Orofacial Anatomy

Health professionals practicing myofunctional therapy must possess adequate knowledge of the orofacial and cervical musculature, including associated bony attachments and innervations (Figure 2). Myofunctional therapy exercises may target any combination of the muscles of mastication, muscles of facial expression, or muscles used during normal tongue movements and swallowing. In addition, if a forward head posture has been noted, therapy may target cervical muscles. Muscles of particular interest to the myofunctional therapist are: the buccinator, which is used in chewing and facial expression; the orbicularis oris, which controls movements of the mouth and lips, and the muscles of the tongue, which are involved in taste, speech, mastication, and deglutition.6,7

Figure 2. Important facial musculature.8

Diagram showing important facial musculature.
Courtesy of: Gianni Bistoni.

The tongue is a unique and complex network of muscle fibers divided into two types: extrinsic and intrinsic. There are 4 extrinsic muscles (Figure 3) and 4 intrinsic muscles. The extrinsic muscles have fixed origins outside of the tongue, while the intrinsic muscles have origins and insertions completely within the tongue. Of the four extrinsic muscles, only the palatoglossus muscle is not innervated by the hypoglossal (XII) nerve; it is innervated by the vagus (X) nerve (Table 1).

Figure 3. Extrinsic muscles of the tongue.9

Diagram showing extrinsic muscles of the tongue.

Table 1. Extrinsic muscles of the tongue: origin, insertion, innervation, and function.10,11

StyloglossusStyloid processSuperolateral sides of the tongueHypoglossal
retracts, elevates
HyoglossusHyoid boneLateral sides of the tongueHypoglossal
depresses, retraction
GenioglossusMental symphysisInto tongue from tip to baseHypoglossal
protrudes, depresses
PalatoglossusPalatine aponeurosisPosterolateral sides of the tongueVagus
elevates, retracts

The four intrinsic muscles are named for their locations and the direction of their fibers (Figure 4).10 All intrinsic tongue muscles are innervated by the Hypoglossal nerve. The four intrinsic muscles are:

  • Superior longitudinal muscle: located closest to the dorsal surface of the tongue, and fibers travel lengthwise from base to tip.
  • Inferior longitudinal muscle: located at the sides of the tongue, and fibers travel lengthwise from base to tip.
  • Vertical muscle: located in the middle of the tongue body, and fibers travel from the superior longitudinal muscle to the inferior longitudinal muscle.
  • Transverse muscle: located in the middle of the tongue body, and fibers travel from the septum to the lateral mucous membranes of the tongue.

Figure 4. Intrinsic muscles of the tongue.12

Diagram showing intrinsic muscles of the tongue.