England M A, Wakely J
Anat Embryol (Berl). 1977 May 12;150(3):291-300. doi: 10.1007/BF00318347.
The distribution of mesoderm, the structure of mesoderm cells and relationship between mesoderm and ectoderm were examined by SEM in embryos at stages 3 to 5. The mesoderm was displayed by removal of the endoderm and by fracturing the embryos through mesoderm containing regions. Within the mesoderm layer four zones could be distinguished by their cell shape and arrangement--the primitive streak, a multilayered compact area around the margins of the area pellucida, multilayered and loosely arranged cells near the primitive streak and a flattened monolayer of cells around the advancing lateral and anterior edges of the mesoderm sheet. Secretion of basement membrane by the ectoderm was seen to precede the arrival of mesoderm cells. This suggests that ectoderm alone can synthesize basement membrane without mesodermal contribution.
在第3至5阶段的胚胎中，通过扫描电子显微镜（SEM）检查了中胚层的分布、中胚层细胞的结构以及中胚层与外胚层之间的关系。通过去除内胚层并通过含有中胚层的区域对胚胎进行断裂来显示中胚层。在中胚层内，可以根据细胞形状和排列区分出四个区域——原条、透明带边缘周围的多层致密区域、原条附近多层且排列松散的细胞以及中胚层片层前进的外侧和前缘周围的扁平单层细胞。观察到外胚层分泌基底膜先于中胚层细胞的到达。这表明外胚层单独就能合成基底膜，而无需中胚层的参与。
