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Figure 8. A model of the intrinsic structure of the tongue based on Takemoto (2001). Layer 1 is the mucous membrane (gustatory on the upper surface) ensheathing the tongue. Layer 2, which also invests the body of the tongue, includes the important superior longitudinal (SL) muscles. Fibers from the genioglossus and verticalis interweave with the SL fibers. Layer 3 is the body of the tongue. It consists of the interleaved laminae of the transversus (T) and verticalis (V), with contributions from the genioglossus (GG). Layer 4 shows fibers of GG medially, with the fibers of the inferior longitudinalis evident laterally. Layer 5 shows the ‘genioglossus’ layer. This midline paired muscle plays a major role in determining global tongue position and tongue surface shape. Reproduced with permission from Professor Takemoto and the Journal of Speech, Language and Hearing Research.
