The layer of tissue that forms the wall of the blastocyst in the early stages of embryonic development. The trophectoderm helps to implant the blastocyst to the uterine wall and supplies nutrients to the embryo. During implantation, the trophectoderm differentiates into two layers. The inner layer, the cytotrophoblast forms into the chorion. The outer layer, syncytiotrophoblast, develops into the outer layer of the placenta. The trophectoderm is also known as the trophoblast.
Group of cells that differentiates around the periphery of the developing embryo when it is a blastocyst and which will, if all goes well after implantation, form the placenta and membranes. See also: inner cell mass See also: trophoblast