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Wheater'sFunctionalHistology,SixthEdition
BarbaraYoung,GeraldineO'Dowd,andPhillipWoodford18,337350Copyright2014,2006,2000,1993,1987,1979byChurchillLivingstone,animprintofElsevierLtd.
18
Malereproductivesystem
Introduction
Themalereproductivesystemisresponsiblefortheproductionofspermatozoaandtheirdeliveryintothefemalereproductivetractandmaybedividedintofourmajorfunctionalcomponents:
Thetestesormalegonads,pairedorganslyinginthescrotalsac,areresponsibleforproductionofthemalegametes,spermatozoa,andsecretionofmalesexhormones,principallytestosterone.
Asystemofductsconsistingofductuliefferentes,epididymis,ductus(vas)deferensandejaculatoryductcollects,storesandcarriesspermatozoafromeachtestis.Theejaculatoryductsconvergeontheurethra,fromwhichspermatozoaareexpelledintothefemalereproductivetractduringcopulation.
Twoexocrineglands,thepairedseminalvesiclesandthesingleprostategland,secreteanutritiveandlubricatingfluidmediumcalledseminalfluidinwhichspermatozoaareconveyedtothefemalereproductivetract.Semen,thefluidexpelledduringejaculation,consistsofseminalfluidandspermatozoa,plussomedesquamatedductliningcells.
Thepenisistheorganofcopulation.Apairofsmallaccessoryglands,thebulbourethralglandsofCowper,secreteafluidwhichlubricatestheurethraforthepassageofsemenduringejaculation.
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FIG.18.1
Malereproductivesystem
FIG.18.2
Testis
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Duringembryologicaldevelopment,eachtestiswiththefirstpartofitsductsystem,bloodvessels,lymphaticsandnervesdescendsfromtheposteriorwalloftheperitonealcavitytothescrotum.Duringmigration,thetestiscarrieswithitaninvestinglayerofperitoneumsothatinthescrotumthetestisisalmostcompletelysurroundedbyadoublelayerofmesothelium,enclosingapotentialspace.Thisdoubleliningiscalledthetunicavaginalisand,likethepleura,consistsofvisceralandparietallayers,separatedbyathinlayerofserousfluid.Thefluidissecretedbythemesothelialcellsandactsasalubricant,allowingthetestistomovefreelyinthescrotalsac.Theviscerallayerofthetunicavaginalisrestsonthecapsuleofthetestis,thetunicaalbuginea,whichgivesrisetonumerousincompletecollagenoussepta.Thesedividethetestisintoabout250testicularlobules.Withineachlobule,thereareonetofourhighlyconvolutedtubes,theseminiferoustubules,inwhichspermatozoaareproduced.Theseminiferoustubulesconvergeuponaplexusofchannels,theretetestis.Fromtheretetestis,15to20smallductscalledtheductuliefferentescarryspermatozoatotheextremelytortuousfirstpartoftheductusdeferens,whichisknownastheepididymis.
FIG.18.3
Testis,monkey
H&E(LP)
Thismicrographillustratesthemacroscopicfeaturesofatestiscutinthesagittalplane,itshowstherelationshiptotheepididymisE,whichliesonitsposterioraspect.Thetestisispackedwithcoiledseminiferoustubuleswhichcanjustbeseeninvariousplanesofsectionatthismagnification.GroupsofuptofourseminiferoustubulesaresegregatedintotesticularlobulesbyfineinterlobularseptaS.
Thedensefibrouscapsulewhichinveststhetestis,andwhichiscontinuouswithmanyoftheinterlobularsepta,iscalledthetunicaalbugineaTA.Itcontainsfibroblastsandabundantmyofibroblastsandsmoothmusclecells,particularlyintheposterioraspectclosetotheretetestis,whichsubjecttheseminiferoustissuetorhythmiccontractions.ScatteredLeydigcellsarealsofoundwithinthetunicaalbuginea.Thedeepestlayerofthetunicaalbugineaconsistsoflooseconnectivetissuecontainingbloodandlymphaticvessels,sometimescalledthetunicavasculosa.
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SpermatozoapassfromtheseminiferoustubulesintotheretetestisRT,whichisconnectedtotheepididymisviatheductuliefferentesattheupperposteriorpoleofthetestistheductuliarenotincludedintheplaneofthissection.Theepididymisisatightlycoiledtubewhichformsacompactmassextendingdownthewholelengthoftheposteriorsurfaceofthetestisandisthemajorsiteofstorageofnewlyformedspermatozoa.Atthelowerpoleofthetestis,theepididymaltubebecomescontinuouswiththerelativelystraightductus(vas)deferens,notseeninthissection.
Gametogenesis
Inallsomaticcells,celldivision(mitosis)resultsintheformationoftwodaughtercells,eachonegeneticallyidenticaltothemothercell.Somaticcellscontainafullcomplementofchromosomes(thediploidnumber)whichfunctionashomologouspairs(seeCh.2).Theprocessofsexualreproductioninvolvesthefusionofspecialisedmaleandfemalecellscalledgametestoformazygote,whichhasthediploidnumberofchromosomes.Eachgametecontainsonlyhalfthediploidnumberofchromosomes,onerepresentativeofeachpairthishalfcomplementofchromosomesisknownasthehaploidnumber.
Theproductionofhaploidcellsinvolvesauniqueformofcelldivisioncalledmeiosis,whichoccursonlyinthegermcellsofthegonadsduringtheformationofgametesmeioticcelldivisionisthusalsocalledgametogenesis.Meiosisinvolvestwocelldivisioncycles,ofwhichonlythefirstisprecededbyduplicationofchromosomes(seeCh.2).Thus,meioticcelldivisionofasinglediploidgermcellgivesrisetofourhaploidgametes.Inthemale,eachofthefourgametesundergoesmorphologicaldevelopmentintoamaturespermatozoon.Incontrast,inthefemale,unequaldistributionofthecytoplasmduringmeiosisresultsinonegametegainingalmostallthecytoplasmfromthemothercell,whiletheotherthreeacquirealmostnocytoplasmthelargegametematurestoformanovumandtheotherthree,calledpolarbodies,degenerate.
Theprimitivegermcellsofthemale,thespermatogonia,arepresentonlyinsmallnumbersinthemalegonadsbeforesexualmaturity.Afterpuberty,spermatogoniamultiplycontinuouslybymitosistoprovideasupplyofcellswhichthenundergomeiosistoformmalegametes.Incontrast,thegermcellsofthefemale,calledoogonia,multiplybymitosisonlyduringearlyfetaldevelopment,therebyproducingafixedcomplementofcellswiththepotentialtoundergogametogenesis.GametogenesisinthefemaleisdiscussedmorefullyinCh.19.Theproductionofmalegametesiscalledspermatogenesisandthesubsequentdevelopmentofthemalegameteintoamotilespermatozooniscalledspermiogenesis,thewholeprocesstakingapproximately70daysboththeseprocessesoccurwithinthetestes,althoughfinalmaturationofspermatozoaoccursintheepididymis.
FIG.18.4
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Seminiferoustubules
H&E(MP)
Thismicrographillustratesseminiferoustubulescutinvariousplanesofsection.Theseminiferoustubulesarehighlyconvolutedandarelinedby:
Germcellsinvariousstagesofspermatogenesisandspermiogenesis,whicharecollectivelyreferredtoasthespermatogenicseries
Nongermcells,calledSertolicells,whichsupportandnourishthedevelopingspermatozoaarealsofoundwithintheseminiferoustubules.
Intheinterstitialspacesbetweenthetubules,endocrinecellscalledLeydigcellsarefoundeithersinglyoringroupsinthesupportingtissue.
Inthismicrographofnormaltestisatmediumpower,notetheseminiferoustubulesSecutinvariousplanesofsection,givingroundandovoidprofiles.BetweentheseminiferoustubulestheinterstitiumIcontainsLeydigcells(whichcannotbediscernedatthismagnification)andsmallcapillariesC.Largerarteriesandveinsarefoundinthefibrousseptathatdividetheorganintolobules.
CcapillaryEepididymisIinterstitiumRTretetestisSinterlobularseptumSeseminiferoustubuleTAtunicaalbuginea
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FIG.18.5
Seminiferoustubule
(a)H&E(HP)(b)Diagram
Micrograph(a)illustratesanadultseminiferoustubulecutintransversesection.Theprocessesofspermatogenesisandspermiogenesisaresynchronised,withwavesofactivityoccurringsequentiallyalongthelengthofeachtubule.Thusinasinglecrosssectionofatubule,notalldevelopmentphaseswillberepresented(b).
Theundifferentiateddiploidgermcells,foundinthebasalcompartmentoftheseminiferoustubule,arecalledtypeAspermatogonia.ThesegothroughseveralcyclesofmitosistoproducefurthertypeAspermatogonia,whichmaintainthegermcellpool,andtypeBspermatogonia,whicharecommittedtoproductionofspermatozoa.SpermatogoniatypeASAarecharacterisedbyalargeroundorovalnucleuswithcondensedchromatinperipheralnucleoliandanuclearvacuolemaybeprominent.SpermatogoniatypeBSBhavedispersedchromatin,centralnucleoli,andnonuclearvacuole.Bothtypesofspermatogoniahavesparsepoorlystainedcytoplasm.
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TypeBspermatogoniaundergofurthermitoticdivisionstoproduceprimaryspermatocytes.Thesemigratetotheadluminalcompartmentoftheseminiferoustubulebeforecommencingthefirstmeioticdivision.PrimaryspermatocytesS1arereadilyrecognisedbytheircopiouscytoplasmandlargenucleicontainingcoarseclumpsorthinthreadsofchromatindividingcellsmaybeseen.Inhumans,thefirstmeioticdivisioncycletakesapproximately3weekstocomplete,afterwhichtimethedaughtercellsbecomeknownassecondaryspermatocytes.Thesmallersecondaryspermatocytesrapidlyundergothesecondmeioticdivisionandarethereforeseldomseen.
Thegametesthusproduced,calledspermatidsS3,thenproceedthroughthelongmaturationprocessknownasspermiogenesistobecomerecognisableasspermatozoa.Duringthisprocess,thenucleiofthespermatidsassumethesmallpointedformofspermatozoaS4(seeFig.18.7).Examinationofdifferentsectionsofthetubulesofanormaltestisshowsabouthalfthespermatogeniccellstobeinthelatespermatidstage.
Duringthedevelopmentalprocess,thecellsofthespermatogenicseriesaresupportedbySertolicellsSt,whosenucleiareusuallyfoundtowardsthebasementmembraneoftheseminiferoustubule.TheSertolicellnucleusistypicallytriangularorovoidinshapewithaprominentnucleolusanddispersedchromatin.
ThebasallayerofgerminalcellsissupportedbyabasementmembranewhichissurroundedbyalaminapropriacontainingseverallayersofspindleshapedmyofibroblastsMandfibroblasts.
FIG.18.6
Spermiogenesis
Spermiogenesisistheprocessbywhichspermatids,thegametesproducedbymeioticdivision,aretransformedintomotilematurespermatozoa.Thisinvolvesthefollowingmajorstages:
1.
TheGolgiapparatuselaboratesalargemembraneboundvesicle,theacrosomalvesicle,whichaccumulatescarbohydratesandhydrolyticenzymes.
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2.
Theacrosomalvesiclebecomesappliedtoonepoleoftheprogressivelyelongatingnucleustoformastructureknownastheacrosomalheadcap.
3.
Meanwhile,bothcentriolesmigratetotheendofthecelloppositetotheacrosomalheadcapthecentriolealignedparalleltothelongaxisofthenucleuselongatestoformaflagellumwhichhasabasicstructuresimilartothatofthecilium(seeFig.5.13).
4.
Astheflagellumelongates,ninecoarsefibrils,whichmaycontaincontractileproteins,becomearrangedlongitudinallyaroundthecoreoftheflagellum.Furtherriblikefibrilsthenbecomedisposedcircumferentiallyaroundthewholeflagellum.
5.
Thecytoplasmmigratestosurroundthefirstpartoftheflagellum.Theremainderoftheflagellumappearstoprojectfromthecellbutinfactremainssurroundedbyplasmamembrane.Thismigrationofcytoplasmthusconcentratesmitochondriaintheflagellarregion.
6.
Astheflagellumelongates,excesscytoplasmisphagocytosedbytheenvelopingSertolicellpriortoreleaseofthespermatidintothelumen,aprocesscalledspermiation.
Themitochondriabecomearrangedinahelicalmanneraroundthefibrilswhichsurroundthefirstpartoftheflagellum.
Thestructureoffullyformedspermatozoavariesindetailfromspeciestospeciesbutconformstothebasicstructureseeninthisdiagramofahumanspermatozoon.
Throughouttheentiredevelopmentalprocessfromspermatogoniatospermatozoa,hundredsofspermatidsremainconnectedtooneanotherbynarrowcytoplasmicbridgeswhichonlybreakdownuponreleaseofspermatozoaintothelumenoftheseminiferoustubule.Thisexplainsthesynchronousdevelopmentofspermatozoaatanyonepartofthetubule.
Sertolicellsareimportantintheregulationofspermatogenesisandspermiogenesis.Sertolicellsformtightjunctionswitheachotheraswellaswiththedevelopinggermcells.Itiswellestablishedthathighconcentrationsofandrogenhormones,secretedbyLeydigcellsofthetesticularinterstitium(seeFig.18.10),areessentialforproductionandmaturationofspermatogeniccells.Sertolicellssecreteanandrogenbindingproteinwhichtransportstestosteroneanddihydrotestosteronetothelumenoftheseminiferoustubule.Thesehormonesarealsonecessaryforfunctionoftheepitheliumoftheretetestisandepididymisproductionofthisbindingproteinisbelievedtobedependentonthepituitarygonadotrophinfolliclestimulatinghormone(FSH).
MmyofibroblastSAtypeAspermatogoniumSBtypeBspermatogoniumS1primaryspermatocyteS3spermatidS4spermatozoonStSertolicell
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FIG.18.7
Spermatozoa
(a)Head,LS,EM14000(b)Neck(middlepieceandprincipalpiece),LS,EM17000(c)Middlepiece,TS,EM48000
Theultrastructuralfeaturesofhumanspermatozoaareshowninthesemicrographs.Thespermatozoonisanextremelyelongatedcell(about65mlong)consistingofthreemaincomponents:thehead,neckandtail.Thetailissubdividedintothreesegments:themiddlepiece,principalpieceandendpiece(seeFig.18.6).
Theheadisthemostvariablestructurebetweendifferentmammalianspecies.Inhumanstheheadisabout7mlongandhasaflattenedpearshape.Asseeninmicrograph(a),thenucleus,whichoccupiesmostofthehead,iscomposedofverycondensedchromatininhumans,thiscontainsavariablenumberofareasofdispersedchromatincallednuclearvacuoles.SurroundingtheanteriortwothirdsofthenucleusistheacrosomalcapAC,aflattenedmembraneboundvesiclecontainingarangeofglycoproteinsandavarietyofhydrolyticenzymes,principallyhyaluronidasetheenzymesdisaggregatethecellsofthecoronaradiataanddissolvethezonapellucidaduringfertilisation(seeCh.19).NotetheplasmamembranePM,whichhasbecomepartiallyseparatedduringpreparation.
Theneckisaveryshortsegmentconnectingtheheadwiththetail.Itcontainsvestigesofthecentrioles,oneofwhichgivesrisetotheaxonemeAxoftheflagellum,whichisseeninmicrograph(c).Theaxonemehasthestandardnineplustwoarrangementofmicrotubuledoubletsseenincilia(seeFig.5.13).TheaxonemeoftheneckissurroundedbyseveralcondensedfibrousringsRnseeninmicrograph(b).Inhumanspermatozoa,asignificantamountofcytoplasmCyoftenremainsintheneckregion.
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Themiddlepiece,thefirstpartofthetail,isaboutthesamelengthastheheadandconsistsoftheflagellaraxonemesurroundedbyninecoarse(outerdense)fibresFarrangedlongitudinally.Externaltothiscore,elongatedmitochondriaMiarearrangedinatightlypackedhelixprovidingtheenergyrequiredforflagellarmovement.Afibrousthickeningbeneaththeplasmamembrane,calledtheannulusAn,preventsthemitochondriafromslippingintotheprincipalpiece.Theprincipalpiece,whichconstitutesmostofthetaillength,consistsofacentralcorecomprisingtheaxonemeandtheninecoarsefibrescontinuingfromthemiddlepiece.SurroundingthiscorearenumerousfibrousribsRbarrangedinacircularmannerandseeninmicrograph(b).Twoofthelongitudinalfibrilsofthecorearefusedwiththesurroundingribssoastoformdorsalandventralcolumnsextendingthroughoutthelengthoftheprincipalpiece(notillustrated).Thisarrangementdividestheprincipalpiecelongitudinallyintotwofunctionalcompartments,onecontainingthreecoarsefibrilsandtheothercontainingfour.Littleisknownofthemechanismofflagellarmotion,butthisasymmetrymayaccountforthemorepowerfulstrokeofthetailinonedirection,thesocalledpowerstrokethiscaneasilybeobservedinfreshlivepreparationsofspermatozoaviewedwiththelightmicroscope.Theendpiece,notshowninthesemicrographs,ismerelyashort,taperingportionofthetailcontainingtheaxonemeonly.
ACacrosomalcapAnannulusAVacrosomalvesicleAxaxonemeBMbasementmembraneCchromatinbodyCycytoplasmFouterdensefibresGGolgiapparatusMmyofibroblastMimitochondrionNunucleolusPMplasmamembraneRbfibrousribsRnfibrousringsSspermatogoniumStSertolicellS1primaryspermatocyteS3spermatidS4spermatozoon
FIG.18.8
Sertolicell
EM3400
TheintimaterelationshipofaSertolicellSttocellsofthespermatogenicseriesisdemonstratedinthiselectronmicrograph.
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TheSertolicellrestsonthebasementmembraneBMoftheseminiferoustubuleanditscytoplasmextendstothelumenofthetubule.Sertolicellshaveanextensivecytoplasmwhichramifiesthroughoutthewholegerminalepithelium,enclosingallthecellsofthespermatogenicseries.ThecytoplasmicoutlineoftheSertolicellisthushighlyirregularandconstantlychangingtopermittheprogressivemovementofdevelopingspermatozoatowardstheluminalsurface.TheovalnucleusoftheSertolicellischaracteristicallyorientatedatrightanglestothebasementmembraneandoftenexhibitsadeepindentation.AprominentnucleolusNuisaconstantfeatureanddensechromatinbodiesCareoftenassociatedwiththenucleolus.Thecytoplasmcontainsamoderatenumberofmitochondria,lipiddropletsandasmallamountofroughendoplasmicreticulum.Plentifulsmoothendoplasmicreticulumisalsopresent,aswellaslamellarproteinarraysknownasCharcotBottchercrystals(notshowninthiscell).
Sertolicellsareboundtooneanotherbyjunctionalcomplexescontainingextensivetightjunctions(seeCh.5).Thejunctionalcomplexislocatedtowardsthebasallayerofthespermatogenicepitheliumsoastodividethetubuleintobasalandadluminalcompartments.Thelattercontainsthespermatids,whicharethusisolatedbyabloodtestisbarrier.TheSertolicellsmediateallmetabolicexchangewiththesystemiccompartment.Thefunctionofthisbarrieristopreventexposureofgametes,whichareantigenicallydifferentfromsomaticcells,totheimmunesystem,thuspreventinganautoimmuneresponse.Sertolicellshavemultiplefunctionsincluding:
Secretionoffactorswhichregulatespermatogenesisandspermiogenesis
SecretionoffactorswhichregulatethefunctionofLeydigcellsandperitubularcells
Secretionofinhibinwhichregulateshormoneproduction
Secretionoftubularfluid
Phagocytosisofdiscardedspermatidcytoplasm
Avarietyofcellsofthespermatogenicseriesareseeninthismicrograph.SpermatogoniaSrestuponthebasementmembraneBM,beneathwhichisamyofibroblastM.Abovethegermcelllayer,primaryspermatocytesS1areseensecondaryspermatocytesareshortlivedandthereforerarelyseen.SpermatidsS3indifferentphasesofspermiogenesisareseeninupperlayersthesecellshavedevelopingacrosomalvesiclesAVelaboratedbyalargeGolgiapparatusG(seeFig.18.6).Attheluminalsurface,theSertolicellpartlyenvelopstheheadofanalmostfullyformedspermatozoonS4.
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FIG.18.9
Sertolicells(HP)
Immunohistochemicalmethodforinhibin
SertolicellscanbedifficulttoidentifyinstandardH&Estainedsections.However,thismicrographdemonstratestheextensivecytoplasmoftheSertolicellsastheyramifyaroundthecellsofthespermatogenicseries.Theimmunohistochemicalstainusesanantibodydirectedagainstinhibin,aproductofSertoliandLeydigcells,andsothecytoplasmofbothofthesecelltypesisstronglystainedbrownnotetheclusterofLeydigcellsLintheinterstitium.Thenucleiarenotstained.NotethematuringspermatozoaStowardsthelumenoftheseminiferoustubules.
FIG.18.10
Interstitial(Leydig)cellsofthetestis
H&E(HP)
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LeydigcellsL,theprincipalcelltypefoundintheinterstitialsupportingtissuebetweentheseminiferoustubules,synthesiseandsecretethemalesexhormonesandothernonsteroidsubstances.Theyoccursinglyorinclumpsandareembeddedintherichplexusofbloodandlymphcapillarieswhichsurroundstheseminiferoustubules.Thenucleusisroundwithdispersedchromatinandoneortwonucleoliattheperiphery.Theextensiveeosinophiliccytoplasmcontainsvariablenumbersoflipidvacuolesand,seenbyelectronmicroscopy,closelyresemblesthesteroidsecretingcellsoftheadrenalcortex(seeFig.17.16).Inhumans(andwildbushrats)butnootherspecies,LeydigcellsalsocontainelongatedcytoplasmiccrystalsofReinkewhicharelargeenoughtobeseenwithlightmicroscopywhensuitablystainedthesecrystalsarefoundonlyinadultsbuttheirfunctionisunknown.
TestosteroneisthemainhormonesecretedbyLeydigcells.Testosteroneisnotonlyresponsibleforthedevelopmentofmalesecondarysexualcharacteristicsatpubertybutisalsoessentialforthecontinuedfunctionoftheseminiferousepithelium.ThesecretoryactivityofLeydigcellsiscontrolledbythepituitarygonadotrophichormoneluteinisinghormone,sometimescalledinterstitialcellstimulatinghormone(ICSH)inthemale.
FIG.18.11
Retetestis
H&E(LP)
Theseminiferoustubulesconvergeuponthemediastinumtestis,whichconsistsofaplexiformarrangementofchannels,theretetestisRT,surroundedbyhighlyvascularcollagenoussupportingtissuecontainingmyoidcells.Theretetestisislinedbyasinglelayeroflowcuboidalepithelialcellswithsurfacemicrovilliandasinglecilium.
Myoidcellcontractionhelpstomixthespermatozoaandmovethemtowardstheepididymis.Theliningepitheliumreabsorbsproteinandpotassiumfromtheseminalfluid.Ciliaryactivityispresumedtoaidtheprogressofspermatozoa,whichdonotbecomemotileuntilaftermaturationiscompletedintheepididymis.
AappendixtestisBbasalcellDEductulusefferensLLeydigcellsRTretetestisSspermatozoaSMsmoothmuscleSTseminiferoustubule
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FIG18.12
Appendixtestis
H&E(LP)
Theappendixtestis(hydatidofMorgagni)isatinytagoftissueprotrudingfromtheanterosuperioraspectofthetestis.Itisimportantbecauseitmayundergotorsionleadingtolossofbloodsupplyandnecrosis(infarction),anextremelypainfulprocess.Theappendixtestisisaremnantofthemllerianductandispresentinapproximately80%ofmen.
TheappendixtestisAhasafibrovascularcoreandacuboidaltocolumnarsurfaceepitheliumwhichmaybeciliated(notvisibleatthismagnification).NotetheseminiferoustubulesSTintheadjacenttestis.
Otherappendagesinthisareaarethelesscommonappendixepididymis,thevasaberrans(organofHaller)andtheparadidymis(organofGiraldes).
FIG.18.13
Ductulusefferens
H&E(MP)
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Theretetestisdrainsintotheheadoftheepididymisviasome15to20convolutedducts,theductuliefferentesDE.Theductuliarelinedbyasinglelayerofepithelialcells,someofwhicharetallcolumnarandciliatedandotherswhichareshortandnonciliatedbothcelltypesoftencontainabrownpigmentofunknowncomposition.Ciliaryactionintheductulipropelsthestillnonmotilespermatozoatowardstheepididymis.Thenonciliatedcellsreabsorbsomeofthefluidproducedbythetestis.Basalcells,whichdonotreachthelumen,arealsopresentandprobablyactasstemcells.AthinbandofcircularlyarrangedsmoothmuscleSMsurroundseachductulusandaidspropulsionofthespermatozoatowardstheepididymis.
FIG.18.14
Epididymis
(a)H&E(LP)(b)H&E(HP)
Theepididymisisalong,extremelyconvolutedductextendingdowntheposterioraspectofthetestistothelowerpolewhereitbecomestheductus(vas)deferens.Theepididymisconsistsofaheadattheupperpoleofthetestis,abodylyingalongtheposteriormarginandatailatthelowerpoleofthetestis.Themajorfunctionoftheepididymisistheaccumulation,storageandmaturationofspermatozoaSintheepididymis,thespermatozoadevelopmotility.
Theepididymisisatubeofsmoothmusclelinedbyapseudostratifiedepithelium.Fromtheproximaltothedistalendoftheepididymis,themuscularwallincreasesfromasinglecircularlayerSM,asinthesemicrographs,tothreelayersorganisedinthesamemannerasintheductusdeferens(seeFig.18.15).Proximally,thesmoothmuscleexhibitsslow,rhythmiccontractilitywhichgentlymovesspermatozoatowardstheductusdeferens.Distally,thesmoothmuscleisrichlyinnervatedbythesympatheticnervoussystem,whichproducesintensecontractionsofthelowerpartoftheepididymisduringejaculation.
Theepithelialliningoftheepididymisexhibitsagradualtransitionfromatallpseudostratifiedcolumnarforminthehead,asseeninmicrograph(b),toashorterpseudostratifiedformatthetail.Theprincipalcellsoftheepididymalepitheliumbeartuftsofverylongmicrovilli,inappropriatelycalledstereocilia(seeFig.5.15),whicharethoughttobeinvolvedinabsorptionofanexcessoffluidaccompanyingthespermatozoafromthetestis.Theultrastructureofthecellsstronglysuggestsanadditionalsecretoryfunctionbutthenatureofepididymalsecretoryproducts,ifany,remainsunknown.BasalcellsBareprominentatthebaseoftheepithelium.
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FIG.18.15
Vasdeferens
H&E(LP)
Thevas(orductus)deferens,whichconductsspermatozoafromtheepididymistotheurethra,isathickwalledmusculartubeconsistingofinnerIandouterOlongitudinallayersandathickintermediatecircularlayerCI.Likethedistalpartoftheepididymis,thevasdeferensisinnervatedbythesympatheticnervoussystem,producingstrongperistalticcontractionstoexpelitscontentsintotheurethraduringejaculation.
Thevasdeferensislinedbyapseudostratifiedcolumnarepitheliumsimilartothatoftheepididymis(seeFig.18.14)theepitheliallininganditssupportinglaminapropriaarethrownintolongitudinalfolds,permittingexpansionoftheductduringejaculation.Thedilateddistalportionofeachvasdeferens,knownastheampulla,receivesashortductdrainingtheseminalvesicle,thusformingtheshortejaculatoryducttheejaculatoryductsfromeachsideconvergetojointheurethraasitpassesthroughtheprostategland.Inthislowpowermicrograph,theadiposetissueA,arteriesAAandveinsVthataccompanythevasareeasilyseentogetherthesestructurescomprisethespermaticcord.
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FIG.18.16
Seminalvesicle
(a)H&E(LP)(b)H&E(HP)
Eachseminalvesicleisacomplexglandulardiverticulumoftheassociatedductusdeferens.Betweenthem,theseminalvesiclessecrete5070%ofthetotalvolumeofseminalfluid,mostoftherestbeingsecretedbytheprostategland.Thelumenofeachseminalvesicleishighlyirregularandrecessed,givingahoneycombappearanceatlowmagnification.
Theepithelialliningisusuallyofapseudostratifiedtallcolumnartypeandconsistsofsecretorycellswithlipiddropletsinthecytoplasm,givingitafoamyappearance.Theseminalvesiclesproduceayellowishviscidalkalinefluidcontainingawiderangeofsubstances,includingfructose,fibrinogen,vitaminCandprostaglandins.TheepithelialcellsoftencontainbrownlipofuscingranulesLandcharacteristicallyhaverathervariablenuclearshapeandsize.Bothofthesefeaturesareseeninmicrograph(b).Althoughnotthoughttostorespermatozoa,seminalvesiclesareoftenseentocontainspermatozoawhichhaveprobablyenteredbyrefluxfromtheampulla.TheprominentmuscularwallMisarrangedintoinnercircularandouterlongitudinallayersandissuppliedbythesympatheticnervoussystemduringejaculation,musclecontractionforcessecretionsfromtheseminalvesiclesintotheurethraviatheampullae.
AadiposetissueAAarteryCverumontanumCapcapsuleCIintermediatecircularmusclelayerCZcentralzoneEDejaculatoryductIinnerlongitudinalmusclelayerLlipofuscingranulesMmuscularwallOouterlongitudinalmusclelayerPZperipheralzoneStfibrousstromaSpfibrousseptumTZtransitionalzoneUurethraVvein
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FIG.18.17
Prostategland
Theprostategland,whichinyoungadultsisaboutthesizeofawalnut,surroundsthebladderneckandthefirstpartoftheurethra,knownastheprostaticurethra.Theurethracoursesthroughtheprostatetobecomethemembranousurethraattheapexoftheprostate.Inthesubstanceofthegland,theurethramergeswiththeejaculatoryductsandatthispointanglesanteriorly.
Theprostateconsistsofbranchedtubuloacinarglands,embeddedinafibromuscularstroma.Thereisapartialcapsuleenclosingtheposteriorandlateralaspectsoftheprostatebuttheanteriorandapicalsurfacesareboundedbytheanteriorfibromuscularstroma,apartoftheglandconsisting,asthenameimplies,onlyofcollagenousstromaandmusclefibres.
Inthepast,theprostatewasdescribedasconsistingofanumberofilldefinedlobes.However,thisterminologyhasbeenreplacedbytheconceptofprostatezonesandtheglandisnowdescribedasconsistingoffourzonesofunequalsize:
Thetransitionzonesurroundstheproximalprostaticurethraandcomprisesabout5%oftheglandulartissue.
Thecentralzone(20%)surroundstheejaculatoryducts.
Theperipheralzonemakesupthebulkofthegland(approximately70%).
Theanteriorfibromuscularstromacontainsnoglandulartissueandliesanteriorly.
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FIG.18.18
Prostategland,dog
H&E(LP)
Thislowpowerviewoftheprostateofadogshowsthegeneralarchitecturalfeaturesofthegland.TheurethraUliescentrally,surroundedbyafibrousstromaSt.TheejaculatoryductsEDalsolieinthiscentralstromaastheycoursetowardstheirjunctionwiththeprostaticurethra.Thezonesoftheprostatearenotclearlydemarcatedfromeachotheranatomically.PartialfibrousseptaSpseparatetheglandintolobules.ThetransitionzoneTZsurroundsthefirstpartoftheprostaticurethra.ThecentralzoneCZliesposteriortothetransitionzoneandencirclestheejaculatoryductsED.TheperipheralzonePZmakesupthemainbulkofthegland.Theductsoftheperipheralzoneglandsemptyintotheposterolateralrecessesoftheurethraoneithersideoftheverumontanum(urethralcrest)C.
Thedifferentzonesoftheprostateareimportantbecausetheytendtobethesitesofdifferentdiseaseprocesses.Mostcasesofcarcinomaoftheprostateariseintheperipheralzone,whilethetransitionzoneharboursalmostallcasesofbenignnodularhyperplasia(seebelow).
AtthispowertheanteriorfibromuscularstromaappearscontinuouswiththecapsuleCapanditscontentofmusclefibrescannotbediscerned.
CommonprostaticdiseaseThemostcommondiseaseoftheprostateiscalledbenignprostatichyperplasiaandoccursinmenover50.Theprostaticglandsaroundtheurethra(transitionzone,seeFig.18.17)becomegreatlyincreasedinsizeandnumberandtheglandluminabecomedistendedbysecretionsandcorporaamylacea.Atthesametime,thestromalsmoothmusclefibresbecomegreatlyenlarged.Thisincreaseinbulkenlargestheprostateglandasawhole,andcompressestheurethra,leadingtointerferencewithbladderemptying.
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FIG.18.19
Prostategland
(a)H&E(LP)(b)H&E(HP)
Theprostateglandiscomposedofglandsandstroma.ThesupportingstromaSSisamixtureofcollagenousfibroustissueandsmoothmusclefibres,whicharebestseenathighermagnificationinmicrograph(b).TheglandsGshowaconvolutedpatternwiththeepitheliumthrownupintofolds,sometimesintoalmostapapillarypattern.
Thesecretoryproductoftheprostate,whichmakesupabout3050%theseminalfluidvolume,isathinliquidrichincitricacidandproteolyticenzymes,includingfibrinolysins,whichliquefiesthecoagulatedsemenafterithasbeendepositedinthevagina.Inspissatedsecretionsmayaccumulateinsomeglandstoformsphericalconcretions(corporaamylacea)whichincreaseinnumberwithageandmaybecomecalcified(notseeninthisexample).
Micrograph(b),takenathighermagnification,showsthedetailoftheepitheliumoftheprostateglands.Themainepithelialcelltypeisthetallcolumnarsecretorycellwithprominentroundbasalnucleiandpalestainingcytoplasm.Thereisalsoascantypopulationofsmall,flat,basalcellsatthebaseoftheglandincontactwiththebasementmembrane.Thebasalcellsareeasilyseeninthismicrograph.Thesecellsactasstemcellsandmaybecomequiteprominentinprostatichyperplasia.
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FIG.18.20
Penis
H&E(LP)
Thistransversesectionofthehumanpenisshowsthearrangementoftheerectiletissues,whichexistintheformofthreecolumns.ThetwodorsalcolumnsarecalledthecorporacavernosaCCandthesingleventralcolumnisthecorpusspongiosumCSthroughwhichrunsthepenileurethraU.Atitsdistalend,thecorpusspongiosumexpandstoformtheglanspenis.TheerectilecorporaareenclosedwithinandseparatedbyafibrocollagenouscapsuleF.TheerectilecentreofthepenisisenclosedinasheathofskinStowhichitisconnectedbyaloosesubcutiscontainingprominentbloodvessels.
FIG.18.21
Corpusspongiosum
H&E(LP)
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Thecorpusspongiosumiscomposedoferectiletissue,largeirregularinterconnectedvascularchannelswithfibrocollagenousstromabetweenthestromacontainssomesmoothmusclefibres.RunningthroughthecentreofthecorpusspongiosumisthepenileurethraU.Smallparaurethralmucusglandsopenintotheurethra.
FIG.18.22
Penileerectiletissue
H&E(LP)
ThevascularsinusesSiofthecavernousbodiesofthepenisaresuppliedbynumerousanastomosingthickwalledarteriesandarteriolescalledhelicinearteriesHA,sincetheyfollowaspiralcourseintheflaccidstate.Blooddrainsfromthesinusesviaveinswhichlieimmediatelybeneaththedensefibroelastictissueinvestingthecavernousbodies.Duringerection,dilatationofthehelicinearteries,mediatedbytheparasympatheticnervoussystem,resultsinengorgementofthevascularsinuses,whichenlarge,compressingandrestrictingvenousoutflow.Theprocessisenhancedbyrelaxationofsmoothmusclecellsinthetrabeculaeofthecavernousbodies.
FIG.18.23
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Penileurethra
H&E(HP)
Apartfromtheprostaticurethra,whichislinedbytransitionalepithelium,themaleurethraislinedbystratifiedorpseudostratifiedcolumnarepithelium,althoughsmallareasofstratifiedsquamousepitheliummayalsobefoundinhumanadultmales.Theexternalopening(urethralmeatus)islinedbystratifiedsquamousepitheliumwhichbecomescontinuouswiththeepitheliumoftheglans.
TheurethraislubricatedbymucoussecretionsfromtheparaurethralglandsPandthebulbourethralglandsofCowper(seeFig.18.1),whichhaveasimilarbutmorediscreteorganisation.
BbasalcellCCcorpuscavernosumCScorpusspongiosumFfibrocollagenouscapsuleGglandHAhelicinearteryPparaurethralglandSskinSivascularsinusSSsupportingstromaUurethra
FIG.18.24
Semen
H&E(HP)
Semen,theproductofejaculation,consistsofspermatozoaandseminalfluid,whichisderivedprincipallyfromtheseminalvesiclesandprostategland.Thevolumeofeachhumanejaculateisabout3.5mL,containingfrom50to150106spermatozoapermL.Innormalfertilehumanmales,upto25%oftheejaculatedspermatozoaareabnormalordegenerateforms.Bythetimeofejaculation,spermatozoahavematuredandacquiredthepropertyofmotilitynevertheless,theyremainincapableoffertilisinganovumuntilafterundergoingaprocesscalledcapacitationwithinthefemalegenitaltract.
Review
TABLE18.1
Reviewofmalegenitaltract
Organ Maincomponents Celltypes Functions
Testis
Seminiferoustubules SpermatogenicseriescellsSertolicells
Productionofmalegametes,spermatozoaSupportcellsforspermatogenesis
Interstitium LeydigcellsSynthesisofandrogenichormones,principallytestosterone
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RetetestisCuboidalepitheliumwithciliaandsmoothmusclecoat
Conveyspermatozoatoductulesefferentesandthencetoepididymis
EpididymisColumnarepitheliumwithstereociliaandsmoothmusclecoat
Storeandmaturespermatozoa
Vasdeferens
Columnarepitheliumandsmoothmusclecoat,threelayers
Carryspermtourethraduringejaculation
Prostate
Central,transitionandperipheralzonesandanteriorfibromuscularstroma
Epitheliumwithtwocelllayers,luminaltallcolumnarlayerandbasalcelllayer
Producessecretionsthatmixwithseminalfluid
Seminalvesicle
Cuboidaltocolumnarepitheliumwithmuscularwall
Produceseminalfluid
Penis Corpusspongiosumandcorporacavernosa
Spongyfibroustissuecontaininganastomosingvascularsinuses
Erectiletissue
UrethraLinedbyurotheliumproximallyPseudostratifiedcolumnarepitheliumdistally
Ductforejaculation(andmicturition)
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