540 



HANDBOOK OF PHYSIOLOGY. 



GROUP. 



MUSCLE. 



ATTACHMENTS. 



ACTION. 



II. and III. (b) Middle A single muscle. Half-q u a d r i- jDraws together the 

 Adductors layer. lateral, attached to the borders arytenoid carti- 



and i. Aryte- of the arytenoid cartilages, its lages and also de- 



Sphincters, n o i d e us fibres running horizontally be- presses them. 

 continued, posticus. tween the two. When the mus- 



cle is paralyzed, 

 the inter- carti- 

 laginous part of 

 the cords cannot 

 come together. 



11. Thyro- A pair of muscles. Each of which 

 aryteno i - consists of three chief portions 

 d e i ex- lower, middle, and upper 

 terni. The lower and principal fibres 



may be further divided into two 

 layers, internal and external. ! 

 These fibres arise side by side 

 from the lower half of the inter- 

 nal surface of the thyroid carti- 

 lage, close to the angle, and from 

 the fibrous expansion of the crico-i 

 thyroid ligament, and are insert-; 

 ed into the lateral border of the' 

 arytenoid cartilage. The inner! 

 fibres run horizontally, to be at- 

 tached to the lower half of this 

 border, and the outer fibres pass 

 obliquely outward to be inserted 

 into the upper half, while some 

 pass to the cartilage of Wrisburg 

 and the ary-epiglottic fold. 



iii. Crico- A pair of muscles. They arise on 



aryteno i 

 dei later- 

 ales. 



(c) Inner- 

 most lay 

 er, Thyro- 

 arytenoi- 

 dei in - 

 terni. 



eithar side from the middle third 

 of the upper border of the cricoidj 

 cartilage and are inserted into the' 

 whole anterior margin of the base 

 of the arytenoid cartilage. Some| 

 of their fibres join the thyroid- 1 

 ary-epiglottici. 



Approximate the 

 vocal cords 

 by drawing the 

 processus mus- 

 cularis of the 

 arytenoid carti- 

 lages forward 

 and downward 

 and so rotate the 

 processus vocalis 

 inward. 



A pair of muscles. They arise on Render the vocal 



either side, internally from the; 

 angle of the thyroid cartilage,! 

 internal to the last described 

 muscle ( (b), iii.), and running 

 parallel to and in the substance of 

 the vocal cords are attached pos- 

 teriorly to the processus vocalis 

 along their whole length and to 

 the adjacent part of the outer 

 surface of the arytenoid carti- 

 lages. 



cords tense and 

 rotate the aryte- 

 noid cartilages 

 and approximate 

 the processus 

 vocalis. 



