Quadrangular Membrane

Description

Arising from the lateral margins of the epiglottis, the quadrangular membrane is shown as a paired fibroelastic sheet descending inferiorly and posteriorly toward the arytenoid cartilages. Its thickened superior free edge forms the aryepiglottic fold, while the inferior free edge condenses into the vestibular ligament that runs anterior to the vocal fold and defines the superior boundary of the laryngeal ventricle. Laterally, the membrane sits deep to the thyroid cartilage and adjacent to the inner surface of the thyrohyoid membrane region, with intrinsic laryngeal muscles bracketing it, including fibers of the thyroarytenoid and aryepiglottic muscles within the fold. Small structure, big consequence. Teaching the quadrangular membrane matters because it explains how the supraglottis seals and shapes airflow before the true vocal folds engage. Edema of the aryepiglottic folds and vestibular folds, such as in supraglottitis or allergic angioedema, can narrow the laryngeal inlet quickly, and this view clarifies why stridor can occur even when the vocal folds themselves remain mobile. It also anchors endoscopic orientation: the aryepiglottic fold forms the lateral boundary of the laryngeal aditus, and its relationship to the arytenoids guides safe passage during intubation and during microlaryngoscopy when assessing supraglottic masses. Use this illustration in head and neck anatomy teaching blocks, ENT surgical atlases, and speech science materials that need a clean distinction between vestibular ligament and vocal ligament, and between supraglottic closure mechanisms and phonatory structures. It also suits patient-facing education on supraglottic swelling and airway compromise when simplified labels are added. Anatomical accuracy verified by SciePro's Medical Advisory Board.