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Fig. 2. Tongue anatomy: classical definitions. (A) Shown here are the intrinsic
muscles – that is, the longitudinalis (superior and inferior),
transversus and verticalis muscles – in a coronal cross-section of the
mammalian tongue. By definition, the intrinsic muscles have no bony
attachments, being wholly contained within the tongue. (B) As conventionally
defined, the extrinsic muscles insert into the tongue from a superior
direction (palatoglossus), postero-superior direction (styloglossus),
postero-inferior direction (hyoglossus) and antero-inferior direction
(genioglossus). The genioglossus is a large muscle comprising the bulk of the
posterior tongue, which originates at the mental spine of the mandible and
enters the tongue from below. As noted in the text, while the extrinsic
muscles are distinct in their anatomy and physiology at the points of bony
attachment, they merge with the intrinsic fibers at the point of insertion
into the tongue proper.