MUSCLES OF THE LARYNX 317 



Insertion. — Into the front and lower part of the epiglottis. 



Action. — To draw the epiglottis forward and downward after it has 

 been pushed over the glottis in the act of swallowing. 



CricO-Thyroid Muscle. — A small, narrow muscle placed on the outer 

 side of the cricoid cartilage. 



Origin. — From the upper and anterior part of the cricoid cartilage. 



Insertion. — Into the inferior part of the thyroid cartilage. 



Action. — To maintain the two cartilages in position during the action 

 of the more movable parts, while at the same time permitting a certain 

 amount of liberty between themselves. 



Posterior Crico-Arytenoid Muscle. — It occupies the upper and 



back part of the larynx, a great portion of which it covers. It is the 

 largest and most powerful of the intrinsic muscles connected with this 

 organ. 



Origin. — From the posterior broad surface of the cricoid cartilage. 



Insertion. — Into the outer angle of the arytenoid cartilage. 



Action. — To draw the arytenoid cartilages apart and dilate the opening 

 into the larynx. 



Lateral Crico-Arytenoid Muscle. — A small muscle situated on the 



upper and posterior part of the larynx. 



Origin. — From the upper part of the anterior border of the cricoid 

 cartilage. 



Insertion. — Its fibres, passing upwards and backwards, become inserted 

 into the outer angle of the arytenoid cartilage with the posterior crico- 

 arytenoid muscle. 



Acfi(»i. — To constrict the laryngeal opening. 



Thyro-Arytenoid Muscle. — This muscle is composed of two small 

 bundles of fibres situated on the inner side of the thyroid cartilage, where 

 they are separated from each other by the interposition of a pouch of 

 mucous membrane (ventricle of the larynx). 



Origin. — From the inner surface of the body of the thyroid cartilage. 



Insertion. — By some of its fibres into the outer border of the arytenoid 

 cartilage. Others mingle with those of the arytenoid muscle. 



Action. — To constrict the larynx. 



Arytenoideus Muscle. — A pair of small muscles situated on the 

 upper and posterior surface of the arytenoid cartilages. They are united 

 in the middle line by the intermixing of their fibres, and are inserted 

 into the posterior surface of the arytenoid cartilage. 



By some this muscle is said to constrict the laryngeal opening, and by 

 others to dilate or open it. 



