The sternothyroid muscle, or sternothyroideus, is an
infrahyoid muscle in the
neck. It acts to depress the
hyoid bone.
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 sternohyo ...
. It is shorter and wider than the sternohyoid.
Structure
The sternothyroid arises from the posterior surface of the
manubrium 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. Sha ...
, 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 ...
. 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.
Bran ...
.
Variations
Doubling; absence; accessory slips to the
thyrohyoid
The thyrohyoid muscle is a small skeletal muscle on the neck. It originates from the lamina of the thyroid cartilage, and inserts into the greater cornu of the hyoid bone. It is supplied by the hypoglossal nerve, and a branch of the ventral rami o ...
,
inferior pharyngeal constrictor
The inferior pharyngeal constrictor muscle is a skeletal muscle of the neck. It is the thickest of the three outer pharyngeal muscles. It arises from the sides of the cricoid cartilage and the thyroid cartilage. It is supplied by the vagus nerve ( ...
, 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 adip ...
.
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
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
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Muscles of the head and neck