Muscle · Neck

Posterior cricoarytenoid

Musculus cricoarytenoideus posterior

The single most important muscle in the larynx, because it is the only one that opens the vocal folds. It is a flat triangular muscle on the back of the cricoid cartilage, its fibres converging upwards and outwards onto the same arytenoid process that the lateral cricoarytenoid pulls the other way. Contracting it rotates the arytenoid outwards, swinging the back ends of the vocal folds apart and widening the airway — which is what happens with every breath in, more strongly the harder the breathing. Every other intrinsic muscle of the larynx closes the folds in one way or another; this one alone opens them, so the airway depends on it in a way it does not depend on any of its neighbours.