Larynx

The larynx sits in the front of the neck, below the hyoid bone and the root of the tongue and above the trachea, at about the level of the fourth to sixth cervical vertebrae. Its framework is nine cartilages joined by ligaments and muscles. The largest, the shield-like thyroid cartilage, forms the bump known as the Adam's apple; below it, the ring-shaped cricoid cartilage connects to the trachea; and above, the leaf-shaped epiglottis overhangs the entrance. Small paired arytenoid cartilages anchor and move the vocal cords.

The larynx has three jobs. It is an airway, keeping a passage open between the pharynx and the lungs. It is a guard: during swallowing it rises, the epiglottis folds down over its opening and the vocal folds close, so food is steered into the esophagus, and anything touching its lining triggers a cough. And it makes sound: the true vocal cords come together and vibrate as air from the lungs passes between them, while small muscles alter their tension to change pitch.

Its muscles are supplied by branches of the vagus nerve, chiefly the recurrent laryngeal nerve, and injury to that nerve during neck or thyroid surgery can leave a hoarse voice. Laryngitis, usually from infection or overuse, and laryngeal cancer, strongly linked to smoking, are its common disorders.