The mesoderm migrates anteriorly and laterally between the endoderm and the epiblast. It becomes a morula, then an early blastocyst, and then a late blastocyst. The blastocyst enters the uterus, hatches from the zona pellucida and begins to implant on day 6. The primitive streak is beginning to form by days 13-14, and the streak is still elongating on day 15 when the first menstrual period is missed. The human primitive streak is much like that of the chick.
Human gastrulation uses convergence-extension and ingression.
Each cell of the embryo is thus presumed to have the same genetic endowment. This site maintained by the Life Sciences Web Team .