Morphological analyses of the human tongue musculature for three-dimensional modeling

Skilled movements of the tongue in speech articulation reflect complex formation of the tongue musculature, although its description in the anatomical literature is rather limited for developing a realistic computational model of the tongue. This study presents detailed descriptions of the muscular structure of the human tongue based on macroscopic and microscopic observations and provides three-dimensional schemata of the tongue musculature. Histologic examination revealed that the tongue consists of five strata, stacked along the courses of the fibers of the genioglossus muscle in proximal-distal directions. This stratum structure exists in the entire tongue tissue, indicating that the lingual musculature can be divided into the inner and outer regions. The former consisted of the "stem" and "core," and the latter of the "cover" and "fringe." In gross dissection, the tongue was cut into wedge-like blocks along the course of the genioglossus muscle to examine muscle fiber arrangement. Using this approach, it was determined that serial repetitions of "structural units" composed the inner musculature of the tongue. Each unit consisted of a pair of thin muscle fiber laminae; one was composed of the genioglossus and vertical muscles, and the other of the transverse muscle. In the apex, the laminae lacked the fibers of the genioglossus. These findings have been incorporated in three-dimensional schemata of the tongue musculature.