1. The intrinsic laryngeal muscles may be divided into three functional groups: (i) muscles varying the rima glottidis (the transverse arytenoid as well as the lateral and posterior cricoarytenoid muscles); (ii) muscles regulating tension in the vocal ligaments (i.e. the cricothyroid, posterior cricoarytenoid as well as the compound thyroarytenoid and vocalis muscles) and (iii) muscles modifying the laryngeal inlet (the so-called ‘sphincter aditus’, which is formed by the oblique arytenoid and aryepiglottic muscles and counteracted by the thyroepiglottic muscle).