Abstract
Perineal muscles originate from the hindlimb musculature and deploy novel developmental mechanism ’In-Out’. Medial margin of the scapula is of somitic origin not only in birds but also in mammals.
Cucullaris/trapezius-sternocleidomastoideus muscle develops from lateral plate mesoderm and its developmental programme corresponds to that of the head musculature. ’In-Out’ mechanism is deployed also during the development of the forelimb. During the ‘Out‘ phase only the myogenic cells translocate, not the connective tissue, which remains locally.
Tbx5 gene controls the development of the sternum, which developmentally belongs to the forelimb programme. New developmental classification of the pectoral girdle muscles (deep and superficial).
Diaphragmatic musculature is linked to the development of the forelimb.