The thick fan-shaped genioglossus muscles make a substantial contribution to the structure of the tongue. They occur on either side of the midline septum that separates left and right halves of the tongue.
The genioglossus muscles originate from the superior mental spines on the posterior surface of the mandibular symphysis immediately superior to the origin of the geniohyoid muscles from the inferior mental spines (Fig. 8.256). From this small site of origin, each muscle expands posteriorly and superiorly. The most inferior fibers attach to the hyoid bone. The remaining fibers spread out superiorly to blend with the intrinsic muscles along virtually the entire length of the tongue.
The genioglossus muscles: depress the central part of the tongue, and protrude the anterior part of the tongue out of the oral fissure (i.e., stick the tongue out).
Like most muscles of the tongue, the genioglossus muscles are innervated by the hypoglossal nerves [XII].
Asking a patient to “stick your tongue out” can be used as a test for the hypoglossal nerves [XII]. If the nerves are functioning normally, the tongue should protrude evenly in the midline. If the nerve on one side is not fully functional, the tip of the tongue will point to that side.
The hyoglossus muscles are thin quadrangular muscles lateral to the genioglossus muscles (Fig. 8.257).
Each hyoglossus muscle originates from the entire length of the greater horn and the adjacent part of the body of the hyoid bone. At its origin from the hyoid bone, the hyoglossus muscle is lateral to the attachment of the middle constrictor muscle of the pharynx. The muscle passes superiorly and anteriorly through the gap (oropharyngeal triangle) between the superior constrictor, middle constrictor, and mylohyoid to insert into the tongue lateral to the genioglossus and medial to the styloglossus.
The hyoglossus muscle depresses the tongue and is innervated by the hypoglossal nerve [XII].
An important landmark. The hyoglossus muscle is an important landmark in the floor of the oral cavity:
The lingual artery from the external carotid artery in the neck enters the tongue deep to the hyoglossus, between the hyoglossus and genioglossus.
The hypoglossal nerve [XII] and lingual nerve (branch of the mandibular nerve [V3]), from the neck and infratemporal fossa of the head, respectively, enter the tongue on the external surface of the hyoglossus.
The styloglossus muscles originate from the anterior surface of the styloid processes of the temporal bones. From here, each muscle passes inferiorly and medially through the gap (oropharyngeal triangle) between the middle constrictor, superior constrictor, and mylohyoid muscles to enter the lateral surface of the tongue where they blend with the superior margin of the hyoglossus and with the intrinsic muscles (Fig. 8.258).
The styloglossus muscles retract the tongue and pull the back of the tongue superiorly. They are innervated by the hypoglossal nerves [XII].
The palatoglossus muscles are muscles of the soft palate and the tongue. Each originates from the undersurface of the palatine aponeurosis and passes anteroinferiorly to the lateral side of the tongue (Fig. 8.259).
The palatoglossus muscles: elevate the back of the tongue, move the palatoglossal arches of mucosa toward the midline, and depress the soft palate.
These movements facilitate closing of the oropharyngeal isthmus and as a result separate the oral cavity from the oropharynx.
Unlike other muscles of the tongue, but similar to most other muscles of the soft palate, the palatoglossus muscles are innervated by the vagus nerves [X].
The major artery of the tongue is the lingual artery (Fig. 8.260).