Posterior cricoarytenoid muscle

The posterior cricoarytenoid muscles are small, paired intrinsic muscles of the larynx that extend between cricoid cartilage to the arytenoid cartilages in the larynx.
Structure.
Origin and Insertion.
The posterior cricoarytenoid originates from the posterior surface of the posterior quadrate lamina of the cricoid cartilage. It inserts onto the posterior surface of the muscular process of the arytenoid cartilage. 
Nerve supply.
The posterior cricoarytenoid muscles are innervated by the recurrent laryngeal nerve, a branch of the vagus nerve (CN X).
Function.
The posterior cricoarytenoid muscles are the only muscles to open the vocal cords. By rotating the arytenoid cartilages laterally, these muscles abduct the vocal cords and thereby open the rima glottidis. Their action opposes the lateral cricoarytenoid muscles.
Clinical significance.
Paralysis of the posterior cricoarytenoid muscles may lead to asphyxiation as they are the only laryngeal muscles to open the true vocal folds, allowing inspiration and expiration.