4:90 



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-thyroid 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- 

 FIO. 168. Lateral view of the muscles of ferior border of the thyroid cartilage, extend- 



the larynx (Sappey). . J . c 



i, body of the hyoid bone ; 2, vertical m g rom the middle of this border postenor- 



, as far back as the inferior cornua. Lon- 



roid muscle ; 4, facet of articulation 

 of the small cornu of the thyroid car- 

 tilage with the cricoid cartilage ; 5, 

 facet on the cricoid cartilage ; 6, su- 

 perior attachment of the crico-thy- 

 roid muscle ; 7, posterior crico-aryt- 

 enoid muscle ; 8, lateral crico-aryte- 

 noid muscle ; 9, thyro - arytenoid 

 muscle ; 10, arytenoid muscle ; 11, 

 aryteno - epiglottidean muscle ; 12, 

 middle thyro - hyoid ligament ; 13, 

 lateral thyro-hyoid ligament. 



get, after dividing the nervous filaments dis- 

 tributed to these muscles, noted a certain de- 

 gree of hoarseness of the voice due to relaxa- 

 tion of the vocal chords; and by 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 

 and 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. 



