Larynx (voice box)

Function

The larynx is the airway's crossroads valve — a cartilage box (thyroid, cricoid, epiglottis, arytenoids) where the respiratory and digestive tracts intersect. Nine cartilages, suspended by the hyoid, move through a precise choreography: during swallowing the epiglottis folds down as the larynx rises, sealing the entrance against aspiration.

Inside, the vocal folds adduct for phonation — the cricothyroid and thyroarytenoid muscles tune their tension across three octaves while air passing between them makes them oscillate 100–1,000 times per second. The folds also guard the lungs: the cough reflex blasts foreign material clear at 160 km/h.

Blood supply

Superior and inferior laryngeal arteries.

Nerve supply

Superior laryngeal nerve (sensation above the folds) and recurrent laryngeal nerve (all intrinsic muscles except cricothyroid; sensation below).

Clinical relevance

Vocal cord paralysis

Recurrent laryngeal nerve injury (thyroid surgery, malignancy, aortic aneurysm) hoarsens the voice; bilateral palsy stridors the airway.

Laryngitis and croup

Inflammation swells the folds; children's narrow subglottis turns viral croup into a barking, stridorous emergency.

Related conditions

• Obstructive sleep apnoea
• Anaphylaxis