Transverse arytenoid muscle

Origin and insertion

Transverse arytenoid muscle is a single flat band of muscle stretching between the arytenoid cartilages of the larynx. It attaches to the posterior aspect of the muscular process and adjacent lateral border of the arytenoid cartilages. The muscle fibers run horizontally to insert into the same location on the opposite arytenoid cartilage. 

If you are finding these and other muscle attachments a bit tricky, why not take a look at our muscle anatomy reference chart, where you can find all the attachment sites, innervation and function of muscles compiled into one neat list!

Relations

The transverse arytenoid muscle is the only unpaired intrinsic muscle of the larynx. It is located at the posterior aspect of the larynx, just superior to the cricoid cartilage. It closes the gap between the arytenoid cartilages and fills the concavities on their posterior surface. Superficial to the transverse arytenoid muscle you will find the two oblique arytenoid muscles. Sometimes the transverse and oblique arytenoids are considered to be two parts of the same muscle; when taken together these 3 muscles are known simply as the arytenoid, or interarytenoid, muscle.

Sitting externally to the transverse arytenoid and other intrinsic muscles of the larynx are found the circular (constrictor) and longitudinal muscles of the pharynx. Together these muscles form a semicircular tube around the pharynx and larynx.

Innervation

Innervation to transverse arytenoid comes from the recurrent laryngeal nerves, which are branches of the vagus nerves (CN X). The recurrent laryngeal nerves innervate all the muscles of the larynx, except for the cricothyroid muscles. 

The transverse arytenoid muscle also receives branches from the internal branches of the superior laryngeal nerve, another branch of the vagus nerve. However there is debate about whether these nerves provide any motor innervation, as the internal branch is considered to only contain sensory fibres.

Blood supply

Transverse arytenoid is supplied by the laryngeal branches of the superior and inferior thyroid arteries.

Functions

This muscle has two main functions; adducting the vocal cords and closing the rima glottidis. 

By attaching to both arytenoid cartilages, contraction of transverse arytenoid’s horizontal muscle fibers pulls the arytenoid cartilages closer together (adduction), consequentially adducting the vocal folds. In doing so, this muscle also closes the posterior aspect of the rima glottidis and narrows the laryngeal inlet. 

Combined action of the transverse arytenoid, lateral cricoarytenoid, oblique arytenoid and aryepiglottic muscles closes the rima glottidis fully. This is a reflex action, which occurs in response to the presence of liquids or particles in the laryngeal vestibule approaching the rima glottidis. Thus preventing the inhalation of food or liquid.

Adduction of the arytenoid cartilages is also important in phonation, or sound production. When the vocal cords are brought close together, the rima glottidis is closed. That allows pressure to build up in the lower respiratory tract. Expiration of air forces the rima glottidis to open slightly, causing vibrations in the vocal cords and resulting in production of sound.