Thyroid cartilage

At a glance

English

Thyroid cartilage

Latin (TA2)

Cartilago thyreoidea

System

Cartilage

Region

Neck

Side

Single, on the midline

About the thyroid cartilage

The thyroid cartilage is the biggest piece of the laryngeal skeleton and forms most of the front and side walls of the voice box. Its name comes from a Greek word meaning shield-shaped. It is made of hyaline cartilage and lies in front of the larynx at roughly the level of the fourth and fifth cervical vertebrae, above the thyroid gland. Unlike the cricoid below, it does not form a complete ring: it is open behind, where the pharynx lies.

It consists of two flat, four-sided plates, the laminae, which join in the midline in front and diverge backwards like the bow of a ship. Where they meet, the upper part of the angle juts forward as the laryngeal prominence, the Adam's apple, which is more pronounced in men because the angle between the plates is sharper. A V-shaped superior thyroid notch lies above the prominence, and a shallower inferior notch sits in the middle of the lower border. On the outer face of each lamina an oblique line runs downwards and forwards between a superior and an inferior tubercle. The back border of each plate is drawn out into two horns: a long, slender superior horn pointing up, and a short, thick inferior horn pointing down.

The whole upper border hangs from the hyoid through the thyrohyoid membrane, whose thickened back edge, the lateral thyrohyoid ligament, ends on the tip of the superior horn. The inferior horn carries a small facet on its inner side that meets the side of the cricoid at the synovial cricothyroid joint. Sternothyroid inserts and thyrohyoid and the inferior pharyngeal constrictor arise along the oblique line. Inside, the vocal and vestibular ligaments, the thyro-arytenoid muscles and the stalk of the epiglottis attach near the angle.

The cartilage shields the vocal folds, which lie directly behind its angle. When cricothyroid tilts the thyroid forwards on the cricoid at the cricothyroid joints, the distance to the arytenoids increases, the vocal folds stretch and the pitch of the voice rises. The prominence and notch are easily felt and guide the clinician to the cricothyroid membrane just below. It tends to calcify with age and can fracture in a blow to the front of the neck.

Attachments and function

Attaches from

Its upper border is suspended from the hyoid through the thyrohyoid membrane and its lateral thyrohyoid ligaments.

Attaches to

Its inferior horns articulate with the cricoid cartilage at the cricothyroid joints, and its lower border is joined to the cricoid in front by the median cricothyroid ligament.

Function

Forms and protects the front of the larynx, anchors the front ends of the vocal folds, and tilts on the cricoid to change vocal fold tension and voice pitch.

Nerve supply

Cricothyroid, which tilts it, is supplied by the external laryngeal nerve; the other intrinsic muscles attached to it by the recurrent laryngeal nerve.

Blood supply

The superior thyroid artery and its superior laryngeal and cricothyroid branches supply its perichondrium and the surrounding tissues.