组织学与胚胎学-胚胎学2

Germdiscformanddifferentiate胚层的形成和分化,主讲人：苏衍萍,1、Developmentofthebilaminargermdisc（二胚层的形成,2w）：(1)二胚层胚盘（bilaminargermdisc)。上胚层（epiblast）下胚层（hypoblast）羊膜腔（amnioticcavity)，卵黄囊(yolksac)。,体蒂,（bodystalk),(2)Theamnioticcavitydevelopswithintheepiblast,(3)Theformationoftheyolksac（卵黄囊形成）,初级卵黄囊,胚外中胚层的网状组织,Ondays10to11,anacellularextraembryonicreticulumformbetweenHeusersmembraneandthecytotrophoblast.,下胚层形成次级卵黄囊,(4)Thehypoblastgivesrisetotheextraembryonicendodermthatlinestheprimaryyolksac(5)Thechorioniccavityisproducedinconjunctionwiththedevelopmentoftheextraembryonicmesoderm(6)Thedefinitiveyolksacisformedbyanewwaveofcellsthatmigratefromthehypoblastanddisplaceheusersmembrane,2、三胚层的形成(第3周）(1)Theprimitivestreakappearsatthebeginningofthethirdweek(原条的出现,3w)原条primitivestreak原结primitivenode原凹primitivepit原沟primitivegroove,两胚层胚盘背面观,口咽膜,胚盘,脊索突,原结,原条,泄殖腔膜,中胚层,Significance：Theappearanceoftheprimitivestreakestablishesthelongitudinalaxisandthusthebilateralsymmetryofthefutureadultanddecideembryoorientation1.确定了中轴2.确定头尾方向3.是胚体的组织中心,(2)Thedefinitiveendoderm（内胚层）andintraembryonicmesoderm（胚内中胚层）formthroughtheprimitivestreak,theectoderm外胚层,themesoderm中胚层,definitiveendoderm内胚层,theepiblast上胚层,Theprimitivestreakretreatsanddisappears,andthecaudaleminencegivesrisetocaudalstructuresofthebody.（15-26day）ThemechanicsofgastrulationarenotwellunderstoodThefateofgastrulationepiblastcellscanbepredictedfromtheirsiteoforigin.Studymethod:Celltracingandcelllineage（细胞系）studies,(3)Thenotochord(脊索)isproducedbycellsthatingressthroughtheprimitivenode,Primitivepot(原结）TheNotochordalprocess（脊索突）thenotochordalplate（脊索板）thenotochord（脊索),意义：决定胚体中轴诱导外胚层形成神经板椎间盘中髓核。Theultimatefateofthenotochordisdebated.Mesodermisexcludedfromthebuccopharyngealandcloacalmembrances.,小结：胚胎发育：第一周：植入第二周：二胚层第三周：三胚层,第四周：圆柱体,四、三胚层的分化,1、外胚层的分化（1）神经管形成：neuralplate神经板neuralgroove神经沟neuralfold神经褶neuraltube神经管脑、脊髓前神经孔未闭无脑儿后神经孔未闭脊髓裂脊柱裂,Meningohydroencephalocele(脑积水脑膜脑突出）Thisanomalymayformthroughdefectiveossificationoftheoccipitalboneandprobablyisnotaconsequenceofdefectiveclosureoftheneuraltube.,Headlessmice.Thedevelopmentandmaintenanceofthe“headorganizingcenter”requirestheexpressionofthehomeoboxgeneLim-1.KnockoutofLim-1resultsinheadlessmice.,Fig4-12,小结：神经系统、脑垂体、松果体、皮肤：表皮、附属结构凹陷上皮：口、鼻、肛门、外耳道、膜迷路、角膜上皮、视网膜、晶状体肾上腺髓质、腮腺上皮,(2)神经嵴周围神经系统肾上腺髓质,分化,外胚层分化,(3)表面外胚层:皮肤表皮及其附属器,2、mesodermdifferentiate(中胚层的分化)：（1）paraxialmesoderm(轴旁中胚层)(somites)体节，第5周全部形成，共42-44对，分化为真皮，大部分中轴骨和骨骼肌。（2）intermediatemesoderm(间介中胚层)位于体节外侧，泌尿生殖系统发生的原基。,（3）lateralplatemesoderm(侧中胚层)分两层A:Parietalmesoderm(体壁中胚层)：分化为体壁的肌肉、结缔组织、浆膜壁层。B:Ventralmesoderm(脏壁中胚层)：分化为内脏平滑肌、结缔组织和浆膜脏层。胚内体腔：形成体腔。,体节,21天,3、Endodermdifferentiate(内胚层的分化)：随胚体的卷曲，内胚层形成原始消化管，,内胚层：是消化系统、呼吸系统和中耳、甲状腺、甲状旁腺、扁桃体、胸腺，膀胱和尿道等上皮的原基。,五、胚胎外形的建立及演变1、胚体的形成,三周三胚层，体节神经兆。四周圆筒状，头大尾尖小，外形似豆芽，头尾腹侧靠。,五周鳃弓全，视杯与听泡。,六周手指见，耳廓小苗苗。,七周体伸直，颜面形成了。八周成人形，肢体头面俏。,三月分男