The Infrahyoid Muscles

Original Author: Oliver Jones
Last Updated: August 9, 2016
Revisions: 19

The infrahyoid muscles are a group of four muscles, located inferiorly to the hyoid bone in the neck. They can be divided into those in the superficial plane (sternohyoid and omohyoid), and those in the deep plane (sternothyroid and thyrohyoid).

Arterial supply to these muscles is via the superior and inferior thyroid arteries, with venous drainage via the corresponding veins.

This article will look at the anatomical course of these muscles, their actions and innervations.


Sternohyoid

Along with the omohyoid, the sternohyoid lies superficially in the neck.

Attachments: The sternohyoid muscle originates from the sternum and sternoclavicular joint. It ascends to insert onto the hyoid bone.

Actions: Depresses the hyoid bone.

Innervation: Anterior rami of C1-C3, carried by a branch of the ansa cervicalis.


Omohyoid

The muscle, like the suprahyoid digastric, is split into two bellies, connected by a muscular tendon. It is located slightly laterally to the sternohyoid.

Attachments: The inferior belly of the omohyoid arises from the scapula. It runs superiomedially, moving underneath the sternocleidomastoid. Here, it is attached to the superior belly by an intermediate tendon. This tendon is attached to the clavicle by the deep cervical fascia. The superior belly ascends to attach to the hyoid bone.

Actions: Depresses the hyoid bone.

Innervation: Anterior rami of C1-C3, carried by a branch of the ansa cervicalis.

Fig 1.0 - Lateral view of the neck musculature. Note the two bellies of the omohyoid muscle.

Fig 1.0 – Lateral view of the neck musculature. Note the two bellies of the omohyoid muscle.


Sternothyroid

This muscle is wider and deeper than the sternohyoid.

Attachments: The sternothyroid runs from the manubrium of the sternum to the thyroid cartilage.

Actions: Depresses the thyroid cartilage.

Innervation:  Anterior rami of C1-C3, carried by a branch of the ansa cervicalis.


Thyrohyoid

The thyrohyoid muscle is a short band of muscle, located underneath the posterior portions of the omohyoid and sternohyoid muscles. It is a continuation of the sternothyroid muscle.

Attachments: It arises from the thyroid cartilage of the larynx, and ascends to attach to the hyoid bone.

Actions: It depresses the hyoid. However, if the hyoid is fixed, it can raise the larynx.

Innervation: Anterior ramus of C1, carried within the hypoglossal nerve.

 

Fig 1.1 - Anterior view of the neck musculature. The right sternohyoid muscle has been removed to show the underlying muscles

Fig 1.1 – Anterior view of the neck musculature. The right sternohyoid muscle has been removed to show the underlying muscles

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Quiz

Question 1 / 4
Which of the infrahyoid muscles are found in the deep plane?

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Question 2 / 4
Which infrahyoid muscle is a continuation of the sternothyroid muscle?

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Question 3 / 4
Which of the following describes the innervation of thyrohyoid?

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Question 4 / 4
Which infrahyoid muscle depresses the thyroid cartilage?

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