Quadrangular membrane

At a glance

English

Quadrangular membrane

Latin (TA2)

Membrana quadrangularis

System

Ligament

Region

Neck

Side

Paired, left and right

About the quadrangular membrane

The fibroelastic membrane of the larynx lies just beneath the lining mucosa and has two parts. Below is the conus elasticus, which ends in the vocal ligaments. Above is the quadrangular membrane, a paired, four-sided sheet that stiffens the walls of the laryngeal vestibule, the part of the airway between the inlet and the vestibular folds.

Each membrane stretches from the side of the epiglottis in front to the anterolateral surface of the arytenoid cartilage and the corniculate cartilage behind. Its four borders give it its name. The upper border is free and runs back and down from the epiglottis to the arytenoid; covered with mucosa it forms the aryepiglottic fold, which outlines the laryngeal inlet. The lower border is also free; thickened, it is the vestibular ligament, and with its mucosal covering it becomes the vestibular fold (false vocal cord), which sits above the true vocal fold. The front border attaches to the epiglottis and the back border to the arytenoid.

Small pieces of elastic cartilage, the cuneiform cartilages, are usually embedded in the membrane near the back of the aryepiglottic fold, where they raise little bumps visible on laryngoscopy and help support the fold. Outside the membrane lies the piriform recess of the pharynx, where swallowed fish bones can lodge; inside it is the vestibule. Between the vestibular and vocal folds the mucosa pouches outwards into the laryngeal ventricle and saccule.

The membrane gives shape to the upper larynx and helps keep the inlet open for breathing. During swallowing, the aryepiglottic folds draw together and the vestibular folds close, sealing the airway above the vocal folds. Its mucosa is supplied with sensation by the internal laryngeal nerve, so contact with food here triggers coughing. Tumours of the supraglottic larynx spread along this membrane.

Attachments and function

Attaches from

The lateral margin of the epiglottis.

Attaches to

The anterolateral surface of the arytenoid cartilage and the corniculate cartilage.

Function

Supports the walls of the laryngeal vestibule and forms the core of the aryepiglottic and vestibular folds, which help seal the airway in swallowing.

Nerve supply

Its mucosa is supplied by the internal branch of the superior laryngeal nerve.

Blood supply

The superior laryngeal artery, from the superior thyroid artery.