Posterior cricoarytentoid muscle

The posterior cricoarytenoid muscle is a broad, fan-shaped intrinsic muscle of the larynx and the sole abductor of the vocal folds, making it essential for maintaining an open airway during breathing.

Origin

Posterior cricoarytenoid muscle originates from the posterior surface of the lamina of the cricoid cartilage.

Insertion

The muscle fibres pass superiorly and laterally to insert into the muscular process of the arytenoid cartilage.

Innervation

The muscle is innervated by the recurrent laryngeal nerve, a branch of the vagus nerve (cranial nerve X).

Action

When the posterior cricoarytenoid contracts, it rotates the arytenoid cartilages laterally, moving the vocal processes apart and thereby abducting the vocal folds to widen the rima glottidis—the space between the vocal folds. This action is crucial for inspiration and phonatory control.

Clinically, bilateral paralysis of the posterior cricoarytenoid muscles, as may occur with recurrent laryngeal nerve injury, can cause airway obstruction due to the inability to abduct the vocal folds.