THE LARYNX. 



169 



Crico-arytenoideus Lateralis d (2), from the FIG. 83. 



upper lateral border of the cricoid cartilage, 

 into the posterior angle of the base of the 

 arytenoid. Action, to rotate the arytenoids 

 inwards and close the glottis. Nerve, recur- 

 rent laryngeal. 



Thyro-arytenoideus e (2), from the angle of 

 the thyroid cartilage and the posterior surface 

 of the crico -thyroid membrane, into the 

 base and anterior surface of the arytenoid. 

 Action, to shorten and relax the vocal chords 

 by approximating the cartilages, and to com- 

 press the sacculus laryngis. Nerve, recurrent 

 laryngeal. 



Arytenoideus (i), from the posterior surface 



and outer border of one arytenoid cartilage, into the corresponding parts 

 of the opposite cartilage; having oblique and transverse fibres, and filling 

 up the posterior concave surfaces of the arytenoid cartilages. Action, by 

 approximating the arytenoids, to close the back part of the glottis. 

 Nerves, superior and recurrent laryngeal. 



A small fasciculus, called the Kerato-cricoideus, is sometimes found below 

 the arytenoideus, extending from the cricoid cartilage to the inferior cornu 

 of the thyroid. It occurs once in 5 cases, usually on one side only, but 

 occasionally on both, and acts to fix the lower horn of the thyroid carti- 

 lage backwards and downwards. 



Another small muscle is found frequently, though rarely described in the 

 books, the Triticeo-glossus. It arises from the cartilaginous nodule in the 

 lateral thyro-hyoid ligament, and passes forwards and upwards to enter 

 the tongue along with the kerato-glossus muscle. 



Describe the Muscles of the Epiglottis. They are 3 double muscles, 

 as follows, viz. 



Thyro-epiglottideus (2), from the inner surface of the thyroid cartilage, 

 into the margin of the epiglottis, and the aryteno-epiglottidean fold. 

 Action, to depress the epiglottis, and compress the sacculus laryngis. 

 Nerve, recurrent laryngeal. 



Aryteno-epiglottideus Superior (2), from the apex of the arytenoid carti- 

 lage, into the aryteno-epiglottidean fold. Action, to constrict the supe- 

 rior aperture of the larynx. Nerve, recurrent laryngeal. 



Aryteno-epiglottideus Inferior (2), from the arytenoid cartilage just above 

 the attachment of the superior vocal chord, into the sacculus laryngis 



