消化系统（英文）.ppt

Ch23-DigestiveSystem,Part2,SmallintestinePancreasLiver-HepaticportalsystemGallbladder-BileLargeIntestineChemicaldigestionandabsorption,Junctionofstomachandsmallintestine,SmallIntestine,Majorfunction-responsiblefor90%ofabsorptionandalsoimportantfordigestionDividedintothreeregionsDuodenum-mixingbowlJejunum-chemicaldigestion/absorptionIleum-protectionfromlargeintestine,Layersofthesmallintestine,Plica,Uniquetothesmallintestineisthepresenceofplica(plicaecirculares).Plicaarepermanentfoldsofthemucosaandsubmucosa.,Ontheplica,youwillseevilli-Presentonlyinsmallintestine-Cryptsspacedbetweenthem-Donotconfusewithmircovilli,Oneplica,Onevillus,Plicaandvilli,Eachplicasupportsaforestofvilli.Eachvillusiscoveredwithsimplecolumnarepithelium.Theseepithelialcellshavemicrovilli.Phew!,Villusandenzymesofthebrushbordercells,microvilli,Brushbordercell,Thelaminapropriaofeachvilluscontainsalacteal,nervesandbloodvessels,RegionalFeaturesoftheSmallIntestine,Duodenum-siteofchymeentry,whereitisblastedwithHCO3-(andotherthings)Alongduodenum,pHofchymechangesfrom1-2to7-8MucusglandsofmucosaAlso,Brunnersglands(submucosalglands)Jejunum-firsthalfhasnumerousplicaeandvilli,buttheydecreaseinnumberenroutetoileumBrushborderenzymesIleum-lackplicae,containmassesoflymphoidtissue.why?,Duodenum,Plica,Villi,Crypts,BrunnersGlands(submucosalglands),Jejunum-Panorama,Ileum,Crypts,GobletCells,PeyersPatches,Whatorganssecreteintothesmallintestine?,Gallbladder,Liver,Anatomyofthepancreas,-Anaccessorystructureofthesmallintestine,Pancreas,Wherehaveyouseenthepancreasbefore?Primarilyanexocrinegland(99%ofcells)Composedofaseriesofductulesthataresurroundedbysecretorycells,acinarcells,CuboidalepithelialcellsthatformpancreaticaciniPancreaticjuiceproducedbyacinarcellsAlkalinemixtureofenzymes,water,andionsOver1200mlofjuiceproducedeachday!Travelsinpancreaticduct,joinsthecommonbileduct,AcinarCells,Enzymesproducedbythepancreas,Pancreaticalpha-amylasePancreaticlipaseNucleasesFourinactiveproteolyticenzymesNotactivateduntiltheyreachthesmallintestine,ProteolyticEnzymes,Inactivetrypsinogenconvertedtoactivetrypsinbyenteropeptidase(enterokinase)TrypsinthenconvertsotherproenzymesintotheiractiveformsChymotrypsinCarboxypeptidase,1,2,3,4,trypsinogen,enteropeptidase,Trypsinisnowactive,andwillactivateotherproteases:ChymotrypsinCarboxypeptidase,Brushbordercells,5,6,Inactiveproteaseactiveprotease,Inactiveproteasesreleasedfromacinarcells,trypsin,trypsin,TRYPSIN,Liver,Largestvisceralorgan,3lbSurroundedbyfibrouscapsuleHasnumerouslobes,withnumerouslobulesCellsarecalledhepatocyesReceives25%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,Hepatocytesarrangedintowalls.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,Abigolleakycapillary,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.Eachwavetakes2hours.,Animation-Recap,Thelastpart.largeintestine,GeneralfunctionsReabsorptionofwaterAbsorptionofvitaminsmadebybacteriaCompactionandstorageoffecalmaterial,Anatomyofthelargeintestine,Thelargeintestineiscomprisedofsections:CecumandappendixColon(ascending,transverse,descending,sigmoid)Rectum,leadstoanalcanalandanalcanal,Note-LargediameterThinwalls,HistologyoftheLargeIntestine,Colon-SimplecolumnarwithgobletcellsRectum-theanalcanalisstratifiedsquamousSo,asyoumovefromcolontoout:epitheliumchangesfromcolumnar(withgobletcells)stratifiedsquamouskeratinizedstratifiedsquamous.MucosadoesnotproduceenzymesNovilli,Siteof-Vitamins,bile,andsomeH2Oabsorption,AwordaboutbacterialfloraMostbacteriaareDOA(deadonarrival)atthelargeintestine,butsomesurviveandcomprisethebacterialfloraOver700species!Functions?,ChemicalDigestionandAbsorption,Virtuallyallnutrientsfromthedietareabsorbedintoblood(orlymphvessels)acrossthemucosaofthesmallintestine.Muchofthisabsorptionhappensviaco-transportordiffusionacrosstheapicalmembraneofintestinalepithelialcells(thebrushbordercells),akaeneterocytes,Part1&2Firststepsofmechanicalandchemicaldigestion,Part3Finalstepsofchemicaldigestionandabsorption,Chemicaldigestionandabsorption,Recallpolymersandmonomers,Hydrolysis,HydrolysisisbreakingofabondwithwaterortheadditionofwaterDigestiveenzymeshydrolyzeonespecificsubstrateA-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,withmoleculesmovinginsamedirectionDoesntdirectlyrequireATP,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,FirstwithlipasesBreakd