The posterior cricoarytenoid muscles are extremely small, paired muscles that extend from the posterior cricoid cartilage to the arytenoid cartilage

Arytenoid cartilage

The arytenoid cartilages are a pair of small three-sided pyramids which form part of the larynx, to which the vocal folds are attached...

s in the larynx

Larynx

The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...

. By rotating the arytenoid cartilages laterally, these muscles abduct the vocal cords and thereby open the rima glottidis

Rima glottidis

The rima glottidis is the opening between the true vocal cords and the arytenoid cartilages.It is normally subdivided into two parts, that between the arytenoid cartilages is called the intercartilaginous part , and that between the vocal folds the intermembranous part or glottis vocalis.It is...

. Their action opposes the lateral cricoarytenoid muscle

Lateral cricoarytenoid muscle

The lateral cricoarytenoid muscles extend from the lateral cricoid cartilage to the ipsilateral arytenoid cartilage. By rotating the arytenoid cartilages medially, these muscles adduct the vocal cords and thereby close the rima glottidis, protecting the airway...

s. The posterior cricoarytenoid muscles receive innervation from the recurrent laryngeal branch

Recurrent laryngeal nerve

The recurrent laryngeal nerve is a branch of the vagus nerve that supplies motor function and sensation to the larynx . It travels within the endoneurium...

 of the vagus nerve

Vagus nerve

The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...

(CN X).

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.