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.