Morphological and histochemical studies of the genioglossus muscle.

The purpose of this preliminary study was to assess the histo-anatomic composition of the genioglossus muscle fibers. The genioglossus muscles were obtained from 4 cadavers and 1 autopsy specimen. On morphological study, the average diameters of the muscle fibers were seen to gradually increase, from the fibers that ran anteriorly to the dorsum of the tongue, to the fibers that ran posteriorly to the root of the tongue. Histochemical study revealed that type II fibers were significantly predominant in the anterior portion; there was no dominant fiber type in the posterior portion. Gradual changes in diameter were independent of fiber type. These findings may suggest that the fibers of the anterior portion are suitable for phasic action, and that the posterior is relatively tonic; and the posterior has larger absolute muscle strength than the anterior. It is thought that the fibers of the posterior portion might contribute to the maintenance of the mesopharyngeal airway and to vowel production, and that the anterior fibers might contribute to some fine movements and to consonant production.