THE LARYNX 



1167 



Epiglottis. 



middle portion of the cricothyroid membrane (membrana cricothyroid ea); and, on 

 either side r by the Cricothyroid muscle. 



The posterior borders (Fig. 882) are thick and rounded, and each terminates 

 above, in a superior cornu (cornu superius), and below, in an inferior cornu (cornu 

 iiiferius). The two superior cornua are long and narrow, directed upward, back- 

 ward, and inward, and terminate in conical extremities, which give attachment 

 to the lateral thvrohvoid ligaments. The two inferior cornua are short and thick; 

 they pass downward, with a slight 

 inclination forward and inward, 

 and each presents on its inner sur- 

 face a small oval articular facet for 

 articulation with the side of the 

 cricoid cartilage (Fig. 881). The 

 posterior border receives the in- 

 sertion of the Stylopharvngeus and 

 Palatopharyngeus muscles on each 

 side. 



During infancy the alse of the thyroid 

 cartilage are joined to each other by a 

 narrow, lozenge-shaped strip, named the 

 intrathyroid cartilage. This strip ex- 

 tends from the upper to the lower border 

 of the thyroid cartilage in the middle 

 line, and is distinguished from the ala? 

 by being more transparent and more 

 flexible. 



The Cricoid Cartilage (cartilago 

 cricoidea) (Figs. 881 and 882) is so 

 called from its resemblance to a 

 signet ring (^or'xoc, a ring). It is 

 smaller, but thicker and stronger 

 than the thyroid cartilage, and 

 forms the lower and back part of 

 the cavity of the larynx. It is hya- 

 line cartilage, and consists of two 

 parts a quadrate portion, situated 

 behind, and a narrow ring, or arch, 

 one-fourth or one-fifth the depth 

 of the posterior part, situated in 

 front. The posterior square por- 

 tion rapidly narrows at the sides of 

 the cartilage, at the expense of the 

 upper border, into the anterior 

 portion. It represents a modified 

 tracheal ring. 



Its posterior portion, or lamina (lamina cartilaginis cricoideae), is very deep and 

 broad, and measures from above downward about an inch (2.5 cm.); it ^re- 

 sents, on its posterior surface, in the middle line, a vertical ridge for the attach- 

 ment of the longitudinal fibres of the oesophagus, and on either side a broad 

 depression for the Cricoarytenoideus posticus muscle. 



Its anterior portion, or arcus (arcus cartilaginis cricoideae), is narrow and convex, 

 and measures vertically about one-fourth or one-fifth of an inch (5 to 6 mm.), 

 it affords attachment externally in front and at the sides to the Cricothyroid 

 muscles, and, behind, to part of the Inferior constrictor. 



Posterior 

 surface. 



Arytenoid cartilages, base. 



POSTICUS ET LATERALIS 



Cricoid. 



Articular facet for 

 arytenoid cartilage. 



A rticida r facet for 



inferior cornu of 

 thyroid cartilage. 



FIG. 882. The cartilages of the larynx. Posterior view. 



