Skeletal muscles of the appendicular skeleton (126 bones in the human) that move the appendages or distal parts of the body (fins, limbs, wings). Muscles in general are classified as either extrinsic or intrinsic. Extrinsic (or axial) muscles have their origins on the axial skeleton or fasciae of the trunk (part that is stationary) and insertions (part that moves) on the girdles or bones in the limbs. The intrinsic (or appendicular) muscles have origins on the girdles or proximal skeleton and insertions on the more distal parts. During development, myotomes, behind the head and pharynx, form the appendicular muscles. Like the appendicular muscles, the growth of the appendicular skeleton is poorly understood, but is probably initiated by localised secretion of the fibroblast growth factor-8 from an unknown origin. Retinoic acid also acts locally in this process, as it is known that there is failure of limb growth when it is inhibited.
See Axial muscles, Fibroblast growth factor (FGF), Muscle fiber, Musculoskeletal system, Myotome, Pharynx, Retinoic acid (RA), Striated (or striped or voluntary) muscle