Stylohyoid muscle

Origin and insertion

Stylohyoid is a small, thin muscle that arises from the posterior surface of the styloid process of temporal bone. The point of origin is very close to the base of the styloid process. The muscle travels anteroinferiorly and medially, attaching to the body of hyoid bone, right at its intersection with the greater horn of hyoid bone.

Relations

The stylohyoid muscle is extremely variable. In certain individuals it can be absent, while in others it can be doubled. When present, the muscle is located superior to the hyoid bone in the anterior triangle of the neck. It forms the superior border of the carotid triangle together with the posterior belly of the digastric muscle. Along its path, stylohyoid runs alongside and just superior to the posterior belly of the digastric muscle. Close to its insertion point, the muscle is briefly split into two slips by the intermediate tendon of digastric muscle which passes through the belly of stylohyoid muscle. The two slips reunite before reaching the insertion point, which is located superiorly to the attachment of the superior belly of omohyoid muscle.

Throughout its course, stylohyoid has several important relations:

• Medial (deep) - internal carotid artery, accessory nerve (CN XI) and hypoglossal nerve (CN XII).
• Inferior - lingual artery (second part), facial artery.
• Superficial (lateral) - external carotid artery, facial vein and facial nerve  (CN VII).
• Posteroinferiorly - submandibular salivary gland.

Innervation

Stylohyoid receives innervation from the stylohyoid branch of the facial nerve (Cranial nerve 7). The branch arises right after the facial nerve passes the mastoid process of temporal bone to enter the middle part of the muscle.

Blood supply

The stylohyoid muscle receives arterial blood from branches of the facial, occipital and posterior auricular arteries. The external carotid artery also gives off the posterior auricular artery just superior to it. The internal jugular vein is responsible for draining venous blood from the stylohyoid muscle.

Functions

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Contraction of the stylohyoid muscle results in elevation and retraction (posterior movement) of the hyoid bone. This action also results in tongue retraction and lengthening the floor of the mouth. Tongue retraction is important during swallowing (deglutition) because it pushes the food bolus back towards the soft palate. In addition, the stylohyoid helps to keep the pharynx open during inspiration by tensing the floor of the mouth.

For more information about the suprahyoid muscles and other muscles of the ventral neck, take a look below: