490 



MOVEMENTS VOICE AND SPEECH. 



to be inserted into the outer angle of the inferior portion of the arytenoid 

 cartilages, rotate these cartilages outward, separate them, and act as dilators of 



the chink of the glottis. These muscles are 

 chiefly concerned in the respiratory move- 

 ments during inspiration. 



The muscles mainly concerned in the 

 modifications of the voice by their action 

 upon the vocal chords, are the crico-thyroids, 

 the arytenoid, the lateral crico-arytenoids and 

 the thyro - arytenoids. The following is a 

 sketch of their attachments and mode of ac- 

 tion: 



Crico-tJiyroid Muscles. These muscles 

 are situated on the outside of the larynx, at 

 the anterior and lateral portions of the cri- 

 coid cartilage. Each muscle is of a triangu- 

 lar form, the base of the triangle presenting 

 posteriorly. It arises from the anterior and 

 lateral portions of the cricoid cartilage, and 

 its fibres diverge to be inserted into the in- 

 FIG. 168. Lateral mew of the muscles of ferior border of the thyroid cartilage, extend- 



the larynx (Sappey). . , . 1 AV v _J^ 



i, body of the hyoid bone ; a, vertical m g * m tn e middle of this border posterior- 



section of the thyroid cartilage; 3, i f ha ok fl<? thp inf prior pnrrma T on 



horizontal section of the thyroid car- lv > db Idr UdLK dS Ilia. .L.OD 



tilage, turned downward to show the ~ p 4. a ff pr Hiviflina f VIP nprvmiss filflmpnf rlia 



deep attachment of the crico-thy- & et ' am dividing me nerVOUS niamei 



ti-ihiiiprl in tVipp mnplp nnfpH ft pprfnin HP 

 1 ' leb > n 



g ree of hoarseness of the voice due to relaxa- 



tion of the vocal chords ; and b y imitating 

 their action mechanically, he approximated 

 the cricoid and thyroid cartilages in front, 

 carried back the arytenoid cartilages and ren- 

 dered the chords tense. 

 Arytenoid Muscle. This single muscle fills up the space between the two 

 arytenoid cartilages and is attached to their posterior surface and borders. 

 Its action evidently is to approximate the posterior extremities of the chords 

 a-nd to constrict the glottis, as far as the articulations of the arytenoid carti- 

 lage with the cricoid will permit. In any event, this muscle is important in 

 phonation, as it serves to fix the posterior attachments of the vocal chords 

 and to increase the efficiency of certain of the other intrinsic muscles. 



Lateral Crico-arytenoid Muscles. These muscles are situated in the in- 

 terior of the larynx. They arise from the sides and superior borders of the 

 cricoid cartilage, pass upward and backward, and are attached to the base of 

 the arytenoid cartilages. By dividing all the filaments of the recurrent laryn- 

 geal nerves, except those distributed to these muscles, and then stimulating 

 the nerves, Longet has shown that they act to approximate the vocal chords, 

 and that they constrict the glottis, particularly in its interligamentous por- 

 tion. These muscles, with the arytenoid, act as constrictors of the larynx. 



roid muscle ; 4, facet of articulation 

 of the small cornu of the thyroid car- 



enoid muscle ; 8, lateral crico-aryte- 

 noid muscle ; 9, thyro - arytenoid 

 muscle ; 10, arytenoid muscle ; 11, 

 ary teno - epiglottidean muscle ; 12, 

 middle thyro -hyoid ligament ; 13, 

 lateral thyro-hyoid- ligament. 



