Download - Digestive system part 2
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aboutabout 2525--cmcm--long long muscularmuscular tubetube
functionfunction: : forwardingforwarding swallowedswallowed foodfood fromfromthethe pharynxpharynx downdown intointo thethe stomachstomach
itsits lumen is lumen is starstar--shapedshaped, , duedue toto thethelongitudinallongitudinal reservereserve foldsfolds
thethe typicaltypical structurestructure ofof thethe alimentaryalimentary canalcanalappearsappears inin thisthis segmentsegment
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epitheliumepithelium ((laminalamina epithelialisepithelialis mucosaemucosae):):stratifiedstratified, , nonkeratinizednonkeratinized squamoussquamousepitheliumepithelium atat itsits entireentire lengthlengthlaminalamina propriapropria mucosaemucosae comprisescomprises cardiaccardiacesophagealesophageal glandsglands ((glandulaeglandulae oesophageaeoesophageaecardiacaecardiacae) ) inin itsits beginingbegining andand terminalterminalportionsportions; ; thesethese glandsglands resembleresemble thethe cardiaccardiacglandsglands, hence , hence thethe namename
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cardiaccardiac esophagealesophageal glandsglands produceproduce neutralneutral mucin, mucin, whichwhich protectsprotects thethe cellscells againstagainst thethe possiblepossible refluxrefluxofof gastricgastric juicejuiceinin thethe laminalamina propriapropria, , therethere areare scatteredscattered lymphaticlymphaticelementselements, , frequentlyfrequently inin thethe vicinityvicinity ofof thethe excretoryexcretoryductsductslaminalamina muscularismuscularis mucosaemucosae is is composedcomposed ofof mainlymainlylongitudinallongitudinal smoothsmooth musclemuscle cellscells
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is is thrownthrown intointo longitodinallongitodinal foldsfolds, , justjust likelikemucousmucous membranemembranetherethere areare mixedmixed oror purelypurely mucousmucous smallsmallsalivarysalivary glandsglands, , whichwhich areare calledcalled esophagealesophagealglandsglands properproper ((glandulaeglandulae oesophageaeoesophageaepropriaepropriae))
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inin thethe upperupper oneone--thirdthird, , striatedstriated musclemuscle cancan be be foundfound, , onlyonly
inin thethe middlemiddle approximatelyapproximately oneone--thirdthirdsegmentssegments, , thethe striatedstriated andand smoothsmooth musclesmusclesareare intermingledintermingled
inin thethe lowerlower oneone--thirdthird, , therethere areare smoothsmoothmusclemuscle cellscells, , onlyonly
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tunicatunica adventitiaadventitia is is thethe outermostoutermost mainmain layerlayerofof thethe esophagusesophagus; ; thisthis layerlayer connectsconnects thethemajoritymajority ((cervicalcervical andand thoracicthoracic portionsportions) ) ofofthethe organorgan toto thethe surroundingsurrounding tissuetissue
thethe abdominalabdominal portionportion, , howeverhowever, is , is replacedreplacedbyby tunicatunica serosaserosa ((serousserous membranemembrane))
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beanbean--shaped hollow muscular organ of the shaped hollow muscular organ of the gastrogastro--intestinal tract involved in the second intestinal tract involved in the second phase of digestionphase of digestionitit has has fourfour anatomicalanatomical partsparts: : cardiacardia, fundus, , fundus, bodybody andand pyloruspylorusitit has has threethree histologicalhistological distinctdistinct partsparts: (1) : (1) cardiacardia, (2) , (2) thethe fundus fundus andand thethe bodybody havehave thethesamesame histologicalhistological propertiesproperties, (3) , (3) pyloruspylorus
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simplesimple columnarcolumnar epitheliumepithelium invaginatesinvaginatesintointo thethe laminalamina propriapropria, , therebythereby itit makesmakesgastricgastric pitspits ((foveolaefoveolae gastricaegastricae))thethe tubulartubular glandsglands ((cardiaccardiac --, , fundicfundic-- andandpyloricpyloric glandsglands) ) ofof stomachstomach emptyempty intointo thethebottombottom ofof thethe gastricgastric pitspitsthethe epithelialepithelial cellscells produceproduce thickthick, , neutralneutralmucinmucin, , whichwhich protectsprotects thethe cellscells themselvesthemselvesfromfrom highlyhighly acidicacidic gastricgastric juicejuice
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looseloose connectiveconnective tissuetissue, , whichwhich maymay containcontainmanymany lymphocyteslymphocytesallall thethe gastricgastric glandsglands areare locatedlocated inin thisthis laminalaminainin thethe threethree histologicalhistological portionsportions ofof thethestomachstomach thethe glandsglands display display somewhatsomewhatdifferentdifferent morphologymorphology; ; theirtheir productsproducts areare alsoalsodifferentdifferent
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a a laminalamina muscularismuscularis mucosaemucosaewellwell--developeddeveloped, , usuallyusually is is composedcomposed ofof twotwo sublayerssublayersofof smoothsmooth musclemuscle cellscells
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looseloose coonectingcoonecting tissuetissue, , containingcontainingbloodblood vesselsvessels
lymphaticslymphatics
lymphocyteslymphocytes
solitarysolitary fatfat cellscells
macrophagesmacrophages
mastmast cellscells
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containscontains smoothsmooth musclemuscle cellscellscomposedcomposed ofof sublayerssublayers::
outermostoutermost sublayersublayer:: discontinuousdiscontinuous; ; comprisecomprise mainlymainlylongitudinallylongitudinally orientedoriented smoothsmooth musclesmuscles cellscells, , whichwhich maymaybe be absentabsent fromfrom areasareas withinwithin thethe pyloricpyloric portionportionmiddlemiddle sublayersublayer: : circularlycircularly arrangedarranged smoothsmooth musclemuscle cellscells, , wellwell--developeddeveloped throughoutthroughout thethe stomachstomach; ; thethe middlemiddlesublayersublayer is is greatlygreatly enhancedenhanced inin thethe pyloricpyloric portionportion, , wherewhereitit isis calledcalled pyloricpyloric sphinctersphincter musclemuscleinnermostinnermost sublayersublayer: : obliqueoblique bundlesbundles ofof smoothsmooth musclemusclecellscells maymay occuroccur
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The The stomachstomach is is anan intraperitonealintraperitoneal organorgan. . ItsItsoutermostoutermost mainmain layerlayer isis a a serousserous membranemembraneofof looseloose coonectivecoonective tissuetissue andand mesotheliummesotheliumtowardstowards thethe peritonealperitoneal cavitycavity..
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locatedlocated inin thethe laminalamina propriapropria, , whichwhich arearedifferentdifferent inin thethe histologicalhistological portionsportions::
cardiaccardiac glandsglands
fundicfundic glandsglands
pyloricpyloric glandsglands
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simplesimple oror branchedbranched glandsglands, , locatedlocated inin thethe cardiaccardiacportionportion
thethe secretorysecretory cellscells resembleresemble thethe surfacesurface mucousmucous cellscellsofof thethe gastricgastric pitspits
produceproduce mucinmucin
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branchedbranched tubulartubular glandsglandsseveralseveral glandsglands openopen intointo oneone gastricgastric pitpithavehave segmentssegments
inin thethe upperupper segmentsegment (( neckneck ))neckneck mucousmucous cellscellsundifferentiatedundifferentiated stemstem cellscells
inin thethe middlemiddle andand lowerlower segmentssegments ((principalprincipalsegmentsegment))
H ClH Cl--producingproducing parietalparietal cellscellschiefchief cellscells, , whichwhich secretesecrete pepsinogenpepsinogenenteroendocrineenteroendocrine cellscells
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inin thethe pyloricpyloric regionregion, , thethe gastricgastric pitspits arearedeeperdeeper thanthan inin thethe otherother onesonesthethe pyloricpyloric glandsglands areare branchedbranched tubulartubularglandsglands withwith curvedcurved endsendsthethe secretorysecretory cellscells stainstain lightlylightlytheythey produceproduce mucin mucin andand antibacterialantibacteriallysozymelysozymeenteroentero--endocrineendocrine cellscells areare alsoalso presentpresent
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