Editing Morphogenesis (section)

===Cell contractility===
Tissues can change their shape and separate into distinct layers via cell contractility. Just as in muscle cells, [[myosin]] can contract different parts of the cytoplasm to change its shape or structure. Myosin-driven contractility in embryonic tissue morphogenesis is seen during the separation of [[germ layer]]s in the [[model organism]]s ''[[Caenorhabditis elegans]]'', ''[[Drosophila]]'' and [[zebrafish]]. There are often periodic pulses of contraction in embryonic morphogenesis. A model called the cell state splitter involves alternating cell contraction and expansion, initiated by a bistable organelle at the apical end of each cell. The organelle consists of [[microtubule]]s and [[microfilament]]s in mechanical opposition. It responds to local mechanical perturbations caused by morphogenetic movements. These then trigger traveling [[embryonic differentiation waves]] of contraction or expansion over presumptive tissues that determine cell type and is followed by cell differentiation. The cell state splitter was first proposed to explain [[neural plate]] morphogenesis during [[gastrulation]] of the [[axolotl]]<ref>{{Cite journal | doi=10.1007/BF02797122| pmid=2450659|title = The cytoskeletal mechanics of brain morphogenesis| journal=Cell Biophysics| volume=11| pages=177–238|year = 1987|last1 = Gordon|first1 = Richard| last2=Brodland| first2=G. Wayne| s2cid=4349055}}</ref> and the model was later generalized to all of morphogenesis.<ref>{{Cite journal | doi=10.1186/s12976-016-0037-2| pmid=26965444| pmc=4785624|title = The organelle of differentiation in embryos: The cell state splitter| journal=Theoretical Biology and Medical Modelling| volume=13| pages=11|year = 2016|last1 = Gordon|first1 = Natalie K.| last2=Gordon| first2=Richard| doi-access=free}}</ref><ref>{{Cite book | doi=10.1142/8152|title = Embryogenesis Explained|year = 2016|last1 = Gordon|first1 = Natalie K.| last2=Gordon| first2=Richard| isbn=978-981-4350-48-8}}</ref>