Fig. 13. Role of muscular synergy in the generation of lingual deformation. Conceptual drawing depicting the way in which synergistic contractions involving the intrinsic and extrinsic muscles may contribute to prototypical deformations, namely anterior protrusion, bolus accommodation during swallowing and bolus propulsion during swallowing. In each instance, muscle action is viewed from the sagittal, anterior coronal and posterior coronal perspectives. In the case of anterior protrusion, a principal role is played by the simultaneous contractions of the transversus and verticalis muscles, with a secondary role played by the genioglossus (at least in the human). In the case of bolus accommodation during swallowing, a principal role is played by the midline genioglossus fibers, with a secondary role played by the longitudinalis, verticalis and tranversus fibers, which serve to stiffen, broaden and bend the accommodating concavity. In the case of bolus propulsion, a synergistic role is played by the genioglossus, hyoglossus and styloglossus merging with the inferior longitudinalis, as well as the stiffening effect of bidirectional contraction of the core lingual fibers.