Thyroarytenoid is a wide, paired muscle located between the thyroid and arytenoid cartilages of the larynx. It is one of the intrinsic muscles of larynx along with the oblique arytenoid, transverse arytenoid, posterior cricoarytenoid, lateral cricoarytenoid, cricothyroid, aryepiglotticus, thyroepiglottic muscles and vocalis.
Thyroarytenoid, cricothyroid and vocalis muscles work as a group to regulate the length and tension of the vocal folds. It is worth mentioning that some textbooks describe vocalis muscle as part of thyroarytenoid muscle.
|Origin||Angle of thyroid cartilage and adjacent cricothyroid ligament|
|Insertion||Anterolateral surface of arytenoid cartilage|
|Action||Draws arytenoid cartilages anteriorly, Relaxes vocal ligament (for low pitch sound)|
|Innervation||Inferior laryngeal nerve (of recurrent laryngeal nerve (CN X))|
|Blood supply||Laryngeal branches of superior and inferior thyroid arteries|
This article will discuss the anatomy and function of thyroarytenoid muscle.
Origin and insertion
Thyroarytenoid muscle arises from the inner surface of the inferior part of thyroid cartilage, near the midline, as well as cricothyroid ligament. Its fibers pass posterolaterally to insert into the anterolateral surface of the arytenoid cartilage.
Thyroarytenoid lies lateral to the conus elasticus, laryngeal ventricle and saccule. Some anatomists describe the superior portion of thyroarytenoid as a separate muscle called the vocalis muscle, the medial border of which is associated with the vocal ligament.
Some thyroarytenoid muscle fibers help to form the muscular layer of the vocal cords. While others support the wall of the ventricle and its appendix. Some muscle fibers extend into the aryepiglottic fold, with a few fibers continuing as far as the margin of the epiglottis, forming the thyroepiglotticus muscle.
Thyroarytenoid muscle is innervated by the recurrent laryngeal nerve, a branch of vagus nerve (CN X). It also receives a communicating branch from the external laryngeal nerve.
The thyroarytenoid muscle is supplied by the laryngeal branches of the superior and inferior thyroid arteries, It is drained by the internal jugular vein, via the superior and inferior laryngeal veins.
Due to its complex structure and multiple points of attachment, the thyroarytenoids aid in two distinct actions simultaneously; they draw the arytenoid cartilages anteriorly allowing the vocal ligaments to shorten, thicken and relax. Concurrently, they rotate the arytenoid cartilages medially which helps in closing the rima glottidis by bringing the two vocal cords together.
But what does that mean in real life? It means that the thyroarytenoids play a crucial part in controlling sound production or phonation, a process that requires a high-level of neuromuscular coordination. The vocal folds will not oscillate if they are not sufficiently close to one another, are not under sufficient tension or under too much tension.Learn more about the anatomy and function of the larynx and laryngeal muscles here.