Posterior cricoarytenoid muscle

Origin and insertion

The posterior cricoarytenoid muscle originates from the posterior surface of the lamina of the cricoid cartilage. From this broad attachment the muscle fibers converge towards a narrower insertion onto the superoposterior surface of the muscular process of the arytenoid cartilage. In doing so, the superior fibers travel horizontally, the middle fibers pass obliquely and the inferior fibers must take a more vertical path.

Relations

Posterior cricoarytenoid muscle covers the majority of the posterior surface of cricoid cartilage. It is located inferior to the oblique and transverse arytenoid muscles and posterior to its insertion-sharing antagonist, the lateral cricoarytenoid muscle. The branches of the recurrent laryngeal nerve run on the posterior side of the posterior cricoarytenoid muscle.

Innervation

Like the majority of the intrinsic muscles of the larynx, the posterior cricoarytenoid is innervated by the inferior laryngeal nerve. The inferior laryngeal nerve is the terminal branch of the recurrent laryngeal nerve which carries information from the vagus nerve (CN X).

Blood supply

Posterior cricoarytenoid muscle is supplied by the laryngeal branches of the superior and inferior thyroid arteries. These are branches of the external carotid and subclavian arteries respectively.

The venous blood is first drained into the superior and inferior laryngeal veins which then empties into the internal jugular vein.

Function

Posterior cricoarytenoid muscle is the only muscle of the larynx that abducts the vocal cords and therefore opens the rima glottidis. It is an antagonist muscle to the lateral cricoarytenoid muscle which acts to protect the airway by closing the glottis.

Contraction of the posterior cricoarytenoid muscle rotates the arytenoid cartilages laterally and pulls them posterolaterally. This separates the vocal cords and assists the other intrinsic muscles in lengthening the vocal cords, therefore allowing the passage of air during inspiration and expiration. This action makes the posterior cricoarytenoid muscle the most important muscle in the larynx in the act of respiration. Owing to the fact that this is the only muscle that opens the glottis, paralysis of this muscle may lead to asphyxiation and death.

In contrast, the role of the posterior cricoarytenoid muscle in phonation is not fully established. Some available data from the literature indicate that this muscle participates in the production of unvoiced sounds (e.g. the letters that do not require a vibration of the vocal cords).

Check out our learning materials about the larynx and then test your knowledge on the vocal cords.