The Human Body

Larynx

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Larynx, hollow chamber in which the voice is produced, at the front or upper part of the windpipe of mammals, frogs, and toads; it is also called the voice box. In mammals it leads from the lower portion of the pharynx to the trachea and is situated in front of or ventral to the esophagus, behind the skin and connective tissue of the throat. The larynx is supported by ligaments from the hyoid bone, situated at the base of the tongue.

The skeletal structure of the larynx is made up of three large cartilaginous structures, the epiglottis, thyroid cartilage, and cricoid cartilage, and of several pairs of small cartilages, the most important of which are known as arytenoid cartilages. The epiglottis is a broad cartilage attached in front to the top of the thyroid cartilage. The epiglottis swings over the opening from the pharynx into the voice box. When an animal swallows, the larynx is raised to press against the epiglottis and root of the tongue, preventing food from entering the air passages. Just below the epiglottis is the angular thyroid cartilage, composed of two vertical plates that join in the front of the neck. The junction of these plates causes the projection commonly known as the Adam's apple, so called because of the legend, referred to in Genesis 3:6, of the apple that lodged in Adam's throat. The rear portions of the thyroid cartilage grip the circular cricoid cartilage, which keeps the laryngeal passageway open at all times. On each side of the rear upper border of the cricoid cartilage is a small, movable arytenoid cartilage.

In the human larynx, two pairs of vocal cords are present. They are made of elastic connective tissue covered by folds of mucous membrane. One pair, the false vocal cords, extends from the epiglottis to the angle of the thyroid cartilage; these cords narrow the glottis (the pharyngeal opening of the larynx) during swallowing. Below the false cords are the true vocal cords, extending from the arytenoid cartilages to the angle of the thyroid cartilage. Vibration of this pair of cords by air passing out of the lungs causes the formation of sounds that are amplified by the resonating nature of the voice box. The pitch of the sound is voluntarily controlled by muscles that rotate the arytenoid cartilages toward the center of the body (slackening and lengthening the cords) for low tones, and toward the sides of the body (shortening the cords and pulling them taut) for high-pitched tones. The extent of the angle formed by the plates of the thyroid cartilage determines the depth of the human voice. The angle decreases in males at puberty, causing decreased tension of the vocal cords and a consequently deeper voice, and increases in most females at puberty, causing increased tension of the vocal cords.

The commonest affliction of the human larynx is inflammation, or laryngitis, often accompanying colds and accompanied by a temporary diminution or complete loss of voice. Other diseases commonly attacking the larynx include croup, diphtheria, and cancer. Laryngeal cancer has been shown to be caused by cigarette smoking and by the intake of large amounts of alcohol. Persons who smoke and drink excessively run an especially high risk of developing cancer of the larynx. It is treated by X-ray therapy, especially if diagnosed early, and by surgery. Surgical procedures include partial and total removal of the larynx.