Male Reproductive System

9/13/2014 Male reproductive system

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Wheater'sFunctionalHistology,SixthEdition

BarbaraYoung,GeraldineO'Dowd,andPhillipWoodford18,337350Copyright2014,2006,2000,1993,1987,1979byChurchillLivingstone,animprintofElsevierLtd.

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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


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


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)

Documents

Male Reproductive System