Median cricothyroid ligament

At a glance

English

Median cricothyroid ligament

Latin (TA2)

Ligamentum cricothyreoideum medianum

System

Ligament

Region

Neck

Side

Single, on the midline

About the median cricothyroid ligament

Between the thyroid cartilage above and the cricoid cartilage below lies a fibroelastic sheet, the cricothyroid membrane (also called the cricovocal membrane). In the midline at the front this sheet is greatly thickened into the median cricothyroid ligament. The thinner side parts, which curve upwards inside the larynx, form the conus elasticus, sometimes called the lateral cricothyroid ligaments.

The median ligament is a flat, tough band of white fibrous tissue. It is narrow above, where it attaches to the lower border of the thyroid cartilage near the midline, and widens on its way down to the top edge of the cricoid arch. It can be felt in the living neck as a soft depression below the laryngeal prominence (Adam's apple) and above the firm ring of the cricoid. The conus elasticus on each side runs from the top of the cricoid up to the vocal ligament; the vocal ligament is in fact the thickened upper free edge of the cone, stretched between the vocal process of the arytenoid cartilage behind and the inner angle of the thyroid cartilage in front.

Several structures sit close by. The cricothyroid muscles cover the sides of the membrane, and the small cricothyroid arteries, branches of the superior thyroid arteries, often cross it near its upper border. A small prelaryngeal (Delphian) lymph node lies in front of it, and enlargement of this node can signal spread of thyroid or laryngeal disease.

The ligament holds the two cartilages from separating too far while still allowing the thyroid to tilt on the cricoid, the movement that tenses the vocal folds. Its main clinical value is as an emergency airway. When the upper airway is blocked above the vocal folds and an endotracheal tube cannot be passed, a cut or needle through the ligament (cricothyrotomy) opens a direct route into the subglottic airway. The same landmark is used in many domestic animals, including dogs, cats and horses, for sampling from the airway.

Attachments and function

Attaches from

The lower border of the thyroid cartilage in the midline.

Attaches to

The upper border of the arch of the cricoid cartilage.

Function

Stops the thyroid and cricoid cartilages pulling apart too far, while allowing the thyroid to tilt forwards on the cricoid.

Nerve supply

Sensory branches of the recurrent laryngeal nerve below the vocal folds; the external laryngeal nerve supplies the cricothyroid muscle beside it.

Blood supply

The cricothyroid branches of the superior thyroid arteries, which often cross it.