In utero, the blastocyst implants and all three embryonic germ layers are formed during gastrulation. Somatic stem cells are present in many fetal and post-natal tissues. Somatic stem cells are ...

which forms a blastocyst. This structure implants around one week after fertilization. As development continues, the epiblast invades inward toward the primitive endoderm. This begins the ...

The outer membrane (chorion) and trophoblast layer of the placenta are derived from the trophoectoderm of the blastocyst cells. Other extra-embryonic tissues, including the amnion (inner membrane ...