Embryo, 40th day
The embryo measures about 8mm. The embryogenesis is the period of embryogeny that includes the impregnation of the egg cell, blastulation, gastrulation, all of which lead to the formation of the organ structures and cause a significant change of the shape of the embryoblast and embryo. The development in the germinal period starts as a zygote that becomes a blastocyst, that on the 5th or 6th day of development nidates into the uterine mucosa. The embryonal period starts with the formation of chorionic villi and the connection to the maternal blood circulation.