LARYNGEAL MUSCLES. 



333 



THYRO-ARYTENOIDEUS. 

 (Fig. 116. d.) 



Situated on the inner side of the wing of the thyroid cartilage, 

 it consists of two bundles, separated by the ventricle of the 

 glottis. 



Origin. — From the inner surface of the angle of the thyroid 

 cartilage, outside of the vocal cord. 



Insertion. — To the middle line at the 

 junction of the arytenoid cartilages. 



Action. — To constrict the glottis. By 

 its relation with the vocal cord this muscle 

 powerfully influences the tension of the 

 same, and consequently the voice. 



ARYTENOIDEUS. 



(Fig. 116. a.) 



This muscle, the smallest of the group, is 

 single, and situated upon the arj^tenoid 

 cartilages, stretching from one cartilage to 

 the other, the fibres intercrossing in the 

 median line. 



Action. — To approximate the cartilages, 

 and thus constrict the glottis. 



The mucous membrane is continuous with 

 that of the tongue and pharynx, forming, 

 from the tongue to the epiglottis, the glosso- 

 epiglottidean folds. It is reflected over the 

 posterior face of the epiglottis to the anterior 

 part of the arytenoids, covering the lateral 

 Iboundary of the laryngeal opening. In 

 these folds lie the cuneiform cartilages. It 

 thus passes over the false vocal cords, lining the ventricles, and 

 returning over the true vocal cords ; it clothes the inner surface 

 of the cricoid cartilage and middle of the crico-thyroid ligament, 

 and so is prolonged into the trachea. It is very thin, and exqui- 

 sitely sensitive, especially about the glottis ; it is covered with 

 ciliated epithelium, and studded with mucous glands, which 

 moisten it and preserve its sensitiveness. The glands are 



Fig. 116. 



Muscles of the larynx — 

 left lateral view— the thyiDid 

 wing being removed. a, 

 Arytenoideus ; 6, Crico-ary- 

 tenoideus posticus ; c, Crico- 

 arytenoideus lateralis ; d. 

 Thyro-arytenoideus. 



