Infrahyoid muscles

Diagram of the infrahyoid muscles

The infrahyoid muscles are a group of four muscles located in the anterior part of the neck, below the hyoid bone. These muscles are primarily responsible for the movement and stabilization of the hyoid bone and the larynx during swallowing and speech.

Anatomy

The infrahyoid muscles are composed of the following:

Sternohyoid

The sternohyoid muscle is a thin, narrow muscle that originates from the posterior surface of the manubrium of the sternum and the medial end of the clavicle. It inserts into the lower border of the hyoid bone. The sternohyoid muscle functions to depress the hyoid bone after it has been elevated during swallowing.

Omohyoid

The omohyoid muscle consists of two bellies, the superior and inferior, connected by an intermediate tendon. The inferior belly originates from the superior border of the scapula, and the superior belly inserts into the hyoid bone. The omohyoid muscle acts to depress and stabilize the hyoid bone.

Sternothyroid

The sternothyroid muscle is located beneath the sternohyoid muscle. It originates from the posterior surface of the manubrium and the first costal cartilage, and it inserts into the oblique line of the thyroid cartilage. The sternothyroid muscle functions to depress the larynx.

Thyrohyoid

The thyrohyoid muscle is a small muscle that originates from the oblique line of the thyroid cartilage and inserts into the lower border of the hyoid bone. It acts to depress the hyoid bone and elevate the larynx.

Function

The primary function of the infrahyoid muscles is to depress the hyoid bone and larynx during swallowing and speech. This action is crucial for the proper passage of food and air through the pharynx and into the esophagus and trachea, respectively. Additionally, these muscles help stabilize the hyoid bone, providing a firm base for the suprahyoid muscles to act upon during the elevation of the hyoid bone.

Innervation

The infrahyoid muscles are innervated by the ansa cervicalis, a loop of nerves derived from the cervical plexus, specifically from the anterior rami of the C1 to C3 spinal nerves. The thyrohyoid muscle, however, receives its innervation from fibers of the C1 nerve that travel with the hypoglossal nerve (cranial nerve XII).

Clinical Significance

Dysfunction of the infrahyoid muscles can lead to difficulties in swallowing (dysphagia) and speech. Conditions such as muscle weakness, nerve damage, or surgical trauma can impair the function of these muscles, affecting the movement of the hyoid bone and larynx.

Related Pages

• Hyoid bone
• Larynx
• Swallowing
• Ansa cervicalis
• Suprahyoid muscles