Organogenesis Ectoderm

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ectodermal specification


all of organs rise ectoderm such nervous system, teeth, hair , many exocrine glands, originate 2 adjacent tissue layers: epithelium , mesenchyme.


several signals mediate organogenesis of ectoderm such as: fgf, tgfβ, wnt, , regulators hedgehog family. specific timing , manner ectodermal organs form dependent on invagination of epithelial cells. fgf-9 important factor during initiation of tooth germ development. rate of epithelial invagination in increased action of fgf-9, expressed in epithelium, , not in mesenchyme. fgf-10 helps stimulate epithelial cell proliferation, in order make larger tooth germs. mammalian teeth develop ectoderm derived mesenchyme: oral ectoderm , neural crest. epithelial components of stem cells continuously growing teeth form tissue layers called stellate reticulum , suprabasal layer of surface ectoderm.








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