User:Hegarty.michael.c/sandbox

Tyler Popp and I are improving the ectoderm page.

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 * clam forabettalorretta 04:18, 19 March 2013 (UTC)

Like the other two germ layers, (mesoderm and endoderm) the ectoderm forms shortly after the egg is fertilized, and rapid cell division initiates. The epidermis of the skin originates from the less dorsal ectoderm which surrounds the neural ectoderm at the early gastrula stage of embyronic development. The position of the ectoderm relative to the other germ layers of the embyro is governed by selective affinity, meaning that the inner surface of the ectoderm has a strong (positive) affinity for the mesoderm, and a weak (negative) affinity for the endoderm layer. This selective affinity for changes during different stages of development. The strength of the attraction between two surfaces of two germ layers is determined by the amount and type of cadherin molecules present on the cells' surface. For example, the expression of N-cadherin is crucial to maintaining separation of precursor neural cells from precursor epithelial cells.