glottis

The glottis is the opening between the vocal folds (true vocal cords) within the larynx. It comprises the vocal folds themselves and the space between them, called the rima glottidis. The glottis forms the entrance to the lower respiratory tract and plays a central role in voice production and protection of the airway.

It is bounded anteriorly by the thyroid cartilage and posteriorly by the arytenoid cartilages. The size and shape of the glottic opening are controlled primarily by intrinsic laryngeal muscles: the posterior cricoarytenoid abducts the vocal folds to widen the glottis, while the lateral cricoarytenoid and the interarytenoid muscles adduct them to narrow or close it. The tension of the vocal folds, which affects pitch, is adjusted mainly by the cricothyroid muscle and by changes in vocal fold mass and stiffness. Phonation occurs when air from the lungs passes through the adducted, vibrating vocal folds.

During breathing, the glottis is typically open or widened to allow air to pass easily; during swallowing, the glottis closes to prevent aspiration. Many speech phenomena involve glottic configurations, such as glottal stops, glottalization, or voice onset with a glottal attack. Pathologies affecting the glottis or its nerves, such as laryngitis, vocal fold nodules, or recurrent laryngeal nerve palsy, can alter voice quality and airway protection.

Although the term glottis is most often used in human anatomy, it is a general term for the opening of the laryngeal cavity in many vertebrates, with variations in structure and function across species.