Animal Science 434Reproductive PhysiologyLec 5: Embryogenesis of the Pituitary andSexual DevelopmentDevelopment of the Pituitary GlandStomodeumRathke’s PouchInfundibulumBrainMigration begins by the 4 week of gestation in cow and human.Germ Cell MigrationMigration from endodermthrough mesoderm.In birds the migration is via the blood stream.Fetal Kidneys• Pronephros» regresses• Mesonephros» portions of reproductive tract• Metenephros» Adult kindney and urinary ductsDevelopment of Mesenephros and MetenephrosDevelopment of Mesenephros and MetenephrosEarly Development Flash Moviehttp://www.ansci.wisc.edu/jjp1/as4 34/powerpoint/fa07/early_dev.swfRequires the free flash player which can be downloadedfrom: www.adobe.comJost ExperimentsMesonephric Ducts(Wolffian Ducts)Mesonephric Ducts(Wolffian Ducts)Paramesonephric Ducts(Mullerian Ducts)TestisEpididymisEpididymisVas DeferensSeminalVesiclesOvaryOviductUterusSex Determination: The Jost ParadigmChromosomal SexGonadal SexPhenotypic SexSex Determination: The Jost ParadigmChromosomal SexGonadal SexPhenotypic SexChromosomal SexGonadal SexPhenotypic SexHormonal SexBrain and/or Behavioral SexChromosomal Sex• Single Pair of sex chromosomes» mammals, some but not all vertebrates• Sex is environmentally determined» sea worms, fish, reptiles• Multiple sex chromosomes» invertebrates, insects, reptiles• Haplodiploidy» bees, spidersChromosomal SexA. Drosophila• Sex depends on the number of X chromosomes– X or XY or XO = Male– XX or XXX or XXY = FemaleChromosomal SexA. Drosophila• Sex depends on the number of X chromosomes– X or XY or XO = Male– XX or XXX or XXY = FemaleB. Human (mammals)• XY or XXY or XXYY or XXXY = Male (testis)• XX or XXX = Female (ovary)• XO = Female with incomplete ovarian development• XXY or XXYY or XXXY or XXXXY = testis butimpaired sperm productionChromosomal SexA. Drosophila• Sex depends on the number of X chromosomes– X or XY or XO = Male– XX or XXX or XXY = FemaleB. Human (mammals)• XY or XXY or XXYY or XXXY = Male (testis)• XX or XXX = Female (ovary)• XO = Female with incomplete ovarian development• XXY or XXYY or XXXY or XXXXY = testis butimpaired sperm productionC. Conclusion• The gene that controls testicular differentiation ison the Y chromosome in mammals.Human X and Y ChromosomesYXThe Y ChromosomeA. Region coding for testicular development–H-Y Antigen« no longer believed to be involved–SRY« Codes for a DNA binding protein« acts as a transcription factor« Causes• primary sex chord (seminiferous tubule) development• Development of Sertoli Cells• Anti-Mullerian Hormone production by Sertoli Cells« absence of SRY• 2nd sex chords (egg nests) develop• Short arm of Y chromosomeThe Y Chromosome Cont.B. Other genes on the Y chromosome» Spermatogenesis» androgen production» long bone growthSRY and Birds• Birds» females ZW, males ZZ» W chromosome determines sex» SRY is found on the Z chromosome !• SRY is not the only sex determining gene inanimalsGonadal SexTestis Determining Factor(SRY gene product)XY MaleTestes developRete TubulesUndifferentiated Sex ChordsMullerian DuctMesonephric Duct(Wolffian Duct)Tunica AlbugineaMesonephric TubulesTesticular DevelopmentRete TubulesPrimary, Epithelial orMedullary Sex Chords• Primordial germ cells (gonocytes)• Pre-Sertoli CellsMullerian DuctWolffian DuctTunica AlbugineaMesonephric TubulesPrimary Sex Chords in Fetal TestisGonocytePre-SertoliHormonal SexTestis Determining Factor(SRY gene product)Testes developXY MaleSertoli cells secreteanti-mullerian hormone (AMH)AMH causes leydigcells to differentiateTestosteroneDevelopment of maleduct systemTestisTTNucleusTRWolffian Duct CellsRete TubulesSeminiferousTubulesVasDeferensTunica AlbugineaEfferent Ducts(Vas Efferentia)EpididymisTestis Determining Factor(SRY gene product)Testes developXY MaleSertoli cells secreteanti-mullerian hormone (AMH)AMH causes leydigcells to differentiateTestosteroneDevelopment of maleduct systemDegeneration of Mullerian ductVas efferentiaFemale DevelopmentXX FemaleNo TDFOvaries DevelopNo AMHMullerian ducts becomethe oviducts, uterus, cervix and part of the vaginaTestes Determining FactorNoTestosteroneWolffian DuctsRegressMullerianDuctPrimary or EpithelialSex ChordsWolffianDuctRegressingTubulesFuture OvarianCortexOvarianDevelopmentMullerianDuctRegressingEpithelialSex ChordsRegressingWolffianDuctRegressingTubulesFuture OvarianCortexMullerianDuctRegressingEpithelialSex ChordsRegressingWolffianDuctRegressingTubulesFuture OvarianCortexPrimordialFolliclesSecondary orCortical SexChords(egg nests)MullerianDuctRegressingWolffianDuctOvarianCortexPrimordialFolliclesOvarianMedulla2nd Sex Chords in Fetal OvaryDevelopmentof the Uterus, Cervixand VaginaMullerian DuctFused MullerianDuctHymenOvaryRegressingWolffian DuctMullerianDuctBroad Ligament Development(transverse anterior section)Reproductive tract develops outside theperitoneum!OvaryRegressingWolffianDuctMullerianDuctRegressingWolffianDuctMullerianDuctGenital Fold(Future Broad Ligament)(Posterior Transverse Section)Testis Determining Factor(SRY gene product)Testes developSertoli cells secreteanti-mullerian hormone (AMH)AMH causes leydigcells to differentiateDegeneration of Mullerian ductTestosteroneDevelopment of maleduct systemXY MaleNo TDFOvaries DevelopNo AMHMullerian ductsbecomethe oviducts,uterus, cervixand part of thevaginaXX FemaleNoTestosteroneDegeneration of Wolffian ductPhenotypic SexTestis Determining Factor(SRY gene product)Testes developSertoli cells secreteanti-mullerian hormone (AMH)AMH causes leydigcells to differentiateDegeneration of Mullerian DuctTestosteroneDevelopment of maleduct systemXY MaleTestis Determining Factor(SRY gene product)Testes developSertoli cells secreteanti-mullerian hormone (AMH)AMH causes leydigcells to differentiateDegeneration of Mullerian DuctTestosteroneDevelopment of maleduct systemXY MaleDihydrotestosteroneDevelopment of penisscrotum and accessory sex glandsTestisTTNucleusTRWolffian Duct CellsTestisTT5α -ReductaseDNucleusDRAccessory Sex Glands* and ExternalGenitalia Cells*Prostate, Cowper’s GlandSignificance of DHT• Androgen receptor has a higher affinityfor DHT• Can get effects with low levels ofcirculating testosterone• Secondary sex characteristic tissue inthe male expresses 5α-reductaseExternal Genitalia DifferentiationTestis Determining Factor(SRY gene product)Testes developSertoli cells secreteanti-mullerian hormone
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