THE LARYNX. 355 



a part of the act of deglutition it is carried backward and closes 

 the laryngeal opening. 



The cartilages of the larynx are hyaline, except the cornicula 

 laryngis, cuneiform, and epiglottis, which consist of yellow fibro- 

 cartilage, and, being hyaline, do not become calcined. 



Muscles. Of these there are two sets extrinsic, which arise 

 outside the larynx, and intrinsic, which arise within the larynx 

 and are also inserted within it. 



Extrinsic Muscles. These may be subdivided into the depressors 

 and elevators and exist in pairs. 



The depressor muscles of the larynx and hyoid bone are : Sterno- 

 hyoid, which arises from the clavicle and sternum, and is inserted 

 into the hyoid bone ; sternothyroid, which arises from the sternum 

 and cartilage of the first rib, and is inserted into the ala of the 



FIG. 194. Diagram to illustrate the thyro-arytenoid muscles ; the figure repre- 

 sents a transverse section of the larynx through the bases of the arytenoid carti- 

 lages : Ary, arytenoid cartilage ; p.m, processus muscularis ; p.v, processus vocalis ; 

 Th, thyroid cartilage; c.v, vocal cords; Oe is placed in the esophagus; m.thy.ar.i, 

 internal thyro-arytenoid muscle; m.thy.ar.e, external thyro-arytenoid muscle; 

 m.thy.ar.ep, part of the thyro-ary-epiglottic muscle, cut more or less transversely; 

 m.ar.t, transverse arytenoid muscle (redrawn from Foster). 



thyroid cartilage; thyrohyoid, which appears like a continuation 

 of the sternothyroid, and arises from the side of the thyroid and 

 is inserted into the hyoid bone ; omohyoid, which arises from the 

 upper border of the scapula and is inserted into the hyoid bone. 



The action of this group of muscles is to depress the larynx 

 and hyoid bone at the close of deglutition ; these structures 

 having previously been drawn up with the pharynx. The omo- 

 hyoid by carrying the hyoid backward, as well as depressing it, 

 aids in performing the act of sucking. The thyrohyoid raises the 

 thyroid cartilage as well as depresses the hyoid bone. 



The elevators of the larynx and hyoid bone are the digastric, 

 which arises from the mastoid process of the temporal bone and 

 from near the symphysis of the lower jaw, and is attached to the 

 hyoid bone by a fibrous loop ; stylohyoid, which arises from 

 the styloid process of the temporal bone, and is inserted into 

 the hyoid ; mylohyoid, which arises from the mylohyoid ridge of 



