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1、SexDeterminationSecondaryarticleJoeLeighSimpson,BaylorCollegeofMedicine,Houston,Texas,USAArticleContents.ReproductiveEmbryologySexdeterminationistheprocessbywhichgenesdirectmaleandfemaleembryosto.SexDeterminationinMales:GenesandChromosomesbecomedisting
2、uishablefromeachother.InfluencingTesticularDifferentiation.SexDeterminationinFemales:GenesandChromosomesInfluencingOvarianDifferentiationReproductiveEmbryology.TrueHermaphroditism:AnAutosomalDisorderofGonadalDifferentiationPrimordialgermcellsoriginatei
3、ntheendodermoftheyolk.SelectedDisordersofExternalGenitalDevelopmentin46,XX:FemalePseudohermaphroditismsacandmigratetothegenitalridgetoformtheindifferent.SelectedDisordersofExternalGenitalDevelopmentingonad.Initially,46,XYand46,XXgonadsareindistin-46,XY:
4、MalePseudohermaphroditismguishable.Indifferentgonadsdevelopintotestesifthe.KlinefelterSyndrome(SeminiferousTubuleembryo,ormorespecificallythegonadalstroma,is46,XY.Dysgenesis)Thisprocessbeginsabout43daysafterconception.Testesbecomemorphologicallyidentifiab
5、le7–8weeksafterconception(9–10weeks’gestationalormenstrualweeks).Testiculardifferentiationtosteroneisthenconvertedby5a-reductasetodihydro-testosterone(DHT),anditisthishormonethatisSertolicellsarethefirstcellstobecomerecognizableinresponsibleforexternalg
6、enitaliavirilization.Theseactionstesticulardifferentiation,organizingthesurroundingcellscanbemimickedbytheadministrationoftestosteronetointotubules.LeydigcellsandSertolicellsexerttheirfemaleorcastratedmaleembryos.functionindissociationfromtesticularmorp
7、hogenesis;FetalSertolicellsproducethenonandrogenicglycopro-thus,thesecellsdirectgonadaldevelopment,ratherthanteinantimu¨llerianhormone(AMH),alsocalledmu¨lleriantheconverse.Thesetwocelltypessecretedifferentinhibitorysubstance(MIS);AMHdiffuseslocallytocaus
8、ehormones,whichinaggregatedirecttheembryotodevelopregressionofmu¨llerianderivatives(uterusandfallopianintoamale(Figure1).tubes).ThishormonemayhavefunctionsrelatedtoFetalLeydigcellsproducetestosterone,ahormonethatgonadaldevelopmentaswell
