outer cell mass trophoblast supporting structures Week Two blastula implants

Outer cell mass trophoblast supporting structures

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outer cell mass   trophoblast (supporting structures) Week Two blastula implants into uterus (~50% chance) embryoblast dvides into two layers: o epiblast  (on top): future embryo o hypoblast  (below): future yolk sac how does epiblast become the entire organism?? GASTRULATION  – “most important event in life”
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************** gastrulation:  formation of the three germ layers (cell lineages) common to all animals a process of migration and differentiation cells in midline of epiblast dive downwards and spread out as they migrate, they from new layers: o mesoderm o endoderm the epiblast layer is now called the ectoderm view gastrulation from top, see  primitive streak  grow from the caudal (tail)  end toward the middle o ectodermal cells tall and columnar o mesodermal cells connective tissue o endodermal cells – lining cells in vertebrates (actually chordates), another important exciting event:  o notochord:  stiffened rod of mesoderm; future “core” of axial skeleton After three weeks: a three-layered, elongated disk attached to the uterus (inside a sac – the  amnion) Germ Layer Derivatives ectoderm: o epidermis, nervous system, neural crest cells, eyes, ears, nose (most  of head)
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endoderm: o digestive, respiratory, most of endocrine mesoderm: o skeletal tissue, muscle, circulatory, lymph, reproductive system How do you make a body from three stem cell lines?
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  • Spring '08
  • GeorgeV.Lauder,AndrewA.Biewener,PeterT.Ellison,andDanielE.Lieberman
  • Developmental Biology, cells, Neural tube, Mesoderm, neural crest cells

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