Cricoid Cartilage

1. Overview

The cricoid cartilage is a complete ring of cartilage located in the larynx, playing a crucial role in airway structure, voice production, and airway protection. It is the only complete cartilaginous ring of the airway and forms the base of the laryngeal skeleton. The cricoid cartilage serves as the attachment site for multiple muscles, ligaments, and other cartilages involved in phonation and breathing. It also marks the transition from the upper airway (larynx) to the lower airway (trachea).

2. Location

The cricoid cartilage is situated:

• Below the thyroid cartilage

• Above the first tracheal ring

• At the level of the C6 vertebra in adults

It forms the inferior portion of the larynx and encircles the airway completely, unlike other laryngeal cartilages which are incomplete posteriorly.

3. Structure

The cricoid cartilage resembles a signet ring, being narrow anteriorly and broad posteriorly. Structural features include:

• Anterior arch: The thin, curved front portion of the ring.

• Posterior lamina: A broad, flat structure forming the back wall, thicker and taller than the arch.

• Articulations:

  • Superiorly with the inferior horns of the thyroid cartilage at the cricothyroid joints

  • Posteriorly with the arytenoid cartilages at the cricoarytenoid joints

• Composition: Made of hyaline cartilage, which may calcify or ossify with age.

4. Function

The cricoid cartilage performs several essential functions:

• Airway support: Maintains the patency and structural integrity of the upper airway.

• Muscle attachment: Anchors intrinsic and extrinsic muscles of the larynx that regulate vocal cord movement and airway diameter.

• Phonation support: Supports the vocal fold position via its articulation with the thyroid and arytenoid cartilages.

• Swallowing and airway protection: Assists in closing the glottis during deglutition.

5. Physiological Role(s)

Physiologically, the cricoid cartilage contributes to:

• Phonation: By supporting the cricothyroid and cricoarytenoid joints, it helps modulate tension and position of the vocal cords for voice production.

• Breathing: It acts as a movable platform that allows opening (abduction) and closing (adduction) of the vocal folds through attached muscles.

• Cough and Valsalva maneuver: Provides rigid support against which increased intrathoracic pressure can build during coughing or straining.

• Swallowing reflexes: Works with surrounding structures to prevent aspiration by coordinating laryngeal elevation and glottic closure.

6. Clinical Significance

Cricoid Pressure (Sellick Maneuver)

Used during rapid sequence intubation to compress the esophagus against the cricoid cartilage and prevent aspiration. However, its effectiveness and safety are debated, especially in unconscious patients.

Intubation Landmark

The cricoid cartilage is a palpable external landmark used to identify the larynx and guide tracheal intubation. It lies just inferior to the thyroid cartilage (“Adam’s apple”).

Cricothyrotomy

In emergency airway access, a surgical opening is created through the cricothyroid membrane (just above the cricoid cartilage). The cricoid cartilage serves as the inferior boundary for this procedure. It is not typically punctured itself due to its cartilaginous thickness.

Tracheal Stenosis and Tumors

The cricoid cartilage may be involved in subglottic stenosis, especially after prolonged intubation or trauma. As a rigid structure, its involvement makes the stenosis more difficult to manage surgically.

Cricoarytenoid Arthritis

In conditions like rheumatoid arthritis, inflammation can involve the cricoid’s articulation with the arytenoid cartilage, leading to:

• Hoarseness

• Painful phonation

• In severe cases, airway obstruction

Pediatric Considerations

In infants and young children, the cricoid cartilage is the narrowest part of the airway, making it a common site for obstruction and edema in conditions like:

• Croup

• Subglottic stenosis

• Airway burns