The Suprahyoid Muscles

Original Author: Oliver Jones
Last Updated: January 12, 2017
Revisions: 22

The suprahyoid muscles are a group of four muscles, located superiorly to the hyoid bone of the neck. They all act to elevate the hyoid bone; an action involved in swallowing.

Arterial supply to these muscles is via branches of the facial, occipital and lingual arteries.

In this article, we shall look at the anatomy of the suprahyoid muscles – their attachments, actions and innervation.


Stylohyoid

The stylohyoid is a thin muscular strip, which is located superiorly to the digastric muscle.

  • Attachments: Arises from the styloid process of the temporal bone, and attaches to the lateral side of the hyoid bone.
  • Actions: Initiates a swallowing actions by pulling the hyoid bone in a posterior and superior direction.
  • Innervation: Mandibular branch of the facial nerve (CN VII).
Fig 1.0 - Lateral view of the neck, showing the stylohyoid and digastric muscles.

Fig 1.0 – Lateral view of the neck, showing the stylohyoid and digastric muscles.


Digastric

This muscle is comprised of two muscular bellies, connected by a tendon. In some cadavers this tendon can perforate the stylohyoid.

  • Attachments:  The anterior belly arises from the digastric fossa of the mandible. The posterior belly arises from the mastoid process of the temporal bone. The two bellies are connected by an intermediate tendon, which is attached to the hyoid bone via a fibrous sling.
  • Actions: Depresses the mandible and elevates the hyoid bone.
  • Innervation: The two parts of the digastric muscle have different innervations. The anterior belly is innervated by the inferior alveolar nerve, a branch of the mandibular nerve (which is derived from the trigeminal nerve, CN V). The posterior belly is innervated by the digastric branch of the facial nerve.

Mylohyoid

The mylohyoid muscle is a broad, triangular shaped muscle. It forms the floor of the oral cavity, thus supporting the floor of the mouth.

  • Attachments: It originates from the mylohyoid line of the mandible, and attaches onto the hyoid bone.
  • Actions: Elevates the floor of the mouth and the hyoid bone.
  • Innervation: Inferior alveolar nerve, a branch of the mandibular nerve (which is derived from the trigeminal nerve).
Fig 1.1 - The suprahyoid muscles of the neck.

Fig 1.1 – The suprahyoid muscles of the neck.


Geniohyoid

Located deep to the mylohyoid muscle, the geniohyoid lies close to the midline of the neck.

  • Attachments: Arises from the inferior mental spine of the mandible. It then travels inferiorly and posteriorly to attach to the hyoid bone.
  • Actions: Depresses the mandible and elevates the hyoid bone.
  • Innervation: C1 nerve roots that run within hypoglossal nerve.

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Question 1 / 4
What is the main action of the suprahyoid muscles?

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Question 2 / 4
Which of the suprahyoid muscles is comprised of two muscular bellies, connected by a tendon?

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Question 3 / 4
Which cranial nerve innervates the mylohyoid muscle?

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Question 4 / 4
Which suprahyoid muscle lies closest to the midline of the neck?

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