The myoblasts elongate, agregate and fuse to form multinucleated muscle fibers. The skeletal myoblasts are derived from the myotome regions of the somites, the branchial arches and the somatic mesoderm (body wall and limbs). During the 5th week the musculature of the body wall is divided into the dorsal (epimere) and ventral (hypomere) portion.

Limb musculature is derived from the somatic mesoderm which migrates into the limb buds. The condensations of the mesenchyme near the base of the buds are found in the 7th week of the development.
The spinal nerves penetrate into the limb mesenchyme and supply the extensor and flexor musculature.