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BIOL 110 (57)


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University of Waterloo
BIOL 110
Christine Dupont

Head and Neck DevelopmentIReviewacritical time for craniofacial development is wk 34 same as gastrulationbNeural crest cellsbones of faceanterior skullcMesodermposterior bonesbase of skulldLateral Plate Mesodermlaryngeal cartilageIISomitomeresaWeek 3 paraxial mesoderm differentiates into somitomeresidifferentiate in cranial to caudal fashionii7 somitomeresiiikey in segmenting brain into fore mid hind brain segments by inducing neural tube via chemogradientsbsomitomereincompletely differentiated in headcsomitecompletely differentiated found in lower bodyd somitomeres form all voluntary muscles in headneck but scaffold patterning is by connective tissue elementsIIINeural Crest Cells and Pharyngeal ArchesaNCCs migrate from neural folds in cranialtocaudal sequence to somitomeres pharyngeal arches brachial archesidirected by HOX genespopulate specific regions of headneckiiMSX2 genes specific suicide signal to NCCs along rhombomeres 351produces gaps brachial grooves2ensures nonmixing between populations of NCCsiiiRhombomere subdivision of hindbrain segment of neural tube1each rhombomere has its own HOX code2NCCs in each rhombomere migrate to brachial arches with compatible HOX codespecific link between facebrain developmentivNCCs provide link between development of facebrain key BUT also very sensitive to teratogensbPharyngeal Arches Brachial ArchesiGeneralth1develop during 4 week of gestation2lateral swellings on either side of head result from local proliferation of NCC 3give rise to specific cartilages and bones4pharyngeal groovesexternal delineations between brachial arches ectoderm covered5pharyngeal pouchesinternal deliniation between brachial arches endoderm lined6closing membranesectodermendoderm contact points ensuring nonmixing between brachial archesiiAortic Arch Arteries1
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