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Digestive Tracttract Digestive System ——DigestiveDigestive TractTract Dept.Dept. ofof HistologyHistology andand EmbryologyEmbryology 周莉周莉 教授教授 Introduction of digestive system * a long tube extending from the mouth to the anus, and associated with glands. * its main function: -digestion: physical/chemical -absorption * three major sections -the oral cavity including oropharynx -the tubular digestive tract -the major digestive glands: salivary glands, pancreas, liver, the general structure of the digestive tract Ⅰ. General Structure of the Digestive Tract 1. mucosa (1) epithelium: stratified squamous epithelium in two ends, the rest simple columnar epithelium (2) lamina propria: loose connective tissue rich in glands, lymphoid tissue and blood vessel (3) muscularis mucosa: thin layer of smooth muscle cells (innerinner circularcircular andand outerouter longitudinallongitudinal )) 2.2. SubmucosaSubmucosa:: CTCT，， esophagealesophageal glandsglands andand duodenumduodenum glandsglands，， submucosa(Meissnersubmucosa(Meissner)) nervenerve plexusplexus 3.3. muscularismuscularis:: innerinner circularcircular andand outerouter longitudinallongitudinal smoothsmooth musclemuscle cellscells myentericmyenteric nervenerve plexusplexus 4.4. Adventitia:Adventitia: fibrosafibrosa oror serosaserosa Ⅱ. The Oral Cavity 1.1. GeneralGeneral StructureStructure ofof MucosaMucosa ofof OralOral CavityCavity 2.2. tongue:tongue: mucosamucosa andand tonguetongue musclemuscle (( skeletalskeletal muscle)muscle) linguallingual papillaepapillae (1)(1) filiformfiliform papillaepapillae (2)(2) fungiformfungiform papillaepapillae (3)circumvallate(3)circumvallate papillaepapillae lingual papillae Taste Bud tastetaste sensorysensory apparatusapparatus ThreeThree kindskinds ofof cellscells inin HE:HE: darkdark cellscells andand lightlight cellscells (taste(taste cellscells）） basalbasal cellscells Taste bud Ⅲ. Esophagus longitudinallongitudinal plicaplica 1.1. mucosamucosa：：unkeratinizedunkeratinized stratifiedstratified squamoussquamous epitheliumepithelium 2.2. muscularismuscularis mucosa:mucosa: longitudinallongitudinal bunchesbunches ofof smoothsmooth musclemuscle cellscells Esophagus 3.3. SubmucosaSubmucosa:: CT,CT, esophagealesophageal glandsglands andand lymphoidlymphoid tissuetissue inin itit 4.4. muscularismuscularis：： internalinternal circularcircular andand externalexternal longitudinallongitudinal musclemuscle proximalproximal end:end: skeletalskeletal musclemuscle cellscells distaldistal end:end: smoothsmooth musclemuscle cellscells midmid portion:portion: mixturemixture musclemuscle cellscells 5.5. AdvantitiaAdvantitia:: fibrosafibrosa ⅣⅣ StomachStomach gastricgastric area,area, gastricgastric pitspits 1.1. mucosamucosa (1)(1) epitheliumepithelium：： surfacesurface mucousmucous cell:cell: LM:LM: Function:Function: producingproducing mucousmucous withwith – highhigh concentrationconcentration ofof HCOHCO3 (2)(2) laminalamina propriapropria：： fundicfundic glandsglands、、cardiaccardiac glandsglands andand pyloricpyloric glands,glands, gastric pit Stomach FundicFundic glandsglands TheThe organizationorganization：： parietalparietal cellscells ((oxynticoxyntic cells)cells) chiefchief cellscells ((zymogeniczymogenic cells)cells) mucousmucous neckneck cellscells stemstem cellscells endocrineendocrine cellscells ① Parietal Cells So called oxyntic cells LM: see Fig. EM: ① intracellular secretory canaliculus ② microvillus ③ tubulovescular system ④ mitochondria Fundic glands parietal cells (EM) Function: HCl and intrinsic factor For example: ②② ChiefChief cellscells ((zymogeniczymogenic cells)cells) LM:LM: EM:EM: Function:Function: secretingsecreting pepsinogenpepsinogen HClHCl →→ →→ pepsinpepsin RenninRennin Chief cells in EM ③③ NeckNeck mucousmucous cellscells LM:LM: seesee Fig.Fig. Function:Function: secretingsecreting acidicacidic mucousmucous ④④ stemstem cells:cells: ⑤⑤ endocrineendocrine cellscells：：ECLECL cellscells （（secretingsecreting histaminehistamine toto promotepromote producingproducing HClHCl)) DD cellscells （（secretingsecreting somatostatinsomatostatin toto inhibitinhibit parietalparietal cellscells ofof functionfunction）） Cardiac gland：mucous type Pyloric gland：mucous type，more numerous G cells in it secreting gastrin to promote producing HCl Gastric fluid：1.5-2.5L, pH 1.5 - Mucous-HCO3 barrier: undissolved mucingel with large – amount of HCO3 2.2. SubmucosaSubmucosa 3.3. muscularismuscularis：： internalinternal sublayersublayer:: obliqueoblique smoothsmooth musclemuscle cellscells middlemiddle sublayersublayer:: circularcircular smoothsmooth musclemuscle cellscells externalexternal sublayersublayer:: longitudinallongitudinal smoothsmooth musclemuscle cellscells 4.4. advantitiaadvantitia：：serosaserosa Ⅴ. Small Intestine To be divided into three parts: duodenum jejunum ileum Function: *digestion *absorption *secreted certain hormones 1.1. MucosaMucosa circularcircular plicaplica intestinalintestinal villusvillus smallsmall intestinalintestinal glandsglands Small intestine Intestinal villus and small intestinal glands Small intestinal gland 2.2. SubmucosaSubmucosa LCT,LCT, duodenalduodenal glandsglands 3.3. MuscularisMuscularis：：internalinternal circularcircular sublayersublayer andand externalexternal longitudinallongitudinal sublayersublayer smoothsmooth musclemuscle cellscells 4.4. AdvantitiaAdvantitia:: serosaserosa 1. mucosa (1)(1) IntestinalIntestinal villusvillus ①① EpitheliumEpithelium：： simplesimple columnarcolumnar epitheliumepithelium includingincluding absorptiveabsorptive cellscells gobletgoblet cellscells lessless numerousnumerous endocrineendocrine cellscells AAbsorptivebsorptive cellscells：： LM:LM: striatedstriated borderborder EM:EM: microvillus,microvillus, cellcell coat,coat, SERSER andand GolgiGolgi complexcomplex JunctionJunction complexcomplex Function:Function: digestiondigestion absorptionabsorption Villi of small intestine (LM and EM) Absorptive cells (EM) EndocrineEndocrine cells:cells: II cells:cells: cholecystokinincholecystokinin-- pancreozyminpancreozymin ((胆囊收缩素胆囊收缩素--促胰酶素促胰酶素,, CCKCCK--PZPZ )) SS cells:cells: secretinsecretin ((促胰液素促胰液素)) GobletGoblet cells:cells: ②② laminalamina propriapropria:: CT,CT, centralcentral lacteal,lacteal, fenestratedfenestrated capillarycapillary ，，lessless numerousnumerous smoothsmooth musclemuscle cells,cells, lymphocyteslymphocytes，， plasmaplasma cellscells，， macrophagesmacrophages，， eosinophiliceosinophilic cellscells andand mastmast cellscells Lamina propria of intestinal villus (2) small intestinal glands TheThe organizationorganization：： AbsorptiveAbsorptive cellscells GobletGoblet cellscells PanethPaneth cellscells LM:LM: seesee Fig.Fig. function:function: defensindefensin andand lysozymelysozyme EndocrineEndocrine cellscells（（II cellscells SS cellscells）） StemStem cellscells Paneth cells Duodenal glands in submucosa , mucous type，urogastrone(尿抑胃素） SolitarySolitary lymphoidlymphoid nodulesnodules inin submucosasubmucosa ofof jejunumjejunum AggregatedAggregated lymphaticlymphatic nodulesnodules inin submucosasubmucosa ofof ileumileum Ⅵ. Large Intestine 1.1. TheThe coloncolon （（11））mucosamucosa：：PlicaePlicae nono villusvillus，，epitheliumepithelium includingincluding absorptiveabsorptive cellscells andand largelarge numbersnumbers ofof gobletgoblet cellscells LargeLarge intestineintestine glandsglands withwith abundantabundant gobletgoblet cellscells inin laminalamina propriapropria,, stemstem cellscells andand endocrineendocrine cellscells Colon Function:Function: secretingsecreting mucousmucous （（22）） teniatenia colicoli（（ longitudinallongitudinal muscle)muscle) （（33）） advantitiaadvantitia：：fibrosafibrosa,, serosaserosa epiploicaepiploica (( adiposeadipose tissuetissue）） 2. Appendix AA greatgreat abundanceabundance ofof lymphoidlymphoid cellscells andand nodulesnodules inin laminalamina propriapropria,, submucosasubmucosa andand muscularismuscularis mucosamucosa Lymphoid Tissue of Digestive Tract and Immune Function gutgut ––associatedassociated lymphoidlymphoid tissue:tissue: includingincluding lymphoidlymphoid nodulesnodules inin mucosa,mucosa, lymphocytes,lymphocytes, plasmaplasma cellscells andand macrophagesmacrophages inin laminalamina propriapropria andand lymphocyteslymphocytes betweenbetween epithelialepithelial cellscells Function:Function: microfoldmicrofold cells,cells, IgAIgA,, secretorysecretory piece,piece, sIgAsIgA.
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