larynx

larynx , 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.

larynx The larynx is the ‘voicebox’, the organ in the neck that plays a crucial role in speech and breathing. The channels for air and for food, which share the pharynx at the back of the nose and mouth, diverge at this point, leading respectively to the trachea and to the oesophagus. The opening for air through the larynx is known as the glottis, and the epiglottis, below and behind the tongue, plays a necessary part in closing off the glottis during swallowing.

The larynx has three important functions: control of the airflow during breathing, protection of the airway below it, and production of sound for speech. The main part of the framework of the larynx is the thyroid cartilage, and it is the front part of this that can easily be seen and felt as the ‘Adam's apple’. The larynx rests on the ring-shaped cricoid cartilage, and below this is the trachea. Above, and attached by ligaments to the larynx at the front, is the U-shaped hyoid bone that provides support and moves upwards with the larynx during swallowing. Halfway down the larynx the paired vocal folds (commonly known as the vocal cords), formed by ligaments covered with mucous membrane, project inwards from its wall. The vocal folds form a ‘V’ shape, open towards the back. At the rear end of each vocal fold are the small arytenoid cartilages. Many small muscles are attached to these, and their action can vary the size of the aperture, by pulling the arytenoids apart or drawing them nearer together, widening or narrowing the ‘V’. This movement occurs rhythmically during inhalation and exhalation in regular quiet breathing. Closure of the glottis occurs only momentarily during swallowing; abnormally, near-closure (laryngospasm) seriously obstructs breathing and causes stridor — high-pitched and noisy breathing.

During speech, singing, or playing a wind instrument, the size of the aperture is narrowed and varied, to produce sounds of different pitch. This increased resistance to airflow out of the lungs converts the flow to a rapid pulsation as it passes between the vocal folds; this produces sound that is then modified by the upper vocal tract.

Marjorie P. Lorch

larynx (voice-box) Triangular cavity located between the trachea and the root of the tongue. Inside it are the vocal cords, which are thin bands of elastic tissue. The vocal cords vibrate when outgoing air passes over them, setting up resonant waves that are changed into sound by the action of throat muscles and the shape of the mouth. Inflammation of the larynx and vocal cords is called laryngitis. Symptoms include sore throat, coughing and breathing difficulties. It is usually due to a respiratory tract infection.