The paired quadrangular membranes connect the epiglottis and adjacent thyroid cartilage (near the angle) to the corniculate cartilages and the lateral surfaces of the arytenoids. The free superior margins of the quadrangular membranes form the aryepiglottic folds. The free, slightly thickened inferior borders of the quadrangular membranes form the ventricular ligaments of the false folds.