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Unformatted text preview: o The blastocyst implants into the uterus about 7 days after fertilization. o The embryonic portion of the placenta is derived from the trophoblast of the blastocyst. Formation of the Germ Layers o The embryo forms around the primitive streak, which forms about 14 days after fertilization. o All tissues of the body are derived from three primary germ layers: ectoderm, mesoderm, and endoderm. Neural Tube and Neural Crest Formation o The nervous system develops from a neural tube that forms in the ectodermal surface of the embryo and from neural crest cells derived from the developing neural tube....
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- Fall '10