

LAKYNGEAL MUSCLES. 



1073 



Epiglotti 



Lesser cornu of. 

 hyoid 



Body of hyoid- 



Hyo-epiglottic 

 ligament 



Lamina of 

 thyreoid cartilage" 



M. thy 



arytsenoideus - 

 M. crico-ary- 

 tteuoideus lateralis" 



M. crico- 

 ary titmoideus" ~ " 



posterior 

 Con us elasticus: 



--M. ary-epiglotticu 



M. thyreo- 



epiglotticus 



Corniculate 

 cartilage 



Muscular pro- 

 cess of aryta;- 

 noid cartilage 



From this origin the nmscular fibres run dorsally and upwards, and converge to 



be inserted into the ventral surface of the processus muscularis of the arytsenoid 



cartilage. The muscle is not infre- 

 quently inseparable from the (external) 



thyreo-arytaenoid muscle. 



By its action the lateral crico-ary- 



tsenoid muscle draws the processus 



muscularis of the arytsenoid cartilage 



ventrally and downwards, thus turning 



the processus vocalis of the same car- 

 tilage medially, and tending thereby to 



stretch the vocal fold and to approxi- 

 mate it to its fellow of the opposite side, 



thus assisting in closure of the rima 



glottidis. Its nerve supply is the 



anterior ventral branch of the inferior 



laryngeal nerve. 



The Mm. Thyreoarytaenoidei (O.T. 



Thyreoarytaenoideus Externus). 



Each thyreo - arytsenoid muscle is a 



thin, quadrangular muscle, which is only 



separable from the corresponding in. 



vocalis, with which it forms a common 



mass, by artificial means. 



It lies in the lateral wall of the 



larynx, immediately to the medial side 



of the lamina of the thyreoid cartilage, 



and lateral to the appendix ventriculi 



laryngis, the m. vocalis, and the conus Fm 853 ._. Dl88KCTION OF THE MUSCLES OP THE- 



elasticus ; its inferior border is in con- SIDE WALL OF THE LARYNX. 



tact with the lateral crico-arytaenoid 



muscle, whilst its superior border ex- 

 tends farther upwards than the vocal 

 fold, and is in contact with the inferior 

 border of the thyreo-epiglotticus. 



It arises from the inferior half of 

 the medial surface of the lamina of the 

 thyreoid cartilage, close to its ventral 

 angle, and also from the lateral part of 

 the conus elasticus. The muscular fibre's 

 pass dorsally and upwards to be inserted 

 into the lateral border and muscular 

 process of the ary taenoid cartilage ; some 

 of the fibres, however, turn round this 

 cartilage and become continuous with 

 thearytaenoideus transversus. The upper 

 fibres of the thyreo-arytsenoideus vary 

 very greatly in their development and 

 arrangement. 



By its action the muscle rotates the 

 arytsenoid cartilage and draws it ven- 

 trally in such a way that its vocal pro- 

 cess is carried ventrally and medially and 

 the vocal fold is rendered somewhat 

 flaccid. The muscle thus antagonises 

 the crico-thyreoideus. The main action 

 of the muscle must, however, be that of 

 a constrictor of the supraglottic region 

 of the larynx. 



69 



. 854. DISSECTION OF THE MUSCLES ON THE 

 DORSAL ASPECT OF THE LARYNX. 



