[TA] portion of the fibroelastic membrane of the larynx that lies superior to the laryngeal ventricle; its slightly thickened inferior edge, the vestibular ligament, underlies the vestibular fold of the larynx; it attaches anteriorly to the epiglottis and posteriorly to the lateral margin of the arytenoid and corniculate cartilages; its upper portion underlies the mucosa of the aryepiglottic fold, which separates the laryngeal vestibule from the piriform fossa of the laryngopharynx. SYN: membrana quadrangularis [TA], Tourtual membrane.