MUSCLES OF THE LARYXX. 



2'n 



brane, and is inserted into the anterior projection on the base of the 

 arytenoid cartilage and to the surface adjacent, close to the insertion of 

 the lateral crico-arytenoid. The upper i\\h\ portion of the thyro-arytenoid 

 muscle is inserted higher up on the anterior surflicc and outer border 

 of the arytenoid cartilage. 



The lower portion of the muscle contributes to the support of the 

 true vocal cord lying parallel with it ; into the outer surface of the 

 ligament some of its fibres are inserted. The upper thin portion, 

 external to the lower, lies upon the laryngeal pouch and ventricle, close 

 Jjeneath the mucous membrane : indeed the entire muscle may be 

 exposed from the interior of the larynx, by raising the mucous mem- 

 brane of the sinus and vocal cord. Fibres from this muscle pass 

 round the border of the arytenoid cartilage, and become continuous 

 with some of the oblique fibres of the arytenoid muscle, to be presently 

 described. 



Santorini descriljcd three thyro" '°' '^' 



aryiienoicl muscles, an hifcrUir and a 

 middle, which are constant, and a 

 .siipci'ior, which is sometimes present. 

 The fibres of the superior fasciculus (fig. 

 1 '.).■). cZ'), when present, arise nearest to 

 the notch of the thyroid cartilage, and 

 are attached to the upper part of the 

 base of the arytenoid cartilage. This is 

 named by Soemmerring the ■■^■ina/l thyro- 

 iirjiienoid, whilst the two other portions 

 of the muscle constitute the r/rcat 

 thjTo-ar^-tenoid of that author. 



Arytenoid and aryteno - 

 epiglottidean muscles. — When 

 the mucous membrane is removed 

 from the back of the arytenoid 

 cartilages, a thick band of trans- 

 verse fibres constituting the aryte- 

 noid muscle is laid bare (fig. 194, a), 

 and on the surface of this are 

 seen two slender decussating ob- 

 lique bundles (s), formerly de- 

 scribed as portions of the arytenoid 

 muscle (arytfenoideus obliquus), 

 but now more generally con- 

 sidered as parts of the aryteno- 

 cpiglottidean muscles, with which 

 they are more closely associated 

 both in the disposition of their 

 fibres and in their action. The - 

 aryiciioid muscle passes straight 

 across, and its fibres are attached 

 to the whole extent of the con- 

 cave surface on the back of each 

 arytenoid cartilage. The aryteno- 

 epifiMtidean muscles (fig. 19G h) arising near the inferior and outer 

 angles of the arytenoid cartilages, decussate one with the other, and 



Fig. 196. — View of the Interior op 

 THE Left Half op the Larvnx (after 



Hilton.) 



a, left arytenoid cartilage ; c, e, divided 

 surfaces of the cricoid cartilage ; t, thyroid 

 cartilage ; c, epiglottis ; v, left ventricle 

 of the larynx ; }•, left inferior or true 

 vocal cord ; s, placed on the inner wall of 

 the laryngeal pouch ; h, aryteno-epiglot- 

 tideaa muscle ; /, interior of the trachea. 



