The sternothyroid muscle (or sternothyroideus) is an infrahyoid muscle of the

neck The neck is the part of the body in many vertebrates that connects the head to the torso. It supports the weight of the head and protects the nerves that transmit sensory and motor information between the brain and the rest of the body. Addition ...

. 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 verte ...

Structure

The two muscles are in contact with each other proximally (close to their origin), but diverge distally (towards their insertions).

Origin

The sternothyroid arises from the posterior surface of the

manubrium The sternum (: sternums or sterna) 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, human lung, lungs, and ma ...

of the

sternum The sternum (: sternums or sterna) 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 bl ...

from the midline to the notch for the first rib (inferior to the origin of the sternohyoid muscle), and the posterior margin of the first

costal cartilage Costal cartilage, also known as rib cartilage, are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the thorax. Costal cartilage is only found at the anterior ends of the ribs, pr ...

Insertion

It inserts onto the oblique line of the lamina of thyroid cartilage.

Innervation

The sternothyroid muscle receives motor innervation from branches of the

ansa cervicalis The ansa cervicalis (or ansa hypoglossi in older literature) is a loop formed by muscular branches of the cervical plexus formed by branches of cervical spinal nerves C1-C3. The ansa cervicalis has two roots - a superior root (formed by branch o ...

(ultimately derived from cervical spinal nerves C1-C3).

Relations

The sternothyroid muscle is shorter and wider than the sternohyoid muscle and is situated deep to and partially medial to it.

Variations

The muscle may be absent or doubled. It may issue accessory slips to the

thyrohyoid muscle The thyrohyoid muscle is a small skeletal muscle of the neck. Above, it attaches onto the greater cornu of the hyoid bone; below, it attaches onto the oblique line of the thyroid cartilage. It is innervated by fibres derived from the cervical spin ...

, inferior pharyngeal constrictor muscle, or the

carotid sheath The carotid sheath is a condensation of the deep cervical fascia enveloping multiple vital neurovascular structures of the neck, including the common and internal carotid arteries, the internal jugular vein, the vagus nerve (CN X), and ansa c ...

Actions/movements

The sternothyroid muscle indirectly depresses the hyoid bone by means of pulling the thyroid. When the hyoid bone is fixed, it instead elevates the larynx (producing an increased voice pitch).

Clinical significance

The upward extension of a thyroid swelling (

goitre A goitre (British English), or goiter (American English), 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 ...

) 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 The inferior carotid triangle (or muscular triangle), is bounded, in front, by the median line of the neck from the hyoid bone to the sternum; behind, by the anterior margin of the sternocleidomastoid; above, by the superior belly of the omohyoid. ...

"
PTCentral
{{Authority control Muscles of the head and neck