Cricoid cartilage

At a glance

English

Cricoid cartilage

Latin (TA2)

Cartilago cricoidea

System

Cartilage

Region

Neck

Side

Single, on the midline

About the cricoid cartilage

The cricoid cartilage forms the lower part and much of the back of the larynx, and it is the one cartilage that encircles the airway completely. Its name means ring-shaped. Seen from the side it resembles a signet ring: a narrow band in front and at the sides, and a tall, broad plate, the lamina, behind. It lies below the thyroid cartilage at about the level of the sixth cervical vertebra, and the trachea hangs from it. Like the thyroid and arytenoid cartilages it is hyaline, so it tends to calcify or ossify with age.

In front, the median cricothyroid ligament (cricothyroid membrane) joins its upper border to the lower border of the thyroid cartilage, and at the back of each side a small facet articulates with the inferior horn of the thyroid at the cricothyroid joint. On the sloping upper border of the lamina are two oval facets for the bases of the arytenoid cartilages. Below, the cricotracheal ligament ties it to the top tracheal ring; that ring and those below are C-shaped and open behind, so the cricoid is the lowest complete support. The thyroid gland is close by: its isthmus lies a little below the cricoid, and its lobes climb on either side of it towards the thyroid cartilage.

The cricoid is the foundation on which the other laryngeal cartilages move. Cricothyroid runs from its arch to the thyroid and tilts the two cartilages to lengthen the vocal folds, while posterior and lateral cricoarytenoid arise from the lamina and arch and swing the arytenoids to open or close the glottis. The oesophagus begins behind the lamina, and the inferior constrictor of the pharynx, through its cricopharyngeal part, is attached to its sides.

In the neck, the firm cricoid ring is felt below the softer gap of the cricothyroid membrane, which is the site of an emergency cricothyroidotomy. During rapid sequence induction of anaesthesia, pressure on the cricoid (Sellick's manoeuvre) was used to squeeze the oesophagus against the spine and prevent stomach contents from reaching the airway; its value is now debated because it is often applied wrongly and may push the oesophagus aside or narrow the glottis. Part of the cartilage can be removed surgically to relieve a narrowing of the airway at this level.

Attachments and function

Attaches from

Linked above to the thyroid cartilage through the cricothyroid membrane in front and the paired cricothyroid joints behind.

Attaches to

Tied below to the top ring of the trachea by the cricotracheal ligament; its lamina carries the arytenoid cartilages.

Function

Forms a rigid complete ring at the base of the larynx, keeps the airway open, and provides the base and joints on which the thyroid and arytenoid cartilages move.

Nerve supply

Its muscles are supplied by the recurrent laryngeal nerve, except cricothyroid, which is supplied by the external laryngeal nerve.

Blood supply

The cricothyroid branch of the superior thyroid artery and laryngeal branches of the inferior thyroid artery.