THE LARYNX 1169 



The Epiglottis (cartilago epiglottica) (Figs. 882 and 883) is a thin, flexible lamella 

 of fibrocartilage, of a yellowish color, shaped like a leaf, and projecting behind the 

 tongue in front of the superior opening of the larynx. The projecting extremity is 

 broad and rounded; its attached part or apex (petiolus epiglottidis) is long, narrow, 

 and connected to the receding angle between the two alae of the thyroid cartilage, 

 just below the median notch, by a ligamentous band, the thyroepiglottic ligament 

 (Fig. 884). The lower part of its anterior surface is connected to the upper border 

 of the body of the hyoid bone by an elastic ligamentous band, the hyoepiglottic 

 ligament. 



Its anterior or lingual surface is curved forward, toward the tongue, and covered 

 at its upper, free part by mucous membrane, which is reflected on to the sides and 

 base of the organ, forming a median and two lateral folds, the glossoepiglottic 

 folds (Fig. 887); the lateral folds are partly attached to the wall of the pharynx. 

 The depressions between the epiglottis and base of the tongue on each side of the 

 median fold are named the valleculae. The lower part of the anterior surface of 

 the epiglottis lies behind the hyoid bone, the thyrohyoid membrane, and upper 

 part of the thyroid cartilage, but is separated from these structures by a mass of 

 fatty tissue. 



Its posterior or laryngeal surface is smooth, concave from side to side, concavo- 

 convex from above downward; its lower part projects backward as an elevation, 

 the tubercle or cushion (tuberculum epiglotticum) (Fig. 883). When the mucous 

 membrane is removed, the surface of the cartilage is seen to be indented by 

 a number of small pits, in which mucous glands are lodged. To its sides the 

 arytenoepiglottic folds are attached (Fig. 887). 



Structure. The cornicula laryngis and cuneiform cartilages, the epiglottis, and the apices 

 of the arytenoids at first consist of hyaline cartilage, but later elastic fibres grow in from the 

 perichondrium, and eventually they are converted into yellow fibrocartilage; they show little 

 tendency to calcification. The thyroid, cricoid, and the greater part of the arytenoids consist 

 of hyaline cartilage, and become more or less ossified as age advances. Ossification commences 

 about the twenty-fifth year in the thyroid cartilage, somewhat later in the cricoid and aryte- 

 noids ; by the sixty-fifth year these cartilages may be completely converted into bone. 



Ligaments. The ligaments of the larynx are extrinsic i. e., those connecting 

 the thyroid cartilage and epiglottis with the hyoid bone, and the cricoid cartilage 

 with the trachea; and intrinsic, those which connect the several cartilages of the 

 larynx to each other. 



Extrinsic Ligaments. The ligaments connecting the thyroid cartilage with the 

 hyoid bone are four in number the thyrohyoid membrane, the two lateral 

 thvrohvoid ligaments, and the hyoepiglottic ligament. 



The Thyrohyoid Membrane (membrana hyothyreoided) (Fig. 884) is a broad, 

 fibroelastic, membranous layer, attached below to the upper border of the thyroid 

 cartilage, and above to the upper margin of the posterior surface of the body and 

 greater cornua of the hyoid bone, thus passing behind the posterior surface of 

 the hyoid, and being separated from it by a synovial bursa (bursa m. sternohyoidei), 

 which facilitates the upward movement of the larynx during deglutition. It 

 is thicker in the middle line than at either side. This thickening is due to elastic 

 fibres, and constitutes the middle thyrohyoid ligament (ligamentum hyothyreoideum 

 medium). On each side the posterior extremity of the membrane is thickened 

 by elastic fibres, constituting the lateral thyrohyoid ligament (liqamentum hyothy- 

 reoideum laterale}. The thyrohyoid membrane is pierced on each side by the supe- 

 rior laryngeal vessels and the internal branch of the superior laryngeal nerve. The 

 anterior surface of the thyrohyoid membrane is in relation with the Thyrohyoid, 

 Sternohyoid, and Omohyoid muscles and with the body of the hyoid bone. The 

 two lateral ligaments are rounded, elastic cords, which pass between the superior 



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