Developmental Biology 第二章胚胎的早期发育
Developmental Biology 第二章 胚胎的早期发育
Developmental Biology 5059035 代8888 Fish Salamander Tortoise Chick Ho Calf Rabbit Human
Developmental Biology
Developmental Biology 、卵裂 Cleavage ()、卵裂的特点 卵裂期是指受精卵开始有丝分裂并产生由较小的细胞构 成的囊胚( blastula)的过程。 卵裂的主要特点包括: 分裂周期短; 分裂球的体积下降:海胆胚胎的质/核比由550降至6; 早期卵裂中合子基因大多处于休眠状态; 卵裂常经历由均等裂向不均等裂变化
Developmental Biology (一)、卵裂的特点 卵裂期是指受精卵开始有丝分裂并产生由较小的细胞构 成的囊胚(blastula)的过程。 卵裂的主要特点包括： 分裂周期短; 分裂球的体积下降：海胆胚胎的质/核比由550降至6; 早期卵裂中合子基因大多处于休眠状态； 卵裂常经历由均等裂向不均等裂变化。 一、卵裂 Cleavage
Developmental Biology (二)、卵裂的类型 经线裂( meridional cleavage):指卵裂面 与A一V轴平行的卵裂方式。 纬线裂( equatorial cleavage):指卵裂面与 A-V轴垂直的卵裂方式
Developmental Biology (二)、卵裂的类型 经线裂(meridional cleavage):指卵裂面 与A－V轴平行的卵裂方式。 纬线裂(equatorial cleavage):指卵裂面与 A－V轴垂直的卵裂方式
Developmental Biology Radial辐射型:海鞘、海胆、两栖类 Spira螺旋型:螺、蚌、软体动物、 Holoblastic全卵裂 纽形动物、多毛类动物 Rationa旋转型:哺乳动物 卵裂类型 Discoidal盘状偏裂:鸟类、鱼类等端 Meroblastic偏裂 黄和极端端黄卵 Superficial表面裂中黄卵(昆虫)
Developmental Biology Holoblastic 全卵裂 Radial 辐射型: 海鞘、海胆、两栖类 Rational 旋转型:哺乳动物 Spiral 螺旋型: 螺、蚌、软体动物、 纽形动物、多毛类动物 Discoidal 盘状偏裂：鸟类、鱼类等端 黄和极端端黄卵 Meroblastic 偏裂 Superficial 表面裂:中黄卵(昆虫) 卵裂类型
Developmental Biology 辐射型全卵裂 海鞘:经一经一纬一经…,8次分裂后产生的256细胞 柱形胚胎在两极细胞移动封口后成为中空柱形囊胚。 Meridional Animal polecleavage Equatorial ne deava age pLane Figure 5.2 Holoblastic cleavage in the echinoderm Synapta digita, leading to the formation of a hollow blastula, as shown in the cutaway view in the last panel (After Vegetal pole Saunders, 1982) Hollow blastula (cut ope
Developmental Biology 辐射型全卵裂 海鞘：经－经－纬－经……，8次分裂后产生的256细胞 柱形胚胎在两极细胞移动封口后成为中空柱形囊胚
Dev 海胆:第四次分裂后将开始不均等分裂,第7次分裂后产生128细胞 组成的囊胚( see next slide).植物极的 micromeres是生骨中胚层命运,具 有起动原肠作用、诱导第二胚轴的活性。 (A) igure 5.3 Animal pole Cleavage in the sea urchin. (A) Planes of cleavage in the first three divisions and the formation of particular tiers of cell in divisions 3-6(B-D) Photomicro graphs of live embryos of the sea urchin Lytechinus pictus, looking down upon the animal pole. (B) The 2-cell stage. (C) The 4-cell stage. (D) The 32-cell stage, shown without the fertilization mem. Vegetal pole brane to allow visualization of the ani- mal pole mesomeres, the central Animal Meso macromeres, and the vegetal micro- derived meres, which angle into the center (Photographs courtesy of G derived Watchmaker. half Micromeres Macromeres (D)
Developmental Biology 海胆：第四次分裂后将开始不均等分裂，第7次分裂后产生128细胞 组成的囊胚(see next slide). 植物极的micromeres是生骨中胚层命运，具 有起动原肠作用、诱导第二胚轴的活性
Developmental Biology 海胆早期囊胚的细胞体积一致,其后长出纤毛,使囊胚可 在受精膜内转动,同时也因细胞的增殖,细胞变瘪。 囊胚腔形成的2种可能机制:a,卵裂球分泌的蛋白进入囊胚 腔中,导致腔中液体粘稠而吸取胚外水分,腔内的膨胀压阻止 了细胞向腔内增生;b,细胞与受精膜内的透明层紧密粘接, 使细胞不能向腔内增生 囊胚的孵化:由动物极细胞分泌孵化酶降解受精膜。 - Cilium 日 Blastocoel (A)Young blastula (B)Older blastula with flattened vegetal plate and ciliary tuft Figure 5.5 Sea urchin blastulae. (A)Sketch of a control cross-section through an early sea urchin blastula, showing a single layer of rounded cells surrounding a large blasto- coel. ( B)As division continues, the cells of the late blastula show differences in shape as the vegetal plate cells elongate. (C)Tight junctions(arrow) forming between cells of a 1024-cell echinoderm blastula. (A and B after Giudice, 1973; C from Dan-Sohkawa and Fujisawa, 1980, courtesy of the authors
Developmental Biology 海胆早期囊胚的细胞体积一致，其后长出纤毛，使囊胚可 在受精膜内转动，同时也因细胞的增殖，细胞变瘪。 囊胚腔形成的2种可能机制：a, 卵裂球分泌的蛋白进入囊胚 腔中，导致腔中液体粘稠而吸取胚外水分，腔内的膨胀压阻止 了细胞向腔内增生；b, 细胞与受精膜内的透明层紧密粘接， 使细胞不能向腔内增生。 囊胚的孵化：由动物极细胞分泌孵化酶降解受精膜
Developmental Biology 蛙类:卵黄对卵裂的阻碍作用导致卵裂沟延伸缓慢、第 三次纬裂发生不均等分裂。植物极半球分裂的速度始终较 慢,所以囊胚的植物极细胞较大。 Figure 5.7 begins in the animal region of the egg Cleavage of a frog egg Cleavage fur- before the first division has divided the rows,designated by roman numerals, aIs, vegetal cytoplasm. (C) The third div are numbered in order of appearance sion is displaced toward the animal (A, B)The vegetal yolk impedes the ole (D-H)The vegetal hemisphere cleavage such that the second division ultimately contains longer and fewer blastomeres than the animal half (B) lⅡ Ⅱ Ⅲ
Developmental Biology 蛙类：卵黄对卵裂的阻碍作用导致卵裂沟延伸缓慢、第 三次纬裂发生不均等分裂。植物极半球分裂的速度始终较 慢，所以囊胚的植物极细胞较大
Developmental Biology (A) Cleavage Figure 5.8 anning electron micrographs of the cleavage of a frog egg. (A) First cleavage,(B) cy between the animal and vegetal cells after arising from the third division (A'n Second cleavage (4 cells). (C)Fourth cleavage (16 cells), showing the size discrepa from Beams and Kessel, 1976, courtesy of the authors: B and C courtesy of L. Biedler)
Developmental Biology