Co-rnn aupfr. 



45 



377* Larynx after Removal of the Left Thyroid 



Lamella, lateral view. 

 The muscles of the larynx (all in pairs) are: 



1. At the external portion of the larynx: 



a) M. crico-thyroickus (see Fig. 373) arises from the front and lateral 

 part of the cricoid cartilage and running obliquely upwards, is inserted into 

 the lower border of the thyroid cartilage. Produces tension of the vocal cords. 



b) M. crico-arytaenoideus posticus arises from a depression on the 

 corresponding half of the posterior surface of the cricoid cartilage, and 

 passing outwards and upwards, is inserted into the muscular process of 

 the arytenoid cartilage. Rotates this cartilage and opens the glottis. 



c) M. crico-arytaenoideus lateralis arises from the upper border of 

 the side of the cricoid cartilage, covered by the lamella of the thyroid 

 cartilage; passing obliquely backwards and upwards, it is inserted into 

 the muscular process. Antagonist of the former. 



d) MM. arytaenoidei transversi et oibliqui (see Fig. 378) pass trans- 

 versely and obliquely, from one arytenoid cartilage to the other, being 

 inserted into its posterior concave surface. Approximate the vocal cords 

 and narrow the opening of the glottis. 



2. At the inner surface of the larynx : 



a) M. thyro-arytaenoideus lies parallel with the outer side of the true 

 vocal cord; it arises from the inner surface of the thyroid cartilage, and is 

 inserted into the vocal process and anterior border of the arytenoid carti- 

 lage. Narrows the glottis. 



b)-M tliyreo-epiylotticus and M. ary-epiglotticus between the layers of iheLig. 

 ary-epiylotticum,passii[\gfi'om. the thyroid and arytenoid cartilages to the epiglottis. 



