LARYNX (Neo-Lat., from Gk. Xdpu-yE, lar ynx, larynx). The organ of voice. It also takes a part in the respiratory process, as all air pass ing either to or from the lungs must pass through it. It is a complex piece of mechanism resembling a box composed of pieces of cartilage, which may be moved on each other, and inelosing the mem branous bands (the ehorda. rocates) IT which the vocal vibrations are produced. It is situated between the trachea, or windpipe, and the base of the tongue. at the upper and front part of the neck, where it a considerable projec tion (especially in men) in the middle line; it opens superiorly into the pharynx, or throat, and inferiorly into the windpipe. The cartilages of which the skeleton of the larynx is composed are nine in number; viz. the thyroid and the cricoid cartilages. the epiglottis, the two aryte nob] and the two cuneiform cartilages, and the two eornienla larynyis, The thyroid (Gr., shicld-like) cartilage eon sists of two square plates of cartilage united in front at an acute angle, which forms the projec tion which is commonly known as the poinunt• Adawi, or Adam's apple. Each of these plates is prolonged at the upper and lower posterior cor ners. The thyroid cartilage forms almost the whole of the anterior and lateral walls of the la 'Tux.
The ericuid (Gr., ring-like) cartilage is a ring whose lower margin is parallel to the first ring of the trachea. to which it is united by fibrous mendirane. Its upper border is connected in front with the lower border of the thyroid car tilage by a thick yellow fibrous tissue. It pre sents two articular surfaces on either side; viz. a lower one. which articulates with the inferior corona of the thyroid cartilage. and an upper one, which is oval in form and supports an aryte noid cartilage. The arytenoid (Ur.. ladle-like) cartilages are pyramidal bodies resting on the oval articular surfaces at the upper and pos terior part of the cricoid cartilage. When in situ, they present a concave posterior surface. From their connection with the vocal cords, and front their great mobility as compared with the two larger cartilages, the arytenoids play a very important part in the mechanism of the larynx. The epiglottis is a very flexible cartilaginous valve. situated at the base of the tongue, and i•overing the opening of the larynx. Its direction is vertical, except during deglutition. when it becomes horizontal. It is attached inferiorly. by a kind of pedicle. to the angle of the thyroid
cartilage. Upon removing the investing muffins membrane, the cartilage is found to he perforated by numerous foramina. Each perforation admits sonic fasei•uli of yellow, elastic, ligamentous tissue, \Odell expands on its anterior a.peet and secures the return of the epiglottis to its vertical position, independently of any museular action. The cornicula laryngis are two small tibro-ear Hinges which articulate with the apices of the arytenoids. The cuneiform cartilages lie on either side in the fold of mucous membrane ex tending from the epiglottis to the Such is the skeleton of the larynx which hangs from the hyoid bone, with which it is connected by the thyro-hyoid ligament and certain muscles.
The various cartilages are connected one to another by ligaments, the chief of which are those known as the true and false vocal cords. In their quiescent state the true vocal cords not lie parallel to each other, lint converge from forward. The length of the vocal cords is greater in the adult male than in the adult female. in the ratio of three to two. in infancy they are very short, and increase regularly from that period to the age of puberty. The mucous membrane of the larynx is part of the great res piratory tract (see :Mucous INIEMBRANE) and is remarkable for its great sensibility.
The length of the chink or aperture of the glottis, Nvhieli is directed horizontally from be fore backward, varies, like the vocal cords, until the period of puberty, when its length in the male undergoes a Jsuilden development, while in the female it remains stationary. In the adult male it is about it lines in length.
The larynx is provided with two sets of mus cles; viz. the extrinsic, by which the whole organ is elevated or depressed. and the intrinsic, which regulate the movements of the various segments of the organ in relation to one another. By the action of these latter muscles. aided in some cases by the extrinsic muscles, the tension of the vocal cords may be increased or diminished, and the size of the opening of the glottis regu lated at will.
The nerves of the larynx are derived from the superior and inferior laryngeal branches of the pneumogastrie or vagns nerve. The superior braneh is for the most part sensory (being main ly distributed to the minions membrane), while the inferior brawl' communicates motor power to all the intrinsic muscles except the eri•o thyroid.