消化系统（英文）.ppt

Ch23 DigestiveSystem Part2 SmallintestinePancreasLiver HepaticportalsystemGallbladder BileLargeIntestineChemicaldigestionandabsorption Junctionofstomachandsmallintestine SmallIntestine Majorfunction responsiblefor90 ofabsorptionandalsoimportantfordigestionDividedintothreeregionsDuodenum mixingbowl Jejunum chemicaldigestion absorptionIleum protectionfromlargeintestine Layersofthesmallintestine Plica Uniquetothesmallintestineisthepresenceofplica plicaecirculares Plicaarepermanentfoldsofthemucosaandsubmucosa Ontheplica youwillseevilli Presentonlyinsmallintestine Cryptsspacedbetweenthem Donotconfusewith mircovilli Oneplica Onevillus Plicaandvilli Eachplicasupportsaforestofvilli Eachvillusiscoveredwithsimplecolumnarepithelium Theseepithelialcellshavemicrovilli Phew Villusandenzymesofthebrushbordercells microvilli Brushbordercell Thelaminapropriaofeachvilluscontainsalacteal nervesandbloodvessels RegionalFeaturesoftheSmallIntestine Duodenum siteofchymeentry whereitisblastedwithHCO3 andotherthings Alongduodenum pHofchymechangesfrom1 2to7 8MucusglandsofmucosaAlso Brunner sglands submucosalglands Jejunum firsthalfhasnumerousplicaeandvilli buttheydecreaseinnumberenroutetoileumBrushborderenzymesIleum lackplicae containmassesoflymphoidtissue why Duodenum Plica Villi Crypts Brunner sGlands submucosalglands Jejunum Panorama Ileum Crypts GobletCells Peyer sPatches Whatorganssecreteintothesmallintestine Gallbladder Liver Anatomyofthepancreas Anaccessorystructureofthesmallintestine Pancreas Wherehaveyouseenthepancreasbefore Primarilyanexocrinegland 99 ofcells Composedofaseriesofductulesthataresurroundedbysecretorycells acinarcells CuboidalepithelialcellsthatformpancreaticaciniPancreaticjuiceproducedbyacinarcellsAlkalinemixtureofenzymes water andionsOver1200mlof juice producedeachday Travelsinpancreaticduct joinsthecommonbileduct AcinarCells Enzymesproducedbythepancreas Pancreaticalpha amylasePancreaticlipaseNucleasesFourinactiveproteolyticenzymesNotactivateduntiltheyreachthesmallintestine ProteolyticEnzymes Inactivetrypsinogenconvertedtoactivetrypsinbyenteropeptidase enterokinase TrypsinthenconvertsotherproenzymesintotheiractiveformsChymotrypsinCarboxypeptidase 1 2 3 4 trypsinogen enteropeptidase Trypsinisnowactive andwillactivateotherproteases ChymotrypsinCarboxypeptidase Brushbordercells 5 6 Inactiveprotease activeprotease Inactiveproteasesreleasedfromacinarcells trypsin trypsin TRYPSIN Liver Largestvisceralorgan 3lbSurroundedbyfibrouscapsuleHasnumerouslobes withnumerouslobulesCellsarecalledhepatocyesReceives 25 oftotalcardiacoutput Bloodflowtoandfromtheliverisunique HepaticPortalSystem Liverreceives1 3ofbloodviahepaticartery notshown 2 3fromhepaticportalveinThismajorveindrainscapillariesfrom esophagus stomach smallandlargeintestineandTHENheadstoliverVenousbloodfromliverdumpsdirectlyintoinferiorvenacava Anyguessesastoamajorfunctionoftheliver HepaticPortalSystem TheportalvenousbloodcontainsalloftheproductsofdigestionabsorbedfromtheGItract Thusallnutrientsareprocessed viewedintheliver byhepatocytes beforebeingreleasedbackintothecentralveins Liver EachlobedividedintolobulesCellsoftheliverarehepatocytesArrangedasasinglelayerofcells stackedDividedbysinusoidsBloodflowsthroughsinusoids pastKupffercells residentmacrophage bacteria Liverlobules Hepatocytesarrangedinto walls Wallsradiateoutwardfromacentralpoint Thecentralareacontainsasingle centralvein Bloodisflowingtowardscenter Liverlobules PortalTriads CentralVein PortalTriad Majorfunctionsoftheliver MetabolicregulationHematologicalregulationBileproduction itsonlytruedigestivefunction MetabolicRegulation HepatocytesregulatethecompositionofthebloodandbloodnutrientsTheydothisbyselectivelysecretingandabsorbingmoleculesfromthebloodWhatmolecules Carbs lipids aminoacids wasteproducts vitamins mineralsanddrugs Portaltriad Metabolicregulation HepatocytesadjustthecontentsofthebloodbyselectiveabsorptionandsecretionRemove storeexcessnutrientsCorrectdeficienciesHepatocytesareabletotakeinand orreleaselargemoleculeswithease partlybecausethenearbycapillariesaresoleaky hepatocytes Abigol leakycapillary asinusoidalcapillary Whatroledoestheliverplayinaminoacidmetabolism RemovesexcessaminoacidsfromthebloodstreamorreleasesstoredaminoacidsthataredeficientBesidesmaintenance growth whatmighttheseaminoacidsbeusedfor Alanine valine leucine proline etc etc Whatroledoestheliverplayinlipidmetabolism Regulatescirculatinglevelsoftriglycerides fattyacids andcholesterolIflevelsdecline lipidstoresarebrokendownandreleasedALSO wewillreturntoBilein3minutes animportantplayerinlipidbreakdown Whatroledoestheliverplayincarbohydratemetabolism Bloodglucoselevelsarekeptatornear90mg dlIfbloodglucoselevelsrise glucoseisstoredinliveras Ifglucoselevelsdrop glycogenreservesintheliverarebrokendownandglucoseisreleasedintoblood Othermetabolicfunctionsoftheliver RemovalofwasteproductsAmmoniaisconvertedtoureaVitaminstorageThefatsolubleones MineralstorageDruginactivation Hematologicalregulation Synthesisofplasmaproteins thinkalbumins etc Removalofhormones likeagiantsponge thelivertakesNE epi thyroidhormones steroidhormones etc outofthegame RemovalofantibodiesRemoval orstorage oftoxinsPhagocytosis KupffercellschompupRBCsandareAPCs Productionofbile 1liter day Hepatocytesproducebile BileismadeandthensecretedintochannelscalledbilecanaliculiCanaliculimergetojointhebileductsateachofthetriads triad Whatisbile Bileisanalkalinesolutioncontaining water electrolytes bilirubin phospholipids triglycerides cholesterol andlipidsknownasbilesaltsFunctionofbile bilesalts emulsifyfatsfordigestionBilesaltsarenotenzymes theymerelyhelptobustuplargefatdropletsintosmallerfatdroplets Whyisthisimportant GallBladder Majorfunctions BilestorageBileconcentration modification Gallbladderreceivesbilefromliverviathecysticduct Whatregulatesreleaseofbile Whenchymeentersthesmallintestine CCKisreleasedCCKrelaxessphincter sphincterofOddi andtriggersmusclecontractionsthatsqueezethegallbladderandsendbileout intoduodenumHowcleverthatCCKsecretionincreaseswhenchymeishighinfats Interestingnote CCKalsoslowsstomachmovement releaseoffoodtoduodenum Whatdoesthistellyouaboutahighfatmeal ReviewofDigestionatSmallIntestine ChymeentersduodenumfromstomachGetsblastedwithHCO3 enzymesandbileWhichenzymes Wherefrom Areallenzymesactiveuponarrival Whichonesare Whichonesarenot SegmentationprovidesmechanicaldigestionBilesaltssurroundfats increasinglipaseeffectivenessABSORBPTIONofnutrients Oncemostabsorptiondone twowavesofperistalsispushleft oversintolargeintestines Eachwavetakes 2hours Animation Recap Thelastpart largeintestine GeneralfunctionsReabsorptionofwaterAbsorptionofvitaminsmadebybacteriaCompactionandstorageoffecalmaterial Anatomyofthelargeintestine Thelargeintestineiscomprisedofsections CecumandappendixColon ascending transverse descending sigmoid Rectum leadstoanalcanalandanalcanal Note LargediameterThinwalls HistologyoftheLargeIntestine Colon SimplecolumnarwithgobletcellsRectum theanalcanalisstratifiedsquamousSo asyoumovefromcolontoout epitheliumchangesfromcolumnar withgobletcells stratifiedsquamous keratinizedstratifiedsquamous MucosadoesnotproduceenzymesNovilli Siteof Vitamins bile andsomeH2Oabsorption AwordaboutbacterialfloraMostbacteriaareDOA deadonarrival atthelargeintestine butsomesurviveandcomprisethebacterialfloraOver700species Functions ChemicalDigestionandAbsorption Virtuallyallnutrientsfromthedietareabsorbedintoblood orlymphvessels acrossthemucosaofthesmallintestine Muchofthisabsorptionhappensviaco transportordiffusionacrosstheapicalmembraneofintestinalepithelialcells thebrushbordercells akaeneterocytes Part1 2Firststepsofmechanicalandchemicaldigestion Part3Finalstepsofchemicaldigestionandabsorption Chemicaldigestionandabsorption Recallpolymersandmonomers Hydrolysis Hydrolysisisbreakingofabond withwater ortheadditionofwaterDigestiveenzymeshydrolyzeonespecificsubstrateA B C D H2OA B H OH C D ABCDase Absorption Carbohydrates simple hexosesugarswillbeabsorbedProteins diortripeptidesaretypicallyabsorbed alsoaminoacidsFats Fattyacidsandmonoglyceridesareabsorbed andthenconvertedimmediatelybacktotriglycerides Carbohydrates Sucrasecatalyzesthecleavageofthebondbetween glucose fructose insucroseLactasecatalyzesthecleavageofthebondbetween glucose galactose inlactoseMaltasecatalyzesthecleavageofthebondbetween glucose glucose inmaltose Wheredowefindthesethreeenzymes Enzymesaretransmembrane oratleastmembrane associated proteinsFunctionatthemicrovilliofenterocytes brushbordercells Apicalsurface brushbordercells Sucrase Maltase Lactase Disaccharidesinintestinallumeninteractwithbrushborderenzymes andtheenzymaticproductsareabsorbed brushbordercells Sucrase Maltase Lactase Sucrose Maltose Lactose Hexosesugars Hexosesugars Hexosesugars Whenbrushborderepithelialcellsfailtomakelactase Lactoseisnotdigestedorabsorbed BacteriafermentlactoseGas diarrhea etc Sucrase Maltase Lactase AbsorptionofCarbs Monosaccharides glucoseandgalactose areintoepithelialcellmembranesviacotransport alongwithNa FructosemovesinviafacilitateddiffusionAllmonosacs passthroughbasalmembraneofcell towardcapillary byfacilitateddiffusion Co transport AspecialtypeofpassivetransportMovesmorethanonemoleculeatsametime withmoleculesmovinginsamedirectionDoesn tdirectlyrequireATP butcellexpendsATPtomaintainhomeostasisCotransportcanfunctiondespiteanopposingconcentrationgradientExample glucose Na co transporter LUMEN Capillary Lacteal Absorbednutrientscanenteracapillaryoralacteal Sucrose Maltose Hexosesugars Carbsandpeptidesentercapillaries Fatsenterlacteals Animation absorption ProteinDigestion Effectsofmastication mechanicaldigestion EffectsofpHonproteinstructureWhatenzymesarefirstinvolved Wherearetheyfound Whatenzymesareatbrushborder Atbrushborder trypsinogenisconvertedtotrypsinbyenterokinaseTrypsinthenactivates chymotrypsin elastaseandcarboxypepsidaseDipeptidasesatbrushborder trypsinogentrypsin enterokinase Trypsinactivatespancreaticproteases Dipeptidasesaremembraneenzymes Dipeptidases Activatespancreaticpeptidases Absorptionofproteins AminoacidsareabsorbedbyFacilitateddiffusionCotransportOnceinsidethecelltheytransportedoutvia Facilitateddiffusion diffusion Hepaticportal Digestionoflipids Whatenzymesareinvolved Wherearetheyfound LipidDigestionandAbsorption FirstwithlipasesBreakdow