A re-appraisal of intrinsic laryngeal muscle action.

Anatomical dissection and electrical stimulation of three intrinsic laryngeal muscles, the lateral cricoarytenoid, posterior cricoarytenoid, and thyroarytenoid, have demonstrated findings that contradict current teaching on laryngeal muscle action. The posterior cricoarytenoid and the thyroarytenoid muscles demonstrated complexities of movement which have not been previously described. Both have three forces of action capable of moving the arytenoid cartilage in three directions. These directions of movement were dependent upon the finite anatomy of the cricoarytenoid joint. The lateral cricoarytenoid muscle, because of its attachments and the direction of its fibres, acts as both an abductor and a dynamic ligament in arytenoid cartilage movement.