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
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).
|Styloglossus||Styloid process||Superolateral sides of the tongue||Hypoglossal|
|Hyoglossus||Hyoid bone||Lateral sides of the tongue||Hypoglossal|
|Genioglossus||Mental symphysis||Into tongue from tip to base||Hypoglossal|
|Palatoglossus||Palatine aponeurosis||Posterolateral sides of the tongue||Vagus|
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: