1. muscles fully contained (origin, belly, insertion) in the foot and toes. These muscles are arranged in four layers; all are innervated by the plantar branches of the tibial nerve. Although they may be capable of producing the actions described under their individual entries, as a group the primary function of the intrinsic muscles of the foot is to provide dynamic support of the longitudinal arch of the foot, resisting those forces that act momentarily to spread the arch during walking and running.
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