Craniofacial Muscles

14 Tongue Muscle Response to Neuromuscular Diseases and Speci fi c Pathologies
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Fig. 14.5 Deformational pattern of the tongue base during respiration. BWA and BWP base
anterior (#1–#2) and posterior (#3–#4) widths; BL base length (#1–#3); BT base thickness (#1–#5);
GG genioglossus; SG styloglossus; TH thyrohyoid; MC middle pharyngeal constrictor; V/T transversus/verticalis;
SL superior longitudinalis; Flow, Pres. and Vol . respiratory fl ow, pressure, and
volume. Two dash lines de fi ne the phase of inspiration (ins.), and red arrows indicate tongue base
deformation during the inspiration phase. Refer to n for the locations of crystal pairs
phase, the tongue base becomes thinner, narrower, and longer, and the genioglossus
muscle is the most active. During the expiration phase, rhythmic activity bursts of
tongue muscles disappear except for sporadic activation of the styloglossus (Fig. 14.5 )
(Herring et al . 2011 ) .
14.2.3 Spatio-Temporal Coupling in Volumetric
and Dimensional Changes
According to the muscular hydrostat theory of tongue motor control, the constant
volume of the tongue is achieved by its deforming or displacing in various regions
and dimensions via contractions of highly de fi ned intrinsic and extrinsic tongue
muscles (Kier and Smith 1985 ) . Although the entire tongue is incompressible, a
volumetric change deriving from independent motor control of regions may occur
to allow its diverse functions to be accomplished (Slaughter et al . 2005 ; Hiiemae
and Palmer 2003 ) , as the tongue motor control is far beyond the whole muscle level
(Odeh et al . 1995 ) . Therefore, the changes in distance (elongation or shortening) in