CH. LIV.J 



MUSCLES OF LARYNX. 



731 



Lag. ary-epiglott. . 



Cart. Wrisbergii 



mm. Aryten. obliqu. ..-.* 



in the false vocal cord. The portion of this muscle which extends towards 

 the epiglottis is often described as a separate muscle (thyro-rpi<jh>tt'n1i-un')\ 

 it resembles the crico-arytenoid in that some of its fibres are continuous with 

 those of the arytenoid muscle. 



The antero-posterior fibres will tend to draw forward the arytenoid carti- 

 lage, and with it the posterior part of the cricoid cartilage, rotating the 

 latter upwards and antagonizing the action of the crico-thyroid muscle, the 

 effect being to relax the vocal cords. But if the latter are kept stretched 

 those fibres of the inner portion of the muscle which are inserted into the 

 vocal cord may serve to modify its elasticity, tightening the parts of the cord 

 in front of, and relaxing those behind, its attachment. The vertical fibres of 

 the muscle which extend from the crico-thyroid membrane across the base 

 of the vocal fold and over the ventricle into the false vocal cord, render the 

 free edge of the former more prominent. Then the fibres which are inserted 

 into the muscular process and outer surface of the arytenoid cartilage will 

 tend to draw the aryte- 

 noid cartilage forwards 

 and rotate it inwards ; 

 finally, the fibres which 

 pass into the aryteno- 

 epiglottidean fold may 

 assist in depressing the 

 epiglottis. 



If these muscles are 

 paralysed, the lips of 



the glottis are no longer Cart - Santorini 



parallel, but are curved 

 with the concavity in- 

 wards, and a much 

 stronger blast of air is 

 required for the pro- 

 duction of the voice. 



5. Ar i/t e n it id. 

 When Uie mucous 

 membrane is removed 

 from the back of the 

 arytenoid cartilages, a 

 band of transverse 

 fibres is exposed, on 

 the dorsal surface of 

 which are two slender 

 decussating oblique 

 bundles. These are 

 often described as 



separate muscles (arytenoid and aryteno-epiglottidean), but they are inti- 

 mately blended together. The ventral fibres (arytenoid proper) pass straight 

 across from the outer half of the concave surface on the back of one 

 arytenoid cartilage to the corresponding surface of the other. The dorsal 

 fibres can be followed to the lateral walls of the larynx, the uppermost ones 

 to the cartilage of Santorini, the intermediate ones run with the uppermost 

 fibres of the thyro-arytenoid muscle forming the so-called aryteno-epi- 

 glottidean muscle, and the lowest fibres blend at the level of the true vocal 

 cords with the thyro-arytenoid and lateral crico-arytenoid muscles. 



The arytenoid muscle draws the arytenoid cartilages together. If it 

 i> panily-cd, the intercartiliiginous part of the glottis remains open, although 

 the membranous lips can still be approximated during vocalisation. 



It has been generally supjwsed that the epiglottis is depressed as a lid 

 over the glottis during swallowing. This may be so in some animals, but in 

 man it is not the case ; the epiglottis projects upwards in close contact with 



Crico-arytenoid. post *J 



Comu inferior 



Lag. cerato-cric. 



Pars post. inf. membrani 

 Pars cartilag. 



Fig. 553. The larynx as seen from behind. To show the 

 intrinsic muscles posteriorly. (Stoerk.) 



