Figure 4.

Schematic representation of early embryonic development. During early embryo development, the extraembryonic mesoderm and the exocoelomic cavity (EC) relate the trophoblast (T) to the amnion and the secondary yolk sac (YS). The existence of two extra-embryonic axes, an exocoelomic-amniotic axis and a trophoblastic-yolk sac axis could be proposed. This would enable the formation of the intraembryonic mesenchymal since they are integrated. These extraembryonic functions are expressed by the host organism when it suffers an injury and focuses on the injured tissue or organ. After these functions are incorporated by the injured tissue or organ, this said tissue or organ acquires the embryonic functional autonomy needed to successfully repair itself. A: amnion; EC: exocoelomic cavity; EM: extraembryonic mesoderm; D: decidua; T: trophoblast; YS: secondary yolk sac.