ANATOMY & PHYSIOLOGY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site larynx Larynx. Cross-sectional diagram Known commonly as the voice box or "Adam's apple", an organ in the neck of humans and other mammals that is involved in the production sound and also serves to protect the upper part of the trachea (windpipe). The larynx houses the vocal cords and is shaped like a funnel, with walls of cartilage and a highly complicated system of muscles. It lies just below where the tract of the pharynx splits into the trachea and the esophagus, extending from the fourth to the sixth vertebral levels. The larynx is often divided into three sections: sublarynx, larynx, and supralarynx. It is formed by nine cartilages that are connected to each other by muscles and ligaments. Movement of these cartilages alters the tension of the vocal cords, which changes the pitch of the sound emitted by the vocal cords when they vibrate. Functions of the larynx The most important function of the larynx is to prevent choking. When a person is not eating or drinking, the epiglottis remains uprights, keeping the larynx open as part of the airway to the lungs. As soon as swallowing begins, the epiglottis descends like a lid over the larynx, directing food to either side. Closure of the vocal cords also helps protect the airway. The food or drink then passes down the esophagus to the stomach. The secondary function of the larynx is voice production. How the larynx produces sounds a) epiglottis; b) aperture of the glottis; c) arytenoid muscles; d) trachea The opening of the larynx, i.e. the space between the vocal cords is called the glottis. When at rest, and with normal breathing, it is a triangular orifice through which the air passes freely. When a sound is to be made, the arytenoid muscles (see artwork) act so as to twist the arytenoid cartilages, and these stretch or slacken the vocal cords, which can assume about 170 different positions. At the same time, the glottis itself is narrowed to a slit, the size of which regulates the rate at which air passes through the larynx from the lungs. The accurately controlled current of air makes the vocal cords vibrate, and so sounds are produced. As produced by the vocal cords they would be too weak and faint to be heard, but the hollows of the respiratory system, in the trachea, the pharynx, the larynx itself, and the nose and mouth, act as resonators which strengthen and modify the sound. The chest also acts as a resonator and amplifies the sound just as the body of a violin does. How the larynx helps produce words In the case of humans, the sounds of the voice can be shaped to form words, which are made up of vowels and consonants. The shaping is done by the muscles of the mouth, palate, lips, and tongue. Vowels are accompanied by vibration of the larynx and the sound passes unobstructed through the mouth. Consonants are formed mainly by the alteration of the laryngeal sound by the tongue, teeth, lips, and palate. A word cannot be made up of consonants alone, because most of these cannot be voiced unless a vowel precedes or follows them. Some consonants are called labials (Latin labia, lip) because they are formed by the lips; it is impossible to say b, p, f, m, or v with your mouth alone. Others (d, t, l, n, r, s, z, ch, j) are linguals, requiring the use of the tongue (Latin lingua, tongue). G, q, and k are gutterals, made with the back of the palate (Latin gutter, throat). The pitch of the voice depends on the frequency of vibrations of the vocal cords. If they are at normal tension the vibrations are about 80 per second; if the cords are tightly stretched they are more rapid, up to 1,000 per second. Related category    • ANATOMY AND PHYSIOLOGY Sources: National Cancer Institute; Knowledge magazine p. 304 Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP