-- composedcomposed ofof thethe alimentaryalimentary canalcanal andand thetheassociatedassociated glandsglands

-- thethe alimentaryalimentary canalcanal is a is a longlong, , tortuoustortuoustubetube, , whichwhich beginsbegins withwith thethe lipslips andandterminatesterminates withwith thethe anusanus

Common properties of the wall of the Common properties of the wall of the digestive tractdigestive tract

The The wallwall is is composedcomposed ofof thethe followingfollowing layerslayersasas followsfollows fromfrom thethe lumen:lumen:

1.1. TunicaTunica mucosamucosa ((mucousmucous membranemembrane))

2.2. TunicaTunica submucosasubmucosa

3.3. TunicaTunica muscularismuscularis

4.4. TunicaTunica serosaserosa ((serousserous membranemembrane) ) ororadventitiaadventitia

thethe most most inportantinportant layerlayer withwith variousvarious tissuetissuecomponentscomponents

has has diversediverse functionsfunctions::

-- protectionprotection

-- secretionsecretion

-- absorptionabsorption

-- sublayerssublayers ofof thethe submucosasubmucosa::

1./a. 1./a. laminalamina epithelialisepithelialis -- epitheliumepithelium

1./b. 1./b. laminalamina propriapropria connectiveconnective tissuetissueproperproper

1./c. 1./c. laminalamina muscularismuscularis mucosaemucosae smoothsmoothmusclemuscle

adluminaladluminal, covering epithelium, covering epitheliumfunctions:functions:

physicochemical barrier between the lumen physicochemical barrier between the lumen and the connective tissueand the connective tissueselective aselective absorptionbsorption ofof thethe digesteddigestedsubstancessubstancessesecretioncretion ofof digestivedigestive enzymesenzymes andand lubricatinglubricatingmucinsmucins

thethe typestypes ofof thethe epitheliumepithelium reflectsreflects thethespecialspecial demandsdemands ofof thethe appropriateappropriatesegmentssegments ofof thethe alimentaryalimentary canalcanalexamplesexamples::

oraloral cavitycavity, , esophagusesophagus stratifiedstratified, , nonkeratinizednonkeratinized squamoussquamous epitheliumepitheliumstomachstomach simplesimple columnarcolumnar epitheliumepitheliumsmallsmall intestineintestine simplesimple columnarcolumnar epitheliumepitheliumwithwith cuticlecuticle

looseloose connectiveconnective tissuetissue, , whichwhich containscontains bloodblood --andand lymphaticlymphatic vesselsvessels, , nervenerve fibersfibers andand differentdifferentkindskinds ofof connectiveconnective tissuetissue cellscells

inin thethe laminalamina propriapropria ofof most most segmentssegments ofof thetheG.I.T., G.I .T., therethere areare tubulartubular glandsglands, , suchsuch asas thethegastricgastric -- andand intestinalintestinal glandsglands

elementselements ofof thethe immuneimmune systemsystem is is presentpresentthroughoutthroughout thethe G.I.T. G.I .T. toto defenddefend thethe bodybodyagainstagainst possiblepossible bacterialbacterial attacksattacks

thinthin layerlayer ofof smoothsmooth musclemuscle, , whichwhich is is oftenoften composedcomposed ofof anan innerinner circularcircular andandouterouter longitudinallongitudinal sublayerssublayers

contributescontributes toto thethe motilitymotility ofof thethe mucousmucousmembranemembrane; ; thisthis movementmovement is is independentindependentofof thethe peristalticperistaltic movementmovement ofof thethe tracttract

connectiveconnective tissuetissue layerlayer withwith variousvarious thicknessthickness; ; here here bloodblood vesselsvessels runruncontainscontains plexusplexus ofof lymphaticslymphaticscontainscontains vegetativevegetative ganglionganglion cellscells andand peripheralperipheralnervesnerves, , whichwhich togethertogether makemake thethe submucoussubmucousplexusplexus ofof MeisnerMeisnermaymay containcontain glandsglands inin thethe submucosasubmucosa ofof certaincertainsegmentssegments ((esophagusesophagus andand duodenumduodenum))

relativelyrelatively thickthick layerlayer withwith twotwo sublayerssublayers ofofsmoothsmooth musclemuscle inin thethe vastvast majoritymajority ofof casescasesinnerinner circularcircular sublayersublayer ((strstr. . circularecirculare))outerouter longitudinallongitudinal sublayersublayer ((strstr. . longitudinalelongitudinale))thethe sublayerssublayers areare separatedseparated byby thinthin connectiveconnectivetissuetissue containingcontaining thethe myentericmyenteric plexusplexus ofofAuerbachAuerbach asas wellwell asas bloodblood andand lymphaticlymphatic vesselsvessels

therethere areare striatedstriated musclesmuscles inin thethe proximalproximalsegmentssegments ofof thethe esophagusesophagus, , andand alsoalso inin thetheanalanal canalcanal

therethere is a is a thirdthird muscularmuscular sublayersublayer inin thethe wallwall ofofthethe stomachstomach: : innerinner obliqueoblique fibersfibers

inin thethe largelarge intestineintestine, , thethe externalexternal sublayersublayerformsforms longitudinallongitudinal bandsbands ofof smoothsmooth musclemuscletaeniaetaeniae colicoli

tunicatunica serosaserosa ((serousserous membranemembrane)) is is thetheoutermostoutermost layerlayer ofof thosethose segmentssegments ofof thethealimentaryalimentary canalcanal thatthat areare envelopedenveloped bybyperitoneumperitoneum

has has simplesimple squamoussquamous epitheliumepithelium ((laminalaminaepithelialisepithelialis; ; mesotheliummesothelium) ) andand a a thinthin connectiveconnectivetissuetissue sublayersublayer (( laminalamina propriapropria serosaeserosae))

thethe serousserous membranemembrane is is attachedattached toto thethemuscularismuscularis throughthrough a a subseroussubserous connectiveconnectivetissuetissue

TunicaTunica advenitiaadvenitia

certaincertain segmentssegments ofof thethe G.I .T. G.I .T. areare notnotenvelopedenveloped byby peritoneumperitoneum

inin thesethese segmentssegments, , thethe outermostoutermost layerlayer is is looseloose connectiveconnective tissuetissue ((adventitiaadventitia)), , whichwhichconnectsconnects thethe tracttract toto thethe itsits surroundingssurroundings

salivarysalivary glandsglands inin thethe laminalamina propriapropria mucosaemucosae

submucoussubmucous glandsglands inin thethe telatela submucosasubmucosa

extramuralextramural glandsglands (( largelarge digestivedigestive glandsglands) ) arearelocatedlocated outsideoutside thethe wallwall ofof thethe tracttract; ; theytheydischargedischarge theirtheir productsproducts intointo G.I .T. lumen G.I .T. lumen throughthrough excretoryexcretory ductsducts

characteristiccharacteristic anatomicalanatomical itemsitems::lipslips

teethteeth

toungetounge

salivarysalivary glandsglands

borderborder thethe mouthmouth openingopening ((oraloral fissurefissure))

therethere scaffoldingsscaffoldings areare striatedstriated musclemusclefibersfibers ofof thethe orbicularisorbicularis orisoris m.m.

havehave cutaneouscutaneous andand mucousmucous surfacessurfaces((parspars cutaneacutanea andand parspars mucosamucosa))

ParsPars cutaneacutanea -- outerouter surfacesurface, , whichwhich is is composedcomposed ofof skinskin ((epidermisepidermis, , dermisdermis andand hypodermishypodermis, , whichwhich isis alsoalso calledcalled subcutaneoussubcutaneous tissuetissue). ). InIn thisthis surfacesurface, , therethere variousvarious derivativesderivatives ofof thethe skinskin: : hairhair folliclesfollicles, , sebaceoussebaceous andand sweatsweat glandsglands..

ParsPars mucosamucosa innerinner surfacesurface, , whichwhich lineslines thethe oraloral cavitycavity. . ThisThissurfacesurface is is coveredcovered byby a a mucousmucous membranemembrane, , containingcontaining stratifiedstratified, , nonkeratinizednonkeratinized, , squamoussquamous epitheliumepithelium andand connectiveconnective tissuetissue. . InIn thethelaterlater layerlayer therethere areare smallsmall salivarysalivary glandsglands: : labiallabial glandsglands..

RuborRubor labiilabii -- vermilionvermilion zonezone betweenbetween thethe ordinaryordinary skinskin andand thethemucousmucous membranemembrane. The . The vermilionvermilion zonezone is is coveredcovered byby stratifiedstratified, , keratinizedkeratinized, , squamoussquamous epitheliumepithelium. . ThisThis zonezone isis devoiddevoid ofof skinskinappendagesappendages. . HoweverHowever, , thethe zonezone has has capillarycapillary--richrich connectiveconnective tissuetissuepapillaepapillae, , thethe redred colorcolor ofof whichwhich maymay be be wellwell visiblevisible throughthrough thetherelativelyrelatively thinthin skinskin..

The The tonguetongue is a is a muscularmuscular organorgan, , coveredcovered bybymucousmucous membranemembrane. . I tsI ts mainmain massmass is is striatedstriatedmusclemuscle, , fibersfibers ofof whichwhich runrun inin allall directionsdirections ofofspacespace. . ThisThis sort sort ofof organizationorganization is is highlyhighly typicaltypicalofof thethe tonguetongue..

The The mucousmucous membranemembrane onon thethe superiorsuperior andandinferiorinferior surfacessurfaces areare veryvery muchmuch differentdifferent..

OnOn thethe superiorsuperior surfacesurface ((dorsumdorsum ofof tonguetongue)), , therethere areare linguallingual papillaepapillae..

BehindBehind thethe sulcussulcus terminalisterminalis,, therethere arearelymphaticlymphatic folliclesfollicles ofof thethe linguallingual tonsiltonsil..

The The mucosemucose membranemembrane ofof thethe inferiorinferiorsurfacesurface is is smoothsmooth, , lackslacks connectiveconnectivetissuetissue papillaepapillae..

serosusserosus glandsglands ofof EbnerEbner, , whichwhich openopen atat thethebasebase ofof vallatevallate -- andand foliatefoliate papillaepapillae

mucinousmucinous glandsglands inin thethe rootroot ofof tonguetongueposteriorposterior linguallingual glandsglands

mixedmixed glandsglands inin thethe apexapex ofof tonguetongueanterioranterior linguallingual glandsglands ((glandgland ofof BlandinBlandin andandNuhnNuhn))

filiformfiliform papillaepapillae

fungiformfungiform papillaepapillae

foliatafoliata papillaepapillae

vallataevallatae papillaepapillae

theythey areare locatedlocated inin front front ofof thethe sulcussulcus terminalisterminalis

largelarge, , roundishroundish linguallingual papillaepapillae withwith a a diameterdiameterofof 22--3 mm; 3 mm; thusthus, , theythey cancan be be readilyreadily seenseen withwithnakednaked eyeseyes

oneone manman has 8has 8--12 12 vallatevallate papillaepapillae

havehave tastetaste budsbuds inin theirtheir wallswalls

eacheach papilla is papilla is encircledencircled byby a a moatmoat--likelike trenchtrench

thethe EbnerEbner ss serousserous glandsglands emptyempty intointo thethe moatsmoatsofof thethe papillaepapillae

areare lightlylightly stainedstained ovaloval bodiesbodies, , locatedlocated inin thethestratifiedstratified, , nonkeratinizednonkeratinized, , squamoussquamous epitheliumepitheliumofof thethe mucousmucous membranemembranecellcell typestypes::

supportingsupporting cellscellssecondarysecondary neuroepithelialneuroepithelial cellscellsundifferentiatedundifferentiated stemstem cellscells

PartsPartscrowncrown ofof toothtoothneckneck ofof toothtoothrootroot ofof toothtooth

insideinside thethe crowncrown andand neckneck, , therethere is a is a toothtoothpulppulp, , insideinside thethe rootroot, , therethere is a is a rootroot canalcanal, , whichwhich opensopens inin thethe apicalapical foramenforamen

Dentin (Dentin (substantiasubstantia eburneaeburnea))

EnamelEnamel ((substantiasubstantia adamantinaadamantina, , enamelumenamelum))

CementumCementum ((substantiasubstantia osseaossea, , cementumcementum))

inorganicinorganic substancessubstances: 80%: 80%hydroxyhydroxy--apatiteapatite crystalscrystals

organicorganic substancessubstances: 20%: 20%itsits 9/10: 9/10: typetype I I collagencollagenitsits 1/10: 1/10: proteoglycansproteoglycans

EnamelEnamel

inorganicinorganic substancessubstances: 98%: 98%

hydroxyhydroxy--apatiteapatite crystalscrystals

organicorganic substancessubstances: 2%: 2%

insolubleinsoluble proteinsproteins

ThereThere areare NO NO cellscells withinwithin thethe enamelenamel!!

CementumCementum

coverscovers thethe rootsroots ofof teethteethcementoblastscementoblasts produceproduce; ; thethe resting resting cellscells arearecementocytescementocytesinorganicinorganic substancessubstances: 50%: 50%organicorganic contentcontent is is mainlymainly mademade upup ofof collagencollagen fibersfibersthethe cementumcementum is is tetheredtethered toto thethe periodontiumperiodontium bybySharpeySharpey ss fibersfibers

PARODONTIUMPARODONTIUM

CementumCementumPeriodontiumPeriodontium connectingconnecting tissuetissuemembranemembrane, , whichwhich is is ririchch inin fibersfibers; ; containscontainsbloodblood vesselsvessels andand nervesnerves. . ItsIts cellscells arearefibroblastsfibroblasts, , whichwhich cancan be be convertedconverted eithereithercementoblastscementoblasts oror osteoblastsosteoblasts ofof alveolaralveolarbonebone..AlveolarAlveolar bonebone

looseloose connectingconnecting tissuetissue, , whichwhich is is richrich inincapillariescapillaries andand nervesnerves

cellscells::fibroblastsfibroblasts, , mastmast cellscells, , macrophagesmacrophages, , lymphocyteslymphocytes

odontoblastsodontoblasts, , whichwhich produceproduce thethe dentindentin

SmallSmall salivarysalivary glandsglands labiallabial, , buccalbuccal, , palatinepalatine, , lingualeslinguales, , etcetc. . glandsglands

LargeLarge salivarysalivary glandsglands parotidparotid, , submandibularsubmandibular, , sublingualsublingualglandsglands

AllAll ofof themthem areare exocrineexocrine glandsglands..

secretorysecretory portionportion cancan be be serousserous, , mucousmucousoror mixedmixed // GianuzziGianuzzi ss demilunedemilune//

excretoryexcretory portionportionintralobularintralobular ductsducts intercalatedintercalated tubulestubules, , striatedstriatedductsducts

interlobularinterlobular ductsducts excretoryexcretory ductsducts

purelypurely serousserous glandglandtherethere areare manymany fatfat cellscells amongamong thethe aciniaciniwellwell--developeddeveloped intercalatedintercalated tubulestubules andand salivarysalivaryductsductsinin thethe interlobularinterlobular septasepta, , runrun thethe largerlarger excretoryexcretoryductsducts, , bloodblood vesselsvessels andand peripheralperipheral nervesnervestherethere maymay be be manymany crosscross--sectionssections ofof thethebranchesbranches ofof thethe facialfacial nervenerve, , whichwhich passpass thetheparotidparotid

mixedmixed glandgland, , butbut thethe mucousmucous secretorysecretorycellscells predominatepredominate overover thethe serousserous onesones..

thethe serousserous cellscells areare locatedlocated asas smallsmallclustersclusters aroundaround thethe mucousmucous aciniacini: : thesetheseareare GianuzziGianuzzi demilumesdemilumes

bothboth thethe intercalatedintercalated tubulestubules andand thethestriatedstriated ductsducts areare usuallyusually absentabsent

mixedmixed glandgland, , inin whichwhich thethe serousserous secretorysecretorycellscells predominatepredominate

thethe scatteredscattered mucousmucous aciniacini areare partlypartlycoveredcovered byby serousserous capcap // GianuzziGianuzzi ssdemilunedemilune//

therethere areare somewhatsomewhat smallersmaller numbernumberintercalatedintercalated tubulestubules andand striatedstriated ductsductsthanthan inin thethe parotidparotid