Thyrohyoid muscle

The thyrohyoid muscle is a small quadrilateral strap (infrahyoid) muscle of the anterior neck.

Anatomical details

1. Origin

Oblique line on the lamina of the thyroid cartilage.

2. Insertion

Fibres ascend from the oblique line and insert into the inferior border of the body and greater horn of the hyoid bone. It is sometimes considered as an upward continuation of the sternothyroid muscle.

Innervation

C1 fibres carried via the hypoglossal nerve (cranial nerve XII).

• Note: The first cervical spinal nerve (C1) sends motor fibres that briefly travel with the hypoglossal nerve (cranial nerve XII) — a “hitchhiking” pathway that allows them to reach their target muscles. These fibres do not supply the tongue but branch off from it to innervate the thyrohyoid and the geniohyoid muscles. The hypoglossal nerve simply as a conduit. Clinically, a C1 lesion affects both these muscles, while a hypoglossal nerve lesion distal to where the C1 branches off from the hypoglossal, affects tongue movement only.

Blood supply

Superior thyroid and lingual arteries, which are branches of the external carotid artery.

Action

The thyrohyoid muscle depresses the hyoid bone. However, when the hyoid is fixed, it elevates the larynx (important during swallowing).

Relations

The thyrohyoid muscle lies deep to the omohyoid and sternohyoid muscles. It forms the upper continuation of the sternothyroid muscle.