492 



THE HUMAN BODY 



ing the projection known as "Adam's apple." It consists of a 

 framework of cartilages, partly joined by true synovial joints 

 and partly bound together by membranes; muscles are added 



which move the cartilages with 

 reference to one another; and 

 the whole is lined by a mucous 

 membrane. 



The cartilages of the larynx 

 (Fig. 145) are nine in number; 

 three single and median, and 

 three pairs. The largest (t) is 

 called the thyroid, and consists 

 of two halves which meet at an 

 angle in front, but separate be- 

 hind so as to inclose a V-shaped 

 space, in which most of the re- 

 maining cartilages lie. The 

 epiglottis (not represented in the 



FIG. 145. The more important carti- c % - /- i , ,-> c 



lages of the larynx from behind, t, thy- ngure) IS fixed to the topof 



the th id cartilae and 



Ci 



lage;t, arytenoid cartilage ',Pv, the corner hangs the entry from the phar- 

 to which the posterior end of a vocal cord ,11 



is attached; Pm, corner on which the ynx to the larynx; it may be 



muscles which approximate or separate mvprpd bv mil roil s mpm- 



the vocal cords are inserted; co, cartilage S ^ n > covei Dv * 



of Santorini. brane, projecting at the base of 



the tongue, if the latter be pushed down while the mouth is held 

 open in front of a mirror; and is, similarly covered, represented, as 

 seen from behind, at a in Fig. 146. The cricoid, the last of the un- 

 paired cartilages, has the shape of a signet-ring; its broad part 

 (**, Fig. 145) is on the posterior side and lies at the lower part of 

 the opening between the halves of the thyroid; in front and on 

 the sides it is narrow, and a space, occupied by the cricothyroid 

 membrane, intervenes between its upper border and the lower 

 edge of the thyroid cartilage. The angles of the latter are 

 produced above and below into projecting horns (Cs and Ci, 

 Fig. 145), and the lower horn on each side forms a joint with the 

 cricoid. The thyroid can be rotated on an axis, passing through 

 the joints on each side, and rolled down so that its lower front 

 edge shall come nearer the cricoid cartilage, the membrane there 

 intervening being folded. The arytenoids (f, Fig. 145) are the 



