glottidis

The glottidis, commonly referred to as the glottis, is the part of the larynx that includes the vocal folds (true vocal cords) and the opening between them, the rima glottidis. It forms the airway-opening at the laryngeal inlet and its size and shape change during respiration, phonation, and swallowing. In adults, the glottis is described as having a membranous (anterior) part and a cartilaginous (posterior) part.

Anatomy: The glottis is bounded by the two vocal folds anteriorly and laterally, and by the arytenoid cartilages posteriorly. The membranous glottis refers to the open portion between the vocal cords; the cartilaginous glottis refers to the opening between the arytenoid cartilages. Intrinsic laryngeal muscles control the position and tension of the vocal folds: the posterior cricoarytenoid abducts the cords to widen the glottis, whereas the lateral cricoarytenoid, interarytenoid, and thyroarytenoid muscles adduct them. The cricothyroid muscle adjusts tension and pitch.

Function: The glottis plays a central role in phonation, when the vocal folds vibrate as air passes through a closed or nearly closed glottis, producing voice. It also regulates airflow during breathing by abducting the cords to maximize airway. During swallowing, the glottis closes to protect the airway from aspiration.

Clinical relevance: Injury to the nerves supplying intrinsic laryngeal muscles, especially the recurrent laryngeal nerve, can alter glottic closure and voice quality, leading to hoarseness, breathy voice, or airway obstruction in bilateral paralysis. Other conditions affecting the glottis include laryngitis, vocal fold nodules or polyps, and tumors; evaluation typically involves laryngoscopy.