo:lity, relaxes ileocecal sphincter, induces mass movements in colon •  Helps maintain well ­developed, func:onally viable diges:ve tract lining (mucosal lining of stomach and small intes:ne) 7 GI Hormones  ­ Secre:n •  Presence of acid in duodenum s:mulates release •  Inhibits gastric emptying in order to prevent further acid from entering duodenum un:l acid already present is neutralized •  Inhibits gastric secre:on to reduce amount of acid being produced •  S:mulates pancrea:c duct cells to produce large volume of aqueous NaHCO3 secre:on •  S:mulates liver to secrete NaCO3 rich bile which assists in neutraliza:on process •  Along with CCK, is trophic to exocrine pancreas 8 Fig. 16 ­13, pg. 615 GI Hormones – Cholecystokinin (CCK) •  Fat and protein in duodenal chyme s:mulates release •  Inhibits gastric mo:lity and secre:on •  S:mulates pancrea:c acinar cells to increase secre:on of pancrea:c enzymes, esp pancrea:c lipase •  Causes contrac:on of gallbladder and relaxa:on of sphincter of Oddi •  Along with secre:n, is trophic to exocrine pancreas •  Implicated in long ­term adap:ve changes in propor:on of pancrea:c enzymes in response to prolonged diet changes •  Important regulator of food intake Fig. 16 ­13, pg. 615 9 ...
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This note was uploaded on 11/07/2010 for the course NPB NPB 101 taught by Professor Weidner/wingfield during the Spring '08 term at UC Davis.

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