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 vertebr ...
.
It is below the
sternohyoid muscle. 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. Sha ...
of the
sternum, below the origin of the sternohyoid. It also arises from the edge of the cartilage of the
first rib
The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels.
The sternum, together known as the thoracic cage, is a semi-r ...
. 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 cartilage ...
. 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 adipo ...
.
Function
The sternothyroid muscle depresses the hyoid bone, along with the other infrahyoid muscle.
Clinical significance
The upward extension of a thyroid swelling (
goitre) 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
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Muscles of the head and neck