Posterior cricoarytenoid muscle
Posterior cricoarytenoid is a paired muscle that belongs to the group of intrinsic muscles of the larynx. Together with the other muscles from this group, it has a role in adjusting the length and tension of the vocal cords by which it modulates the process of phonation.
|Origin||Posterior surface of cricoid lamina|
|Insertion||Muscular process of arytenoid cartilage|
|Action||Abducts and lengthens vocal folds, opens glottis|
|Innervation||Inferior laryngeal nerve (of recurrent laryngeal nerve (CN X))|
|Blood supply||Laryngeal branches of the superior and inferior thyroid arteries|
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.
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.
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).
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.
A failure of posterior cricoarytenoid muscle function is usually due to damage to the recurrent laryngeal nerve. Most often, this injury occurs during thyroidectomy operations (removal of the thyroid gland), or due to diseases of the surrounding organs that compress or infiltrate the nerve (e.g. bronchial tumors or goiter of the thyroid gland).
Typical symptoms of unilateral recurrent laryngeal nerve palsy are hoarseness and reduced vocal stamina, due to loss of function of the majority of the intrinsic muscles. Bilateral palsy of this nerve causes paralysis of the posterior cricoarytenoid muscle which can be a life-threatening condition due to possible asphyxia. A diagnosis is usually established after performing a physical examination, laryngoscopy and laryngeal electromyography.