526 THE LARYNX. 



extremity has two tubercles, termed the superior and infe- 

 rior cornua. Each ala has an oblique line, dividing it into 

 two unequal parts, and giving attachment to the sterno- 

 thyroid, thyro-hyoid, and inferior constrictor muscles of 

 the pharynx. The superior cornua are connected by liga- 

 ments to the os-hyoides the inferior are articulated with 

 the cricoid. 



The thyroid is open behind, and encloses the sides of the 

 cricoid. Its posterior surface, behind the pomum, is concave 

 and has attached to it the chordas-vocales, and epiglottic 

 ligament. 



The cricoid, (*pcoj, ring, So^ like,) as its name implies, 

 is annular or ring-like in its form ; it is situated at the 

 lower and posterior portion of the larynx, giving that pro- 

 tection from the pressure of the parts behind, which the 

 thyroid does from that of the atmosphere in front. 



It is narrow before, and broad and vertical behind. Its 

 anterior surface is convex, and has the crico-thyroid mus- 

 FIG 159. cles attached to it. The posterior surface pre- 

 sents a depression for the crico-arytenoidei 

 postici, and along its middle, a vertical ridge 

 giving attachment to some fibres of the oeso- 

 phagus. The upper margin is horizontal, and 

 has two convex, smooth surfaces, for articulation with the 

 bases of the arytenoid cartilages. The lower margin is 

 circular, and connected to the first ring of the trachea. 

 The arytenoid cartilages (apv^a^a, a pitcher) occupy a ver- 

 FIG. 160. tical position upon the upper and posterior 

 part of the cricoid. They are of a triangular 

 shape, and are two in number. They are the 

 smallest in size, and present an anterior sur- 

 face, which is convex and rough, and gives attachment 

 to the chordaz-vocales ; a posterior surface, which is con- 

 cave, for the reception of the arytenoid -muscle ; an inter- 

 nal surface, which is flat, smooth, and covered by mucous 

 membrane, where the two arytenoids approximate ; an 



FIG. 159 represents the Cricoid Cartilage. 



FIG. 160 represents the two Arytenoid Cartilages. 



