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L45_NPB_101 - Lecture 45 •  SmartSite: – ...

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Unformatted text preview: Lecture 45 •  SmartSite: –  Lecture 45 Notes •  GastrointesCnal System –  Review: Stomach –  Small IntesCnes –  Liver –  Pancreas •  Announcements: –  None •  Reading (Recommended): –  Ch 16 (pg. 588 ­638) 1 Review •  Stomach –  Anatomy & FuncCon: Storage, HCl secreCon, mixing –  MoClity: Filling, Storage, Mixing, Emptying –  SecreCons: Mucous, Chief, Parietal Cells –  Mucosal barrier: Luminal membrane, Tight juncCons, Mucous, 3 ­day cell turnover –  DigesCon: Carbohydrate, Protein –  AbsorpCon: Non ­nutrient only –  Anatomy & MoClity (SegmentaCon & MigraCng moClity complex) –  Ileocecal Valve: transiCon to Large IntesCne 2 •  Small IntesCnes Small IntesCne •  SecreCon –  Juice secreted by small intesCne does not contain any digesCve enzymes –  Synthesized enzymes act within brush ­border membrane of epithelial cells •  Enterokinase •  Disaccharidases •  aminopepCdases 3 Small IntesCne •  DigesCon –  PancreaCc enzymes conCnue carbohydrate and protein –  Brush ­border enzymes complete digesCon of carbohydrates and protein –  Fat is digested enCrely within small intesCne lumen by pancreaCc lipase 4 Small IntesCne •  AbsorpCon –  Absorbs almost everything presented to it –  Most occurs in duodenum and jejunum –  AdaptaCons that increase small intesCne’s surface area •  Inner surface has permanent circular folds •  Microscopic finger ­like projecCons called villi •  Brush border (microvilli) arise from luminal surface of epithelial cells –  Lining is replaced about every three days –  Products of fat digesCon undergo transformaCons that enable them to be passively absorbed •  Eventually enter lymph 5 Large Surface Area of Small IntesCne Fig. 16 ­21, pg. 625 Circular Folds (3x) Villi (10x) Microvilli (20x) = 600x 6 Pancreas •  Mixture of exocrine and endocrine Cssue •  Elongated gland located behind and below the stomach •  Exocrine funcCon –  Secretes pancreaCc juice consisCng of •  PancreaCc enzymes acCvely secreted by acinar cells that form the acini •  Aqueous alkaline soluCon acCvely secreted by duct cells that line pancreaCc ducts •  Endocrine funcCon –  Islets of Langerhans •  Found throughout pancreas •  Secrete insulin and glucagon 7 PancreaCc Enzymes •  Exocrine secreCon is regulated by –  SecreCn –  CCK •  ProteolyCc enzymes –  Digest protein •  Trypsinogen  ­ converted to acCve form trypsin •  Chymotrypsinogen – converted to acCve form chymotrysin •  ProcarboxypepCdase – converted to acCve form carboxypepCdase •  PancreaCc amylase •  PancreaCc lipase –  Converts polysaccharides into the disaccharide amylase –  Only enzyme secreted throughout enCre digesCve system that can digest fat 8 Exocrine Pancreas Fig. 16 ­12, pg. 613 9 Liver •  Largest and most important metabolic organ in the body •  Body’s major biochemical factory •  Importance to digesCve system – secreCon of bile salts 12 Liver •  FuncCons not related to digesCon –  Metabolic processing of the major categories of nutrients –  Detoxifying or degrading body wastes and hormones, drugs, and other foreign compounds –  Synthesizes plasma proteins –  Stores glycogen, fats, iron, copper, and many vitamins –  AcCvates vitamin D –  Removes bacteria and worn ­out red blood cells –  Excretes cholesterol and bilirubin 13 Liver Blood Flow Fig. 16 ­14, pg. 616 14 Hepatocytes Produce Bile SecreCons •  Synthesized de novo from cholesterol… •  Or from recycled bile salts taken up from the hepaCc circulaCon Fig. 16 ­15b, pg. 617 15 Liver •  Bile –  AcCvely secreted by liver and acCvely diverted to gallbladder between meals –  Stored and concentrated in gallbladder –  Consists of •  •  •  •  Bile salts Cholesterol Lecithin Bilirubin •  Bile salts –  Aeer meal, bile enters duodenum –  DerivaCves of cholesterol –  Convert large fat globules into a liquid emulsion –  Aeer parCcipaCon in fat digesCon and absorpCon, most are reabsorbed into the blood 16 Bile Salts Fig. 16 ­17a, pg. 608 17 Bile Salts Stabilize Lipid Droplets Fig. 16 ­17b, pg. 619 18 Micelle Fig. 16 ­18, pg. 620 19 Bile Release and Recycling •  Stored in the gall bladder •  Released into the duodenum •  Almost completely reabsorbed in SI Fig. 16 ­16, pg. 618 20 Fat AbsorpCon Fig. 16 ­26, pg. 630 21 Carbohydrate AbsorpCon Fig. 16 ­24, pg. 627 22 Protein AbsorpCon Fig. 16 ­25, pg. 629 23 Table 16 ­6, pg. 624 24 ...
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