Technical and ethical limitations create a challenge to study early human development, especially following the first 3 weeks of development after fertilization, when the fundamental aspects of the body plan are established through the process called gastrulation. As a consequence, our current understanding of human development is mostly based on the anatomical and histological studies on Carnegie Collection of human embryos, which were carried out more than half a century ago. Due to the 14-day rule on human embryo research, there have been no experimental studies beyond the fourteenth day of human development. Mutagenesis studies on animal models, mostly in mouse, are often extrapolated to human embryos to understand the transcriptional regulation of human development. However, due to the existence of significant differences in their morphological and molecular features as well as the time scale of their development, it is obvious that complete knowledge of human development can be achieved only by studying the human embryo. These studies require a cellular framework. Here we summarize the cellular, molecular, and temporal aspects associated with human gastrulation and discuss how they relate to existing human PSCs based models of early development.

技术和伦理限制为研究早期人类发育带来了挑战，特别是在受精后的前 3 周发育之后，此时身体计划的基本方面是通过称为原肠胚形成的过程建立的。因此，我们目前对人类发育的理解主要基于半个多世纪前对卡内基人类胚胎收藏进行的解剖学和组织学研究。由于人类胚胎研究的 14 天规则，在人类发育的第 14 天之后没有任何实验研究。动物模型的诱变研究，主要是在小鼠身上，通常会外推到人类胚胎，以了解人类发育的转录调控。然而，由于它们的形态和分子特征以及它们发育的时间尺度存在显着差异，显然只有通过研究人类胚胎才能获得对人类发育的完整认识。这些研究需要一个细胞框架。在这里，我们总结了与人类原肠胚形成相关的细胞、分子和时间方面，并讨论它们如何与现有的基于人类 PSC 的早期发育模型相关。