VOCAL AND RESPIRATORY APPARATUS. 249 



The ventricle of the larynx is a deep fossa on either side 

 of the larynx, bounded above by the false vocal cords, below by 

 the inferior or true vocal cords, and externally by the thyro- 

 arytenoideus muscle. 



The sacculus laryngis, or laryngeal pouch, is a membranous 

 sac lined with mucous membrane, opening into the anterior 

 portion of the ventricle of the larynx. Its inner or laryngeal 

 surface is covered by the aryteno-epiglottideus inferior, and the 

 outer side by the thyro-epiglottideus and thyro-arytenoideus 

 muscles. It is compressed by these muscles, discharging its 

 mucous secretion upon the true vocal cords. 



MUSCLES. The intrinsic muscles of the larynx consist of 

 two sets, five connected with the vocal cords and rima glottidis, 

 and three with the epiglottis. The five muscles of the vocal 

 cords are : 



Crico-thyroid. Origin, from the front and sides of the 

 cricoid cartilage; insertion, into anterior border of the inferior 

 cornua, and lower margin of the thyroid cartilage; action. 

 elongates and renders tense the vocal cords; nerve, superior 

 laryngeal. 



Crico-arytcenoideus Posticus. Origin, from the sides and 

 posterior surface of the cricoid cartilage; insertion, into the 

 outer angle of the base of arytenoid cartilage ; action, rotates the 

 arytenoid cartilages outward, opening the glottis, and rendering 

 tense the vocal cords ; nerve, recurrent laryngeal. 



Crico-aryicenoideus Lateralis. Origin, from upper and 

 outer side of the cricoid cartilage; insertion, in front of the 

 preceding into the outer angle of the base arytenoid; action, 

 rotates the arytenoids inward, closing the glottis; nerve, recur- 

 rent laryngeal. 



Arytcunoideus. Origin, from outer border and posterior sur- 

 face of one arytenoid cartilage ; insertion, into the same part of 

 the other its fibres are oblique and transverse; action, by ap- 

 proximating the arytenoids closes the back part of the glottis; 

 nerves, superior and recurrent laryngeal. 



Thyro-arytcenoideus. Origin, from the crico-thyroid mem- 

 brane and lower half of the entering angle of the thyroid car- 

 tilage; insertion, into anterior surface and base of the arytenoid 

 cartilage it consists of inferior and superior portions, the for- 

 mer entering into the formation of the true vocal cords ; action, 

 mainly relaxes the true vocal cords by drawing the arytenoids 

 forward ; nerve, recurrent laryngeal. 



The muscles of the epiglottis are : 



Thyro-epiglottideus. Origin, from the inner surface of thy- 

 roid cartilage; insertion, into the margin of epiglottis and 



