内蒙古大学生殖生物学课件01Reproductive System

ReproductiveBiologyChapterOne:ReproductiveSystemreproductivesystemsAnimals’reproductivesystemscanbedividedintotheinternalreproductiveorgansandtheexternalgenitalia.Thegonadsaretheactualorgansthatproducethegametes.Inthemale,testes(singular=testis)producesperm,andinthefemale,ovariesmakeeggs.Diversityofreproduction

AsexualreproductionParthenogenesisHermaphroditesSequentialhermaphrodites-protogyny(FM)orprotoandry(MF)Sexualreproduction

Male/femalereproductivestrategyAsymmetricalgametesize(anisogamy异配生殖)meansthesexwithsmallergametesshouldusuallycompeteforaccesstothesexwithlargergametes.Thisresultsingreatervariationamongmalesthanamongfemalesforreproductivesuccess.Inmostanimals,individualsareeitherdefinitemalesordefinitefemales.However,insomespecies,individualorganismsarebothmaleandfemale.Hermaphroditismiswhenoneorganismhasbothsexes.Earthwormsandgardensnailsalwayshavebothmaleandfemaleorgans,andwhen,forexample,twoearthwormsmate,theyfertilizeeachother.Aspecialvariationonthethemeissequentialhermaphroditism(顺序型雌雄同体

),inwhichanorganismchangessexduringitslife.Ifanorganismisfemalefirstandlaterchangestomale,thatorganismisprotogynous(雌性先熟，如巨石斑鱼),andiftheorganismismalefirstandchangestofemale,itissaidtobeprotandrous（雄性先熟）.Indifferentspecies,sequentialhermaphroditismcanbeinfluencedbytheorganism’sageorsizeorbyvariousenvironmental/climaticfactors.

Anthinesareexamplesofsynchronousprotogynoushermaphrodites.Theyarebornwithanundifferentiatedgender,laterturnintofemales,andthencanbecomemaleswhenprovidedwiththerightcues.Picturedhere,a

Pseudanthias

squamipinnisisinanintermediatestagebetweenfemaleandmale.Keeponlyonemalepertank,andfeedsmall,frequentportionsoffood(2-3timesdaily).PhotobyAnthonyCalfo.ParthenogenesisWhilemosthigheranimalsreproducesexually,therearesomespeciesinwhichthefemalescan,undercertainconditions,produceoffspringwithoutmating.Parthenogenesis

istheabilityofanunfertilizedeggtodevelopandhatch.Thisseemstobeespeciallyprevalentamonginsects.Someofthegiantwalkingsticks（竹节虫）attheZooarefemaleswho,withoutmating,layeggsthathatchintomorefemalesgenerationaftergeneration.Otherinsects,likesomeaphids（蚜虫）,havecomplicatedlifecyclesthatinvolvesexually-reproducinggenerationsalternatingwithparthenogenicallyproducedgenerations.Inhoneybees,fertilizedeggsturnintofemales(workersandqueens),whileunfertilizedeggs,whichareonlyproducedinthespring,turnintomales.external/internalfertilizationInsexualreproduction,theremustbesomewayofgettingthespermtotheegg.Sincespermandeggsaredesignedtobeinawateryenvironment,aquaticanimalscanmakeuseofthewaterinwhichtheylive,butterrestrial（陆生）animalsmust,insomeway,providethewetenvironmentneededforthespermtoswimtotheegg.Thereare,thus,twomajormechanismsoffertilization.Inexternalfertilization,usedbymanyaquaticinvertebrates,eggsandspermaresimultaneouslyshedintothewater,andthespermswimthroughthewatertofertilzetheegg.Ininternalfertilization,theeggsarefertilizedwithinthereproductivetractofthefemale,andthenarecoveredwitheggshellsand/orremainwithinthebodyofthefemaleduringtheirdevelopment.MannersofReproductionInspecieswithexternalfertilization,atanappropriatedevelopmentalstage,theeggshatch,andthenewyoungsimplyswimaway.However,femalesofspecieswithinternalfertilizationmust,atsomepoint,expelthegrowingyoung.Therearethreegeneralwaysofdoingthis:Oviparous(卵生)organisms,likechickensandturtles,layeggsthatcontinuetodevelopafterbeinglaid,andhatchlater.Viviparous（胎生）

organisms,likehumansandkangaroos,arelive-bearing.Thedevelopingyoungspendproportionatelymoretimewithinthefemale’sreproductivetract,portionsofwhicharespecially-modifiedforthispurpose.Youngarelaterreleasedtosurviveontheirown.Ovoviviparous

（卵胎生）organisms,likeguppies（孔雀鱼）,gartersnakes（

肉食性束带蛇）,andMadagascarhissingroaches（马达加斯加发声蟑螂）,haveeggs(withshells)thathatchastheyarelaid,makingitlooklike“livebirth.”MaleReproductiveSystemThemalereproductivesystemisillustratedtotheright.Spermareproducedinthetesteslocatedinthescrotum（阴囊）.Normalbodytemperatureistoohotthusislethal（致命的）tospermsothetestesareoutsideoftheabdominalcavitywherethetemperatureisabout2°C(3.6°F)lower.Becarefulofyourbluejeans!!!Temperatureissoimportantforthesperm!Notealsothatawoman’sbodytemperatureislowestaroundthetimeofovulationtohelpinsurespermlivelongertoreachtheegg.Ifamantakestoomanylong,veryhotbaths,thiscanreducehisspermcount.Undescendedtestes(testesaresupposedtodescendbeforebirth)willcausesterilitybecausetheirenvironmentistoowarmforspermviabilityunlesstheproblemcanbesurgicallycorrected.EpididymisFromthere,spermaretransferredtotheepididymis,coiledtubulesalsofoundwithinthescrotum,thatstorespermandarethesiteoftheirfinalmaturation.Ejaculationandvasdeferens

Inejaculation,spermareforcedupintothevasdeferens(plural=vasa

deferentia).Fromtheepididymis,thevasdeferensgoesup,aroundthefrontof,overthetopof,andbehindthebladder.Avasectomyisafairlysimple,outpatient(门诊患者)operationthatinvolvesmakingasmallslitineachscrotum,cuttingthevasa

deferentia

nearwheretheybegin,andtyingoffthecutendstopreventspermfromleavingthescrotum.Becausethisisarelativelynon-invasiveprocedure(ascomparedtodoingthesametoawoman’soviducts),thisisapopularmethodofpermanentbirthcontrolonceacouplehashadallthechildrentheydesire.Couplesshouldcarefullyweightheiroptions,becausethis(andthecorrespondingfemaleprocedure)isnotdesignedtobeareversibleoperation.ejaculatoryducts/seminalvesicles/semen/urethra

Theendsofthevasa

deferentia,behindandslightlyunderthebladder,arecalledtheejaculatoryducts.Theseminalvesiclesarealsolocatedbehindthebladder.Theirsecretionsareabout60%ofthetotalvolumeofthesemen(=spermandassociatedfluid)andcontainmucus,aminoacids,fructoseasthemainenergysourceforthesperm,andprostaglandinstostimulatefemaleuterinecontractionstomovethesemenupintotheuterus.Theseminalvesiclesemptyintotheejaculatoryducts.Theejaculatoryductsthenemptyintotheurethra(which,inmales,alsoemptiestheurinarybladder).prostateglandTheinitialsegmentoftheurethraissurroundedbytheprostategland(notespelling!).Theprostateisthelargestoftheaccessoryglandsandputsitssecretionsdirectlyintotheurethra.Thesesecretionsarealkalinetobufferanyresidualurine,whichtendstobeacidic,andtheacidityofthewoman’svagina.Theprostateneedsalotofzinctofunctionproperly,andinsufficientdietaryzinc(aswellasothercauses)canleadtoenlargementwhichpotentiallycanconstricttheurethratothepointofinterferringwithurination.Mildcasesofprostatehypertrophy(肥大、增生)canoftenbetreatedbyaddingsupplementalzinctotheman’sdiet,butseverecasesrequiresurgicalremovalofportionsoftheprostate.Thissurgery,ifnotdoneverycarefullycanleadtoproblemswithurinationorsexualperformance.bulbourethralglandsThebulbourethralglandsorCowper’sglandsarethethirdoftheaccessorystructures.Theseareasmallpairofglandsalongtheurethrabelowtheprostate.Theirfluidissecretedjustbeforeemissionofthesemen,thusitisthoughtthatthisfluidmayserveasalubricantforinsertingthepenisintothevagina,butbecausethevolumeofthesesecretionsisverysmall,peoplearenottotallysureofthisfunction.Penis/Theurethragoesthroughthepenis.Inhumans,thepeniscontainsthreecylindersofspongy,erectiletissue.Duringarousal,t