Gastrulation, 3rd week

Gastrulation, 3rd week

1. epiblast

   • source of all of the germ layers. Cells in these layers will give rise to all of the tissues and organs in the embryo
   • primitive streak
     • primitive node
       • cephalic end of the streak. Slightly elevated area surrounding the primitive pit
       • prenotochordal cells
         • invaginate in the primitive node
         • prechordal plate
           • notochordal plate
             • detachment from the endoderm
               • notochord
     • invagination
       • cells detach from the epiblast and slip beneath it. Cell migration and specification are controlled by fibroblast growth factor 8 (FGF8)
       • endoderm
         • cells that displace the hypoblast
         • form AVE which expresses- head-forming genes
           • OTX2
           • LIM1
           • HESX1
       • mesoderm
         • cells that lie between the epiblast and newly created endoderm
       • ectoderm
         • cells that remain in the epiblast