Watt J M, Petitte J N, Etches R J
Department of Animal and Poultry Science, University of Guelph, Ontario, Canada.
J Morphol. 1993 Feb;215(2):165-82. doi: 10.1002/jmor.1052150205.
The ultrastructure of the early chick embryo was investigated, using scanning (SEM) and transmission electron microscopy (TEM). Eggs were obtained from the shell gland by injecting hens intravenously with a synthetic prostaglandin or arginine vasopressin. Embryos were examined during late cleavage (stages IV-VI, Eyal-Giladi and Kochav, '76), formation of the area pellucida (stages VII-XI), and formation of the hypoblast (stages X-XIV). SEM highlighted the reduction in cell number at the underside of the embryo during formation of the area pellucida although it became apparent that the thickness of the embryo is not reduced to a single layer of cells at stage X. In addition, blastomeres at the perimeter of embryos (stages V-VI) project filopodial extensions onto a smooth membrane that separates the sub-embryonic cavity from the yolk. During hypoblast formation, epiblast cells generate stellate projections at their basal aspect, thus providing a meshwork for the advancing secondary hypoblast cells. By stage XII the epiblast was one cell thick and reminiscent of a columnar epithelium when viewed transversely. Cells of the deep portion of the posterior marginal zone were distinguished morphologically in the stage XII embryo by their many cell surface projections and ruffled appearance. Blastomeres at the perimeter of stage V-VI embryos projected filopodial extensions onto a smooth membrane which separates the sub-embryonic cavity from the yolk. This membrane is presumed to be confluent with the cytolemma. Evidence is presented demonstrating the presence of intracellular membrane-bound droplets which are hypothesised to contain sub-embryonic fluid.
利用扫描电子显微镜（SEM）和透射电子显微镜（TEM）对早期鸡胚的超微结构进行了研究。通过给母鸡静脉注射合成前列腺素或精氨酸加压素，从壳腺获取鸡蛋。在晚期卵裂阶段（IV-VI期，Eyal-Giladi和Kochav，1976年）、明区形成阶段（VII-XI期）和成下胚层阶段（X-XIV期）对胚胎进行检查。SEM突出显示了明区形成过程中胚胎底部细胞数量的减少，尽管很明显在X期胚胎厚度并未减至单层细胞。此外，胚胎周边的卵裂球（V-VI期）将丝状伪足延伸投射到将胚下腔与卵黄分隔开的光滑膜上。在下胚层形成过程中，上胚层细胞在其基部产生星状突起，从而为前进的次级下胚层细胞提供了一个网络。到XII期时，上胚层为单层细胞，横向观察时类似柱状上皮。在XII期胚胎中，后缘区深部的细胞通过其许多细胞表面突起和褶皱外观在形态上得以区分。V-VI期胚胎周边的卵裂球将丝状伪足延伸投射到将胚下腔与卵黄分隔开的光滑膜上。该膜被认为与细胞膜相连。有证据表明存在细胞内膜结合小滴，推测其含有胚下液。
