larynx

The larynx, or voice box, is a cartilaginous and muscular organ in the neck that forms the upper part of the lower airway. It routes air from the pharynx to the trachea, produces sound, and protects the airway during swallowing. In adults it lies opposite the C3–C6 vertebrae.

Anatomy: The laryngeal skeleton comprises nine cartilages: three unpaired (epiglottis, thyroid, cricoid) and three paired (arytenoid, corniculate, cuneiform). The epiglottis and the vocal folds form the glottic opening, the rima glottidis. The larynx is suspended from the hyoid bone by extrinsic ligaments and membranes; intrinsic ligaments and joints allow movement of the vocal folds and cartilage.

Muscle: Intrinsic muscles adjust tension and position of the vocal folds (cricothyroid, thyroarytenoid including vocalis, posterior and lateral cricoarytenoid, interarytenoids). Extrinsic muscles position the larynx in the neck.

Innervation and blood supply: Motor and sensory innervation are mainly by branches of the vagus nerve: the superior laryngeal nerve (internal branch provides mucosal sensation above the vocal folds; external branch supplies the cricothyroid muscle) and the recurrent laryngeal nerve (motor to intrinsic muscles except cricothyroid; sensation below the vocal folds). Arterial supply comes from branches of the superior and inferior thyroid arteries.

Function: The larynx maintains airway protection during swallowing via the epiglottis and vocal fold adduction; it generates sound as air passes through the glottis, with pitch controlled by vocal fold tension and length; it participates in coughing and forced expiration.

Clinical relevance: Laryngitis, vocal nodules or polyps, and laryngeal cancer are common conditions. Laryngoscopy is used for examination; acute airway obstruction is a medical emergency.