LE 40-6Lumen ofstomachMucosa: an epitheliallayer that lines thelumenSubmucosa: a matrix ofconnective tissue thatcontains blood vesselsand nervesMuscularis: consistsmainly of smooth muscletissueSerosa: a thin layer ofconnective and epithelialtissue external to the muscularis0.2 mmLE 41-17EsophagusCardiac orificePyloric sphincterSmallintestineFolds ofepithelialtissueStomachEpitheliumPepsin(active enzyme)PepsinogenHClPepsinogen and HClare secreted into the lumen of the stomach.HCl convertspepsinogen to pepsin.Pepsin then activatesmore pepsinogen,starting a chainreaction. Pepsinbegins the chemicaldigestion of proteins.Parietal cellChief cellChief cellsMucus cellsParietal cellsInterior surface of stomachGastric gland5 µmLE 41-19StomachPancreasLiverGall-bladderDuodenum ofsmall intestineIntestinaljuiceBileAcid chymePancreaticjuiceLE 41-20PancreasLumen of duodenumMembrane-boundenteropeptidaseInactivetrypsinogenOther inactiveproteasesActiveproteasesTrypsinLE 41-21Oral cavity,pharynx,esophagusStomachLumen ofsmall intes-tineSmaller polysac-charides, maltosePolysaccharidesDisaccharidesCarbohydrate digestionSalivary amylasePolysaccharidesPancreatic amylasesMaltose and otherdisaccharidesEpitheliumof smallintestine(brushborder)DisaccharidasesMonosaccharidesProtein digestion Nucleic acid digestionProteinsFat digestionFat globulesDNA, RNAFat dropletsNucleotidesBile saltsPancreatic lipasePancreaticnucleasesNucleotidasesGlycerol, fattyacids, glyceridesNitrogenous bases,sugars, phosphatesNucleosidesNucleosidasesand phosphatasesDipeptidases, carboxy-peptidase, and aminopeptidaseAmino acidsAmino acidsSmall peptidesPancreatic carboxypeptidasePancreatic trypsinand chymotrypsinSmaller polypeptidesPolypeptidesSmall polypeptidesPepsinLE 41-23KeyNutrientabsorptionMicrovilli(brush border)Epithelial cellsLactealLymphvesselVilliLargecircularfoldsEpithelialcellsBloodcapillariesVein carrying bloodto hepatic portalvesselMuscle layersVilliIntestinal wallLE 41-24Fat dropletscoated withbile saltsFat globuleBile saltsMicelles madeup of fatty acids,monoglycerides,and bile saltsEpitheliumof smallintestineEpitheliumof lactealLactealLE
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