组织学与胚胎学胚胎学

Germ disc form and differentiate胚层的形成和分化,主讲人： 苏衍萍,1、Development of the bilaminar germ disc（二胚层的形成,2w）：(1)二胚层胚盘（bilaminar germ disc)。上胚层（epiblast） 下胚层（hypoblast） 羊膜腔（amniotic cavity)， 卵黄囊(yolk sac)。,体蒂,（body stalk),(2)The amniotic cavity develops within the epiblast,(3)The formation of the yolk sac（卵黄囊形成）,初级卵黄囊,胚外中胚层的网状组织,On days 10 to 11, an acellular extraembryonic reticulum form between Heusers membrane and the cytotrophoblast.,下胚层形成次级卵黄囊,(4)The hypoblast gives rise to the extraembryonic endoderm that lines the primary yolk sac(5)The chorionic cavity is produced in conjunction with the development of the extraembryonic mesoderm(6) The definitive yolk sac is formed by a new wave of cells that migrate from the hypoblast and displace heusers membrane,2、三胚层的形成(第3周）(1)The primitive streak appears at the beginning of the third week(原条的出现,3w)原条 primitive streak原结 primitive node原凹 primitive pit 原沟 primitive groove,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： The appearance of the primitive streak establishes the longitudinal axis and thus the bilateral symmetry of the future adult and decide embryo orientation 1.确定了中轴2.确定头尾方向 3.是胚体的组织中心,(2)The definitive endoderm（内胚层） and intraembryonic mesoderm（胚内中胚层） form through the primitive streak,the ectoderm外胚层,the mesoderm中胚层,definitive endoderm内胚层,the epiblast上胚层,The primitive streak retreats and disappears, and the caudal eminence gives rise to caudal structures of the body. （15-26day ）The mechanics of gastrulation are not well understoodThe fate of gastrulation epiblast cells can be predicted from their site of origin.Study method:Cell tracing and cell lineage（细胞系） studies,(3)The notochord(脊索)is produced by cells that ingress through the primitive node,Primitive pot(原结） The Notochordal process（脊索突） the notochordal plate（脊索板） the notochord（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。The ultimate fate of the notochord is debated.Mesoderm is excluded from the buccopharyngeal and cloacal membrances.,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： neural plate 神经板 neural groove 神经沟 neural fold 神经褶 neural tube 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）This anomaly may form through defective ossification of the occipital bone and probably is not a consequence of defective closure of the neural tube.,Headless mice. The development and maintenance of the “head organizing center” requires the expression of the homeobox gene Lim-1. Knock out of Lim-1 results in headless mice.,Fig 4-12,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、mesoderm differentiate( 中胚层的分化)：（1）paraxial mesoderm(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）intermediate mesoderm(间介中胚层)位于体节外侧 ，泌尿生殖系统发生的原基。,（3）lateral plate mesoderm(侧中胚层)分两层A:Parietal mesoderm(体壁中胚层)：分化为体壁的肌肉、结缔组织、浆膜壁层。B:Ventral mesoderm(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、Endoderm differentiate (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