A histochemical study of lingual muscle fibers in rat.

Twelve male 9-week-old Wistar rats were used in this study. Intrinsic (transverse, longitudinal and vertical) and extrinsic (genioglossus) muscles of the tongue were examined using histochemical methods. Intrinsic muscle consists mainly of intermediate and red fiber types; in contrast, there is an increase in the white fiber type in extrinsic muscle. The predominant fiber types, red and intermediate, in the intrinsic muscle are smaller than those of the extrinsic muscle. Among the intrinsic muscles, the longitudinal muscle fibers show a tendency to be smaller in size than the others. The continuous movement of the intrinsic muscle fibers influences the shape of the tongue and contributes to versatile activity in chewing. In contrast, extrinsic muscle of the rat tongue reflects powerful movements in mastication, swallowing and squeaking owing to the increased percentage composition of the white fiber type.