Structural arrangement of the intrinsic muscles of the tongue and their relationships with the extrinsic muscles

The tongue is a dense muscular organ, in which the muscles are arranged in a confusing pattern. The intrinsic muscles were gross anatomically investigated in 25 cadavers to clarify their configuration. The superior longitudinal muscle (SLm) ran beneath the dorsal mucosa and was divided into bundles by the other muscles passing through it to the dorsum. The external bundle of the styloglossus, with the palatoglossus, coursed externally to the hyoglossus. Their fibers spread beneath the SLm or attached to the apex and the inferior longitudinal muscle (ILm) ascended from the root and joined them. The genioglossus and the anterior part of the hyoglossus extended internally and externally to the ILm, respectively, to the dorsum, and the vertical muscle was sandwiched between them. The transverse muscle passed laterally from the lingual septum. The fibers of the posterior part of the hyoglossus converged to the root and spread beneath the SLm. The intersections between these vertical and transverse fibers divided one another into bundles or lamellae. The middle bundle of the styloglossus, passing between the two parts of the hyoglossus, was divided into slips by the intersection with the genioglossus. The internal bundle of the styloglossus, with the glossopharyngeus, descended internally to the posterior part to the root. The findings indicate that the intrinsic and extrinsic muscles of the tongue are not independent groups, and their fibers form a three-dimensional latticework. Each muscle contains numerous bundles or lamellae as functional units that can act separately or cooperate across the muscles.