Thyrohyoid muscle

At a glance

English

Thyrohyoid muscle

Latin (TA2)

Musculus thyreohyoideus

System

Muscle

Region

Neck

Side

Paired, left and right

About the thyrohyoid muscle

Thyrohyoid is the shortest of the infrahyoid muscles and lies in the carotid triangle of the neck. It is roughly quadrilateral and looks like an upward continuation of sternothyroid, since it starts from the same ridge on the larynx where sternothyroid ends. Sternohyoid and the superior belly of omohyoid cover it in front.

Its lower attachment is the oblique line on the outer face of the thyroid cartilage lamina. From there it rises to the underside of the hyoid's greater horn and the adjacent body. Between it and the thyrohyoid membrane runs the internal laryngeal nerve with the superior laryngeal artery, which pierce the membrane to enter the larynx.

The muscle works in two directions. When the larynx is fixed, it pulls the hyoid down. When the hyoid is fixed by the suprahyoid muscles, it lifts the larynx towards the hyoid, as happens during swallowing and when the voice rises. By altering where the larynx sits and how it is shaped, it helps in producing sound.

Thyrohyoid stands apart from the rest of its group because its nerve does not come from the ansa cervicalis. Instead it receives a branch of fibres from C1 that travel for a short way with the hypoglossal nerve before leaving it. The same arrangement is found in many other mammals, including the horse.

Attachments, action and supply

Origin

Oblique line of the thyroid cartilage, on the outer face of its lamina.

Insertion

Underside of the greater horn and adjoining body of the hyoid bone.

Action

Depresses the hyoid when the larynx is fixed; raises the larynx towards the hyoid when the hyoid is fixed.

Nerve supply

Fibres of C1 carried by the hypoglossal nerve (nerve to thyrohyoid).

Blood supply

Infrahyoid branch of the superior thyroid artery.