LAKYNGEAL MUSCLES. 



1075 



which lie in the side walls of the 

 thyreo - arytsenoideus, medially by 

 appendix ventriculi laryngis, and later- 

 ally by the lamina of the thyreoid car- 

 tilage. It constitutes what was formerly 

 described as the uppermost fibres of the 

 thyreo-arytsenoideus externus muscle. 



Each thyreo -epiglotticus arises from 

 the medial surface of the lamina of the 

 thyreoid cartilage, immediately above 

 the origin of the thyreo - aryteenoideus. 

 From this origin the fibres run in arches, 

 upwards and dorsally, to be inserted 

 partly into the margin of the ary- 

 epiglottic fold, and partly into the lateral 

 margin of the epiglottis, being inter- 

 mingled with the fibres of the ary- 

 epiglotticus. 



By its action the^thyreo-epiglotticus 

 widens the aditus and the vestibulum 

 laryngis. Its innervation is derived 

 from the ventral ramus of the inferior 

 laryngeal nerve. 



The mm. cricothyreoidei are a pair 

 of quadrangular muscles, broader and 



larynx. Each is bounded below by 

 the thyreo - epiglottic ligament and 



the 

 the 



Epiglottis 



Cartilage 

 _________ -triticea 



Lesser cornu 

 -of hyoid 

 -Greater cornu 



of hyoid 



Body of hyoid 



Thyreo- 

 ----. epiglottic 

 ligament 



Bpiglott 



t surface of 

 >11 of vestibule 

 of larynx" 



Epiglottic 

 tubercle 'V 



Ventricular fold--W~ 

 Ventricle of \ 



larynx 

 Vocal fold -' 

 M. vocal 

 M. thyreo-.. 

 arytsenoideus 



id cartilage 



"-----Ring of trachea 



of trachea -- 



. 856. FRONTAL SECTION OF THE LARYNX 

 SHOWING MUSCLES. 



tilage; and (2) a pars obliqua 

 the inferior cornu. The muscle 



FIG. 855. THE CRICO-THYREOID MUSCLE OF THE 

 RIGHT SIDE. 



thicker above than below. They lie 

 on the cricoid cartilage and bridge 

 over the crico-thyreoid interval, and 

 are, therefore, the only intrinsic 

 laryngeal muscles which are visible 

 in an ordinary dissection of the neck. 

 Each is covered laterally and in part 

 by the thyreoid gland and the sterno- 

 thyreoid and the sterno-hyoid mus- 

 cles. Between the two muscles of 

 opposite sides there is an inter^ 

 mediate triangular area left in which 

 the crico-thyreoid ligament is visible. 

 Each crico - thyreoideus arises 

 from the lower border and lateral 

 surface of the arch of the cricoid 

 cartilage, and from this origin its 

 fibres radiate dorsally and upwards 

 to be inserted into the inferior border 

 and medial surface of the lamina of 

 the thyreoid cartilage, as far as its 

 inferior cornu, and also into the in- 

 ferior cornu itself. As a general 

 rule each muscle is divided into two 

 parts, viz., (1) a pars recta composed 

 of those fibres which are inserted 

 into the lamina of the thyreoid car- 

 formed of those fibres which are inserted into 

 is closely associated with the inferior constrictor 



