The sternothyroid muscle, or sternothyroideus, is an

infrahyoid muscle The infrahyoid muscles, or strap muscles, are a group of four pairs of muscles in the anterior (frontal) part of the neck. The four infrahyoid muscles are the sternohyoid, sternothyroid, thyrohyoid and omohyoid muscles. Excluding the sternothyro ...

in the

neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...

. It acts to depress the

hyoid bone The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical verteb ...

. It is below the

sternohyoid muscle The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum. It is one of the paired strap muscles of the infrahyoid muscles. It is supplied by the ansa cervicalis. It depresses the hyoid bone. Structure The sternoh ...

. It is shorter and wider than the sternohyoid.

Structure

The sternothyroid arises from the posterior surface of the

manubrium The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sh ...

of the

sternum The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. ...

, below the origin of the sternohyoid. It also arises from the edge of the cartilage of the first rib. It is inserted into the oblique line on the lamina of the

thyroid cartilage The thyroid cartilage is the largest of the nine cartilages that make up the ''laryngeal skeleton'', the cartilage structure in and around the trachea that contains the larynx. It does not completely encircle the larynx (only the cricoid cartilag ...

. It is in close contact with its fellow at the lower part of the neck, but diverges somewhat as it ascends. It is occasionally traversed by a transverse or oblique tendinous inscription.

Innervation

The sternothyroid muscle is innervated by the

ansa cervicalis The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid triangle. Its name means "handle of the neck" in Latin. Branc ...

Variations

Doubling; absence; accessory slips to the thyrohyoid, inferior pharyngeal constrictor, or to the

carotid sheath The carotid sheath is an anatomical term for the fibrous connective tissue that surrounds the vascular compartment of the neck. It is part of the deep cervical fascia of the neck, below the superficial cervical fascia meaning the subcutaneous adi ...

Function

The sternothyroid muscle depresses the hyoid bone, along with the other infrahyoid muscle.

Clinical significance

The upward extension of a thyroid swelling (

goitre A goitre, or goiter, is a swelling in the neck resulting from an enlarged thyroid gland. A goitre can be associated with a thyroid that is not functioning properly. Worldwide, over 90% of goitre cases are caused by iodine deficiency. The term is ...

) is prevented by the attachment of the sternothyroid to the thyroid cartilage. A goitre can therefore only grow to the front, back or middle but no higher.

Additional images

File:Gray507.png, Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries. File:Gray562.png, The fascia and middle thyroid veins. File:Gray794.png, Hypoglossal nerve, cervical plexus, and their branches. File:Gray957.png, Side view of the larynx, showing muscular attachments. File:Slide3c.JPG, Sternothyroid muscle

References

External links

* Photo of model at Waynesburg College
musclehead/sternothyroid
' * - "The Muscular triangle"
PTCentral
{{Authority control Muscles of the head and neck