Which cartilage of the larynx is unique in forming a complete anatomical ring, and what is the practical consequence of this feature?

• A Thyroid cartilage; it allows rapid expansion during airway oedema
• B Arytenoid cartilage; it anchors the posterior commissure
• C Epiglottic cartilage; its elastic framework resists compression
• D Cricoid cartilage; circumferential oedema here rapidly narrows the only rigid complete airway ring ✓

Explanation

The cricoid is the only cartilage of the airway that forms a complete ring, signet-ring shaped with a tall posterior lamina and narrow anterior arch. Because there is no gap for expansion, even mild subglottic mucosal oedema in a child produces disproportionate narrowing and stridor, which is why subglottic stenosis and croup localize here. The thyroid cartilage is open posteriorly and the epiglottis is a leaf-like elastic structure.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.