Somite Development

Early stages in somite formation.

Presomitic paraxial mesoderm cells (pink) undergo mesenchymal-epithelial transition (MET), resulting in formation of epithelial somites (outer pink layer), organized around a mesenchymal core (violet). The outer epithelial cells undergo epithelial-mesenchymal transition (EMT) and differentiate to form the dermomyotome. Muscle progenitor cells migrate from the dermomyotome to form the myotome (gray). Muscle stem cells from the hypaxial dermomyotome region at the limb level migrate to form the limb musculature. The inner mesenchymal core differentiates to form the sclerotome.