THE HEAD AND NECK, POSTERIOR. 147 



Lateral Cricoarytenoid. 



From the lateral upper border of the cricoid cartilage, 

 into the muscular process of the arytenoid cartilage. The 

 action is to approximate the vocal cords by drawing the 

 arytenoid cartilages together. 



Thyro -arytenoid. 



By a vertical origin from the inner surface of the thy- 

 roid cartilage near the median line. It is attached pos- 

 teriorly into the base and side of the arytenoid cartilage. 

 The muscle consists of two portions, an upper and a lower. 

 The lower portion lies parallel with the true vocal cord 

 and some of its fibres pass into it. 



ACTION OF THE MUSCLES MOVING THE VOCAL CORDS. 



(From Ho I den?} 



Cricothyroidei, To stretch the vocal cords. 



Thyro-arytenoidei, To relax the vocal cords and place 



them in the vocalizing position. 



Crico-arytenoidei postici, . . . Dilate the glottis. 



Crico-arytenoidei laterales, . . Draw together the arytenoid carti- 

 lages. 



Arytenoideus, Draw together the arytenoid carti- 

 lages. 



Aryteno-epiglottidei, Contract the upper opening of the 



larynx. 



Nerve Supply for the Muscles of the Larynx. 



The external branch of the superior laryngeal supplies 

 the cricothyroid. The inferior laryngeal nerve supplies all 

 the remaining muscles of the larynx. 



The muscles connecting the epiglottis with the thyroid 

 cartilage (thyro-epiglottideus, with the aryteno-epiglot- 

 tideus superior and inferior) are thin bands of muscular 

 fibres which need not detain the general dissector. 



