Histogenesis of Skeletal Musculature
At an early stage of development (in humans at about day 20), somites (Fig. A1) appear lateral to the neural groove (Fig. A2). The somite cells proliferate and some migrate to the notochord (Fig. B1), where they form the sclerotome (Fig. B2). Subsequently, a new cell layer, the myotome (Fig.C1), develops from the somite wall.