Sternothyroid muscle

The sternothyroid muscle is an infrahyoid muscle of the neck that is innervated by the ansa cervicalis of the cervical plexus receiving fibers from the ventral rami of C1-C3 spinal nerves. The sternothyroid is a paired, flat strap of muscle that serves to fix the hyoid bone as well as depressing the larynx in phonation and in the terminal phase of swallowing.

Summary

• origin: posterior surface of manubrium sterni
• insertion: oblique line on the lamina of the thyroid cartilage
• innervation: anterior rami of C1-C3 spinal nerves through the ansa cervicalis
• action: depresses and fixes the hyoid bone

Gross anatomy

Origin

The sternothyroid muscles are paired broad, flat muscles that lie deep to the sternohyoid muscles. They originate from the lower part of the posterior surface of the manubrium so far inferiorly that there is no attachment to the clavicle or sternoclavicular joints.

Insertion

The muscle travels vertically upwards to attach to the oblique line on the lamina of the thyroid cartilage end-to-end with the thyrohyoid muscle.

Relations

The sternothyroid muscle is one of the infrahyoid “strap” muscles and is not easily visualized as it lies deep to the sternohyoid muscle. At its origin the sternothyroid muscle extends as far laterally as the first costal cartilage and as it ascends into the neck it covers the lateral lobe of the thyroid gland.

Blood supply

The sternothyroid muscles receive their blood supply from the superior thyroid arteries.

Innervation

The sternothyroid muscles are innervated by the anterior rami of C1-C3 (predominantly C2 and C3) through the ansa cervicalis of the cervical plexus.

Action

The sternothyroid muscles primarily depress and fix the hyoid bone and underlying larynx.