Muscle Classification
The styloglossus muscle belongs to the group of extrinsic skeletal muscles of the tongue. The intrinsic muscles are arranged in three mutually perpendicular planes and alter the shape of the tongue, whereas the extrinsic muscles originate from bone and insert into the tongue, altering its position.
Along with the m. styloglossus, the extrinsic muscles of the tongue include:
- Genioglossus muscle (m. genioglossus) — lies directly beneath the mucosa of the oral floor, fans out into the tongue, and protrudes the tongue forward and downward.
- Hyoglossus muscle (m. hyoglossus) — draws the tongue backward and downward.
- Palatoglossus muscle (m. palatoglossus) — constricts the fauces (isthmus of the pharynx).
Function
The m. styloglossus draws the tongue backward and upward.
Topography and Relations
- Styloid diaphragm — a septum formed by the muscles arising from the styloid process (m. styloglossus, m. stylopharyngeus, m. stylohyoideus) and their fascial sheaths. It divides the parapharyngeal space (spatium parapharyngeum) along the lateral wall of the pharynx into two compartments:
- Anterior parapharyngeal space — filled with adipose tissue, contains ascending pharyngeal vessels and the pharyngeal process of the parotid gland.
- Posterior (retrodiahragmatic) space — contains the internal carotid artery, internal jugular vein, and four pairs of cranial nerves (CN IX, X, XI, XII).
- Relation to vessels — The m. styloglossus, together with the m. stylopharyngeus, separates the cervical portion of the internal carotid artery from the parotid gland. The artery runs along the lateral wall of the pharynx, medial to the parotid gland.
- Palatal region — The m. styloglossus is listed among the major structures depicted in topographical views of the hard and soft palate (inferior view).
Blood Supply and Innervation
Key neurovascular relationships include:
- Innervation of tongue muscles — predominantly by the hypoglossus nerve (n. hypoglossus, CN XII).
- Blood supply to the tongue — via the a. lingualis.
- Venous drainage — via the v. lingualis, which drains into the internal jugular vein (v. jugularis interna).
- Lymphatic drainage — to the submental, submandibular, and deep cervical lymph nodes (nodi lymphoidei submentales, submandibulares, cervicales profundi).
Nerve supply to various regions of the tongue includes: anterior 2/3 — n. lingualis and chorda tympani (CN VII); posterior 1/3 — glossopharyngeal nerve (n. glossopharyngeus, CN IX) and superior laryngeal nerve (n. laryngeus superior).