The sternocleidohyoid muscle, also called the sternohyoid, is the most superficial of the muscles in the infrahyoid region and has a tapered shape approximately 20mm wide.
It receives that name, because it joins the hyoid and the sternum. It belongs to the muscles of the anterior neck group, specifically the infrahyoid muscles.
This region is made up of four muscles, located in the lower part of the hyoid bone, two of which are located in the superficial plane: sternohyoid and omohyoid muscles; and two in the deep plane: sternothyroid and thyrohyoid muscles.
These four muscles together are responsible for lowering the hyoid bone, allowing swallowing as the esophagus widens.
Both sternocleidohyoid muscles together with both thyrohyoid muscles form a very important rhomboid-shaped space called the “tracheostomy rhombus”.
This rhombus is delimited by both medial borders of the thyrohyoid muscles below, and both medial borders of the sternocleidohyoid muscles above. It is important, as it delimits the space where the tracheal rings can be accessed more easily.
An anatomical characteristic of the infrahyoid muscles is that if a horizontal cut is made at any height of the neck, the four muscles will never be appreciated simultaneously.
This is because the thyrohyoid and sternothyroid muscles (both deep infrahyoid muscles) are not in the same plane, one is higher than the other.
Origin and insertion
The sternocleidohyoid muscle is located mostly in the infrahyoid region, however, its lower extremity lies behind the sternocleidomastoid muscle and the sternoclavicular joint.
It originates in the medial quarter of the clavicle, in the posterior aspect of the sternoclavicular ligament, in the lateral half of the sternal manubrium, and in the first costal cartilage.
From there, it travels upward and toward the center to attach to the lower edge of the hyoid bone.
Relations
The sternocleidohyoid muscle is contained within the pretracheal sheet of the cervical fascia.
It is covered in the lower part by the sternocleidomastoid muscle, being more superficial in the upper part. Its lateral border is reached by the omohyoid muscle.
Its medial border, separated from its counterpart on the opposite side at its lower end and approaching as both go up in its course, forms the "tracheostomy rhombus".
Along the path of the muscle it lightly covers the sternothyroid muscle and the thyrohyoid muscle.
Its deep face covers muscles of the deep plane, corresponding from bottom to top, to the thyroid gland, the trachea and the larynx
Irrigation
The arterial supply to the infrahyoid muscles is made through the superior and inferior thyroid arteries, collateral branches of the external carotid artery, with venous drainage through the homonymous veins.
Innervation
All the infrahyoid muscles are innervated by the hypoglossal loop, by an anastomosis that occurs between a branch that descends from the hypoglossus and a branch of the deep cervical plexus.
It is called the hypoglossal loop and sends fibers that innervate all the infrahyoid muscles with the exception of the thyrohyoid muscle.
The muscle is innervated in the form of branches from the cervical loop of the hypoglossus. Anterior branches of C1-C3.
Features
Depending on the location of the sternohyoid muscle, several important functions can be attributed:
- In swallowing
- Phonation
- In the movement of the head
- In the movement of the neck
However, the main function is the depression of the hyoid bone.
This bone is located under the lower jaw; It has a “U” shape and is partially responsible for the movement of the tongue and the action of swallowing.
This last function is performed by being depressed (decreased through contractions) by the sternohyoid muscle.
Dystonia of the hyoid muscles
The dystonia of the muscles present in the infrahyoid region is generally a focal dystonia, characterized by a triad of speech change, stiff neck and dysphagia.
The patients who present this triad are those whose professions make use of the vocal muscles: teachers and musicians or singers.
References
- Anatomy, Head and Neck, Muscles._ Suprahyoid Muscles of the Neck._ Recovered from earthslab.com.
- Drake RL, Vogl A., Mitchell, AWM GRAY. Anatomy for students + Student Consult. 2011. Elsevier. Madrid. P. 954 - 959
- Healthline (2015)._ Sternohioid._ Recovered from healthline.com
- US National Library of Medicine National Institutes of Health._ Hyoid muscle dystonia: A distinct focal dystonia syndrome._ Retrieved from ncbi.nlm.nih.gov
- _ The Infrahyoid muscles._ Recovered from teachmeanatomy.info.