336 



THE RESPIRATORY SYSTEM 



attachment of the vocal fold is carried forwards while the 

 posterior attachment remains fixed, and the folds are there- 

 fore rendered tense. This muscle is extrinsic in position and 

 is supplied by the external laryngeal nerve (p. 97). 



(b) The vocalis and the thyreo-arytsenoid, which really 

 consists of the superficial fibres of the vocalis, pass from the 

 thyreoid cartilage in front to the lateral surface of the 



FIG. 119. The Interior of the Left Half of the Larynx. The 

 mucous membrane and the laryngeal muscles have been removed. 

 (TURNER'S Anatomy.} 



A. Arytaenoid cartilage. 

 C, Cricoid cartilage. 

 T. Thyreoid cartilage. 

 V. Laryngeal ventricle. 

 a. Vocal process of arytaenoid car- 

 tilage. 

 f* Ventricular fold (false vocal cord). 



ic. Inferior cornu of thyreoid cartilage. 

 let. Conus elasticus (crico-thyreoid 



membrane). 

 r. Thyreoid angle. 

 sc. Superior cornu of thyreoid car- 

 tilage. 

 t. Vocal fold (true vocal cord). 



arytsenoid behind. Their contraction approximates the two 

 attachments of the vocal folds, which consequently become 

 relaxed. 



(c) The crico-arytsenoideus posterior arises from the 

 posterior surface of the cricoid, below, and is inserted into the 

 muscular process (lateral basal angle) of the arytaenoid. Its 

 line of pull lies posterior to the centre of the crico-arytaenoid 

 joint, and its contraction, therefore, rotates the arytaenoid so 



