资源描述：
《sex determination》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。
1、SexDeterminationSecondaryarticleJoeLeighSimpson,BaylorCollegeofMedicine,Houston,Texas,USAArticleContents.ReproductiveEmbryologySexdeterminationistheprocessbywhichgenesdirectmaleandfemaleembryosto.SexDeterminationinMales:GenesandChromosomesbecomedistinguishablefromeac
2、hother.InfluencingTesticularDifferentiation.SexDeterminationinFemales:GenesandChromosomesInfluencingOvarianDifferentiationReproductiveEmbryology.TrueHermaphroditism:AnAutosomalDisorderofGonadalDifferentiationPrimordialgermcellsoriginateintheendodermoftheyolk.Selected
3、DisordersofExternalGenitalDevelopmentin46,XX:FemalePseudohermaphroditismsacandmigratetothegenitalridgetoformtheindifferent.SelectedDisordersofExternalGenitalDevelopmentingonad.Initially,46,XYand46,XXgonadsareindistin-46,XY:MalePseudohermaphroditismguishable.Indifferent
4、gonadsdevelopintotestesifthe.KlinefelterSyndrome(SeminiferousTubuleembryo,ormorespecificallythegonadalstroma,is46,XY.Dysgenesis)Thisprocessbeginsabout43daysafterconception.Testesbecomemorphologicallyidentifiable7–8weeksafterconception(9–10weeks’gestationalormenstrualwe
5、eks).Testiculardifferentiationtosteroneisthenconvertedby5a-reductasetodihydro-testosterone(DHT),anditisthishormonethatisSertolicellsarethefirstcellstobecomerecognizableinresponsibleforexternalgenitaliavirilization.Theseactionstesticulardifferentiation,organizingthesurr
6、oundingcellscanbemimickedbytheadministrationoftestosteronetointotubules.LeydigcellsandSertolicellsexerttheirfemaleorcastratedmaleembryos.functionindissociationfromtesticularmorphogenesis;FetalSertolicellsproducethenonandrogenicglycopro-thus,thesecellsdirectgonadaldev
7、elopment,ratherthanteinantimu¨llerianhormone(AMH),alsocalledmu¨lleriantheconverse.Thesetwocelltypessecretedifferentinhibitorysubstance(MIS);AMHdiffuseslocallytocausehormones,whichinaggregatedirecttheembryotodevelopregressionofmu¨llerianderivatives(uterusandfallopianint
8、oamale(Figure1).tubes).ThishormonemayhavefunctionsrelatedtoFetalLeydigcellsproducetestosterone,ahormonethatgonadaldevelopmentaswell
