DigestiveTractGeneralstructureEsophagusStomachSmallintestineLargeintestineEnteroendocrinecellLymphoidtissueandit’simmunityⅠ.GeneralstructureMucosaSubmucosa

MuscularisSerosa1)Epithelium2)LaminaproprialooseCT,Cap,glands,lymphatictissue3)Muscularismucosa:thinsmoothmuscle1.TunicaMucosaDCT,smallA、VandLVsubmucousplexus

glands:esophagus、duodenum2.SubmucosaSilverstainingshowthenerveplexus（1）multipolarneuron（2）unmyelinatednervefibre）

Smoothmuscle:most，innercircularandouterlongitudinalSkeletalmuscle:upperesophagusandanalmyentericplexus

regulatethe

peristalsis3.TunicaMuscularisfibrosa:thinCT

serosa:mesothelium+thinCT4.TunicaAdventitiaTheEsophagus1.Mucosa:nonkeratinnisedstratifiedsqumamousepithelium2.Submucosa:

mucousglands(esophagealglands)3.Muscularis:innercircular,outerlongitudinalupper1/3:skeletalMmiddle1/3:mixedlower1/3:smoothM4.Adventitia:fibrosaesophagealglandscardiafundusbodypylorusStomachIntheemptystate,thestomachiscontractedanditsmucosaandsubmucosaareformingdistinctlongitudinalfoldscalledrugae;whendistendedwithfood,therugaeareflat.SEMpicturesofthestomachsurface(Ⅰ)Mucosa:☆

gastricareagastricpit:3-5gastricglandsopeningsepithelium

laminapropriamuscularismucosa(Ⅱ)Submucosa：LCT、BV、LVet.al(Ⅲ)Muscularis：3layersofsmoothmuscle.(Ⅳ)Adventitia：

serosa1.Epithelium:simplecolumnar

surfacemucouscells

LM:ovoidandbasally-locatednucleistainedpoorlybyHEEM:mucigengranules

tightjunctionsFunction:secreteindissolublemucuswithhighconcentrationofHCO3-

Mucous-HCO3-barrierSelf-protectionmechanismofgastricmucosaHighupdatingrateofthegastricepithelialcellsMucous-HCO3-barrier：Mucus:0.25-0.5mm,indissolublemucousgel,separatetheepitheliumfrompepsinHCO3-:neutralizeH+2.Laminapropria:gastricglands:(1)fundicglands

(2)cardiacglands(3)pyloricglandsCT:fibroblast,lymphocyte,et.al.reticularfiberssmoothM:afew,come

fromMuscularismucosa3.Muscularismucosa：2layersinnercircular,outerlongitudinal3to7fundicglandsopenintothebottomofeachgastricpit.Fundicglands(胃底腺)Location:fundusandbodypartsofthestomachStructure:neckbodybase

Celltypes:

A.

chiefcell

B.parietalcell

C.mucousneckcell

D.endocrinecellE.stemcellChiefcell

orzymogeniccellLM：

BaseandbodyoftheglandsColumnarBase-locatednucleusBasalcytoplasm

basophilicEM：

rERGolgicomplex

Zymogengranules(酶原顆粒)Function：Synthesize

pepsinogen

HCL

pepsinogenpepsinparietalcelloroxynticcellLM：Neck,bodyoftheglandslarge,pyramidal1-2nuclei：centrally-locatedacidophilicEM：1.intracellularsecretorycanaliculus2.tubulovesicularsystem:smoothtubulusandvesicles.

3.Abundanceofmitochondria.Notethatthetubulovescles(TV)inthecytoplasmoftherestingcellfusetoformmicrovilli(MV)thatfilluptheintracellularcanaliculi(IC)Ultrastructuraldifferencesbetweenarestcell(left)andanactivecell(right).Electronmicrographofanactiveparietalcell.Notethemicrovilliprotrudingintotheintracellularcanaliculiandtheabundantmitochondria.Function：1、HCL（hydrochloricacid)：activatepepsinogensterilization(onlyHelicobacterpyloricanlive---involvedinthepathogenesisofgastritisandgastriculcers.)2、Intrinsicfactor：glycoprotein，protect

andbindswithVitB12andaidsitsabsorptioninileum（VitaminB12isacofactorofenzymeswhichsynthesisetetrahydrofolicacid,which,inturn,isneededforthesynthesisofDNAcomponents.AnimpairmentofDNAsynthesiswillaffectrapidlydividingcellpopulations,amongthemthehaematopoieticcellsofthebonemarrow,whichmayresultinperniciousanemia.Thisconditionmayresultfromadestructionofthegastricmucosabye.g.autoimmunegastritisortheresectionoflargepartsofthelowerileum,whichisthemainsiteofvitaminB12absorption,orofthestomach.）pepsinFormationofHClBloodcarbondioxideproducescarbonicacidUndertheactionofcarbonicanhydrase,carbonicaciddissociatesintocarbonateionandHydrogenion

Bicarbonateionistransportedoutofthebasolateralmembraneinexchangeforchlorideion.Chlorideandpotassiumionsaretransportedintothelumenofthecannaliculus

HydrogenionispumpedbyH+/K+-ATPasepumpsintothelumeninexchangeforpotassiumions

MucousneckcellLM：few，neckoftheglands

nucleusflatandbasallylocatedpale-stainedcytoplasmEM：mucigengranule（粘原顆粒）Function：produceacidmucusgastricpitMucousneckcellEndocrinecellAPUD-cells:amineprecursoruptakeanddecarboxylationcells.

G-cell（gastrin-producingcells)：secreteGastrin,accelerateadjacentparietalcelltoproduceHCLD-cell：secretesomatostatin(生長抑素)，decreasethesecretionofparietalcellandotherendocrinecellsStemcelldifficulttobedistinguishedfromothercellsundertheLMmainlylocatedneartheneckoftheglandbutfewinnumber.Thesecellshaveahighrateofmitosis;someofthemmoveupwardtoreplacethepitandsurfacemucouscells.Otherdaughtercellsmigratemoredeeplyintotheglandsanddifferentiateintoothercellsofthegastricgland.Cardiacgland:heavilybranchedtubularglandsmainlymucus-producingcells.

Pyloricgland:Deepgastricpitsmorecoiledthanfundicglands,andmaybebranched.Endocrinecells,inparticulargastrin-producingcells,aremorefrequent.Afewparietalcellsmaybepresentbutchiefcellsareusuallyabsent.Small

intestineTheinnersurfaceofsmallintestinecanbegreatlyenlargedby:*plicaecirculares:madeupof

mucosaand

submucosa.*villi:madeupof

epithelium

and

laminapropria.*microvilli:associatedonlywiththe

epithelium.Plicaecirculares3-fold↓Intestinalvilli10-fold↓Microvilli20-foldIncreasethesurfaceareaasmuchas600-fold,resultinginatotalareaof200m2Jejunum（longitudinal

section）Jejunum（cross

section）SEMpicturesofthesmallintestinesurfaceVilliarefinger-likeorleaf-likeprojectionsofthemucosa.Theyincludeanepithelialcoverandunderlyinglaminapropria.（Ⅰ）mucosa：1.Epithelium☆2.Laminapropria☆3.Muscularismucosa（Ⅱ）submucosa：DCT、BV、LV、duodenalgland(onlyinduodenum)。（Ⅲ）muscularisexterna：soothmuscle,innercircular,outerlongitudinal

（Ⅳ）adventitia:mostlyareserosa

duodenum（cross）Epithelium:Simplecolumnarepithelium1.1Epitheliumofthevilli:composedof3typesofcells.Absorptivecell（吸收細胞）:mostabundantGobletcell：unicellularmucousglands,scattered，secretemucus，lubricate、protectEndocrinecell：scattered,difficulttoidentifyinH&Esections-------describedbelowLM：mostabundant,tallcolumnar,striatedborderEM：

microvilli:2000-3000

cellcoat(glycoprotein):manydigestiveenzymesadheretoit.Disaccharidaseandpeptidases

secretedbyabsorptivecell

pancreaticenzymessER+Golgicomplex：takepartinmetabolismandabsorboffatjunctioncomplex:bindadjacentcellsFunction：absorptionoffats,sugars,andaminoacidsAbsorptivecellMicroviliandcellcoatAbsorptionofprotein

proteinsdigestedintopeptides

-peptidasesboundtothemicrovillidegradepeptidestoaminoacids

-freeaminoacidsabsorbedbyspecifictransporters(Na-dependent)intoabsorptivecellandoutintothecapillary

Absorptionofcarbohydratessimpletubularglandsextendingtomuscularismucosaeandopeningatbaseofvilli.Simplecolumnarepitheliumcontinuouswithvilli:AbsorptivecellGobletcellEndocrinecellPanethcellUndifferentiatedcell

（stemcell）:difficulttoidentifyinH&Esections

1.2Epitheliumformsintestinalglands(Crypts)LM：onlyinthebasesofthesmallintestineglands,typicalfeaturesofprotein-secreting-cellsandacidophilicsecretoryG.EM:rER,Golgicomplex,membrane-coatedG。Function：secretelysozyme,regulatethemicrobialfloraoftheintestinePanethcellPanethcellcrosscutintestinalglandshowingboth:(1)Panethcellswithlarge,red,apicalgranulesand(2)enteroendocrinecellswithsmall,orange-red,basalgranules.2.laminapropria:looseirregularCTcontainingfibroblastsandimmunecells(lymphocytes,plasmacells,mastcells,macrophages,eosinophils)2.1specializationinvilli①centrallacteal→large,blindlymphaticcapillaries;transportchylomicrons

②fenestratedcapillary→transportAAandmonosaccharide③smoothmuscle：orientedalonglongaxisofthevilli,throughcontractiontomovevillus2.2LaminapropriabetweentheintestinalglandsLymphaticnodules：mayevenpenetratethemuscularismucosae.Inileum,thenumberofthemincrease,andcanformaggregatedLymphaticnodulesJejunum:submucosacontainsisolatedlymphoidnodules.Ileum:insubmucosaexisttheaggregated

lymphoidnodulesknownasPeyer’spatches.Villiarefingerlikeshapes.

Microfoldcells

(Mcells)existintheepitheliumprojectionthatcoversthePeyer’spatches,wherenovillusandglandcanbefound.Whatissmallintestinevilli?Anditsstructure?3.muscularismucosa:innercircularandouterlongitudinallayerofsmoothmuscles.(Ⅱ).Submucosa:LCTcontaininglargeblood,lymphvesselsandnerves.(Ⅲ).Muscularis:Innercircularandouterlongitudinallayerofsmoothmuscles.Thenerveplexus(intramuralganglia)existbetweenthe2layers,responsibleforintestinewring.(Ⅳ).:Serousmembrane.Agroupofneuronsandsatellitecellsconstitutingacomponentofthemyenteticpleuxbetweentwosmoothmusclelayers.Duodenum:insubmucosa:isolatedlymphoidnodules.Initssubmucosaexisttheduodenalglandsthatsecretebasicmucus.Villiareleaf-shaped.Fibrousmembraneexistsbehindtheduodenum.Largeintestine-ascendingcolon-transversecolon-descendingcolon-sigmoidcolon-rectum-analcanalColon:AbsenceofplicaeandvilliAnepitheliumcontaininglargenumbersofgobletcellslargeintestinalglandshavenopanethcellsTheouterlongitudinalmuscularis----threethickbandslargeintestinalglandsnumerousGobletcellsAppendix

EnteroendocrinecellsTypePeptidedistributionPBombesinStomach,uppersmallintestineD1VasoativeintestinalpolypeptideAllregionsofGItractECSerotoninAllregionsofGItractEC1SubstancePAllregionsofGItractEC2MolilinDuodenum,ileumECLHistamineSmallintestineGGastrinStomachSSecretinSmallintestineICholecystokinin,pancreozyminSmallintestineD