358 



RESPIRATION. 



14 



larynx and other anatomic structures, in considering the action of 

 these muscles, says that they may be conveniently divided into 

 two groups, viz., 1. Those which open and close the glottis; 2. 

 Those which regulate the degree of tension of the vocal cords. 



1 . The muscles which open the glottis are the crico-ary tenoidei 

 postici, and those which close it are the arytenoideus and the crico- 



arytenoidei laterales. 2. The 

 muscles which regulate the 

 tension of the vocal cords are 

 the crico-thyroidei, which tense 

 and elongate them ; and the 

 thyro-arytenoidei, which relax 

 and shorten them. The thyro- 

 epiglottideus is a depressor of 

 the epiglottis, and the aryteno- 

 epiglottidei constrict the supe- 

 rior aperture of the larynx, 

 compress the sacculi laryngis, 

 and empty them of their con- 

 tents. 



Interior. If the larynx is 

 inspected from above, looking 

 downward (Fig. 196), it will be 

 seen that its opening is bounded 

 in front by the epiglottis, behind 

 by the inter arytenoid fold, con- 

 sisting of mucous membrane, 

 connecting the arytenoid carti- 

 lages, and the aryteno-epiglottic 

 folds, also mucous membrane, 

 which connect the sides of the 

 epiglottis and the arytenoid car- 

 tilages. The cartilages of San- 

 torini and Wrisberg make prom- 

 inences in these folds. 



The cavity of the larynx 

 (Fig. 197) extends from its 

 opening to the lower border of 

 the cricoid cartilage. In look- 

 ing into it there will be seen 

 the inferior or true vocal cords, 



vocal bands or ligaments, the portions which approximate the most 

 closely, and between them a space or fissure, the glottis or rima glot- 

 tidis. The term rima glottidis is applied by some authors to the 

 boundary of the space, and by others to the space itself, using it 

 synonymously with glottis. Above the true vocal cords are the 

 superior or false vocal cords, and between the true and false on 



FIG. 197. Vertical transverse section 

 of the larynx : 1, posterior face of epiglot- 

 tis, with 1', its cushion ; 2, aryteno-epi- 



fossa of Merkel; 6, ventricle of larynx, 

 with 6', its ascending pouch; 7, anterior 

 portion of cricoid ; 8, section of cricoid ; 

 9, thyroid, cut surface ; 10, thyrohyoid 

 membrane; 11, thyrohyoid muscle; 12, 

 aryteno-epiglottic muscle ; 43, thyro-ary- 

 tenoid muscle, with 13', its inner division, 

 contained in the vocal cord ; 14, cricothy- 

 roid muscle; 15, subglottic portion of 

 larynx ; 16, cavity of the trachea (after 

 Testut). 



