NATS 1610 Lecture Notes - Inner Cell Mass, Embryonic Disc, Nissan L Engine
5 Feb 2014
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Document Summary
Embryonic period: extends from the 3rd to the 8th week, pre-embryo now called an embryo, period of morphogenesis. Tissues and organs form: by the end of the embryonic period distinct human appearance. Gastrulation begins the process by which the developing embryo"s (gastrula) body takes shape and becomes organized: during implantation, inner cell moves from surface of blastocyst. Inner cell mass flattens plate like structure embryonic disk becomes embryo: amniotic cavity forms lined by amnion filled with amniotic fluid. Cells of embryonic disk differentiate (change & specialize) & migrate inward: forming 3 primary germ layers ectoderm, mesoderm, endoderm. Day 4 morula: solid ball of cells formed as the zygote undergoes cleavage. Day 6 early blastocyst: hollow ball of cells with a fluid-filled cavity. Day 10 late blastocyst: pre-embryo, with the embryonic disk, two layers of cells that become the embryo proper. Day 16 gastrula: embryo with three primary germ layers (ectoderm, mesoderm, and endoderm)
