embryonic structure 胚胎结构 epiblast (generic) 外胚层（通用） In amniote animal embryology, the epiblast is a tissue type derived either from the inner cell mass in mammals or the blastodisc in birds and reptiles. It lies above the hypoblast. In mammalian embryogenesis, the columnar cells of the epiblast are adjacent to the trophoblast, while the cuboidal cells of the hypoblast are closer to the blastocoele. The epiblast, whilst referred to as the primary ectoderm, differentiates to form all three layers of the trilaminar germ disc in a process called gastrulation[WP]. The outer of the two layers of the blastoderm that form during gastrulation, corresponding to primitive ectoderm during gastrulation and to the definitive ectoderm after gastrulation[ZFA] blastocyst ectoblast epiblast epiblastus primitive ectoderm 原始外胚层 在羊膜动物胚胎学中，外胚层是来源于哺乳动物内细胞团或鸟类和爬行动物胚盘的组织类型。它位于下胚层的上方。在哺乳动物胚胎发生中，外胚层的柱状细胞与滋养层毗邻，而下胚层的立方细胞更接近胚泡。外胚层虽然被称为初级外胚层，但在称为原肠胚形成的过程中分化形成三胚层的所有三层结构[WP]。原肠胚形成期间形成的胚层的两层外层，对应于原肠胚形成期间的原始外胚层和原肠胚形成后的明确的外胚层[ZFA] 外胚叶 外胚层(ectoblast) 外胚层(epiblast) 胚泡