542 



VOICE AND SPEECH 



n 



The larynx as a whole, as well as the trachea, is movable, because 

 it is suspended from the hyoid bone by the thyrohyoid muscles. This 

 bone in turn is affixed to the base of the skull and the maxillae 

 by a number of muscles, and is therefore also freely movable. The 

 upward movement of the larynx is counteracted by the sternothy- 

 rohyoid muscles which unite this organ with the sternum. The 



larynx may be displaced for a dis- 

 tance of several centimeters, first 

 in consequence of the muscular 

 activity coincident with the act of 

 swallowing and secondly, in con- 

 sequence of the adjustment of the 

 laryngeal parts for purposes of 

 phonation. In the former case, the 

 larynx is also tilted forward, in- 

 suring a greater prominence of its 

 anterior border. 



In longitudinal section the 

 laryngeal cavity exhibits the shape 

 of an hour-glass, the true vocal 

 cords forming the line of demarca- 

 tion between its upper and lower 

 recesses. Moreover, while the long 

 axis of its upper recess is directed 

 strongly backward, that of the lower 

 conforms more closely to the general 

 course of the trachea. The thyroid 

 cartilage forms the front and sides 

 of the upper part of the larynx. 

 It is composed of two nearly square 

 plates which are placed vertically 

 and are united in front by a bridge 

 which gives rise to a prominence, 

 known as the pomum Adami. 

 Posteriorly, they are rather widely 

 separated from one another, the in- 

 tervening space being filled by soft 

 tissues. The cricoid cartilage forms 

 a heavy ring which completely sur- 

 rounds the lower cavity of the 

 larynx. It is narrow in front, but 



broadens out posteriorly into a quadrate plate. The latter is narrowed 

 above into a pointed process. The arylenoid cartilages are two ir- 

 regular, triangular plates, the bases of which are placed transversely 

 upon the superior processes of the cricoid. The corniculce laryngis are 

 two small cone-shaped cartilages which are fastened to the upper pro- 



FIG. 268. VERTICAL TRANSVERSE 

 SECTION OF THE LARYNX. (After Testut.) 



1, posterior face of epiglottis, with 1', 

 its cushion; 2, aryteno-epiglottic fold; 3, 

 ventricular band, or false vocal cord; 4, 

 true vocal cord; 5, central fossa of 

 Merkel; 6, ventricle of larynx, with 6', 

 its ascending pouch; 7, anterior portion 

 of cricoid; 8, section of cricoid; 9, thy- 

 roid, cut surface; 10, thyrohyoid mem- 

 brane ; 11, thyrohyoid muscle; 12, 

 aryteno-epiglottic muscle; 13, thyro- 

 arytenoid muscle, with 13', its inner 

 division, contained in the vocal cord; 14, 

 crico thyroid muscle; 15, subglottic por- 

 tion of larynx; 16, cavity of the trachea. 

 (American Text-book of Physiology.) 



