larynx [key], organ of voice in mammals. Commonly known as the voice box, the larynx is a tubular chamber about 2 in. (5 cm) high, consisting of walls of cartilage bound by ligaments and membranes, and moved by muscles. The human larynx extends from the trachea, or windpipe. In humans, part of the structure may protrude noticeably at the front of the neck, forming the so-called Adam's apple. Within the larynx lie the vocal cords, or vocal folds, a pair of elastic folds in the lining of mucous membrane. During silent breathing, the vocal cords rest along the larynx walls, leaving the air passage fully open. During speech, the cords are stretched across the larynx; air released from the lungs is forced between the cords, causing them to vibrate and so produce voice. Various muscles adjust the tension of the cords as well as the space between them, thus varying the pitch of the sounds produced. The more taut the cords, the higher the pitch. Since men's larynges are usually larger than women's, male vocal cords tend to be longer and the male voice is thus deeper. Growth may double the length of the vocal cords in the male adolescent; hence his dramatic “change of voice.” Over the vocal cords extend parallel bands of protective tissue, the false vocal cords. The larynx controls pitch and volume of vocal utterances—it produces initial sounds, while the articulation of these sounds results from the manipulation of teeth, tongue, palate, and lips. Above them, at the opening of the larynx into the throat, hangs the epiglottis, a flap of cartilage that helps to seal off the lower respiratory tract during swallowing so that food and other foreign elements do not enter it.
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