454 



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AI-I-AKATIS i\ M \.MMMJ.I. 



Fig. 229. 



I-OSTKRO-LATKRAI, VIKW OK Till: 

 I.AKVNX. 



7, Crico-arytcnoideus posticus ; 8, 



Tho crico-thyroidcus shortens tho larynx, iu bringing together the two 

 mrti?:iirrs into whicli it is inserted. 



POSTERIOB CBICO-AKYTENOIDECB (Fig. 

 229, 7) This is tho most powerful muscle 

 in this region. Its fibres are directed for- 

 wards and outwards, and originate from 

 tho bezel of tho cricoid, whicli they rover, 

 and from the median crest of that part. 

 They all converge, in becoming more or l-ss 

 tendinous, towards tho posterior tulwrclo of 

 tho arytciioid cartilage, on which they ter- 

 minate. Covered by the oesophagus and 

 the crico-pharyngeal muscular band, this 

 muscle is separated from that of the oppo- 

 site side by the median crest of the cricoid 

 bezel. 



The posterior cricc-arytenoid muscles 

 dilate the entrance to the larynx, as well as 

 the glottis, in causing the arytenoid car- 

 tilages to rotate or swing on tho cricoid 

 cartilage, and iu separating them from our. 

 another by their anterior and inferior bor- 

 ; 2, Arytenoid cartilages ; dors. They act as a lever of the first order. 



3, hyroid wrUbMi 4, Arytenoi- LATERAL ( 5RICO-ARYTENOIDEU8 (Fig. 229, 



-A tnug.br muscle, smaller ,, 

 preceding, situated between the thyroid 



Crico-thyroiduus ; 9, Ligament be- and arytenoid cartilages, and formed of 

 twecu the cricoid cartilage and fasciculi longer in front than behind ; these 



lirst rin f g ? ( trachea, 10; 11, In- or i g i nato on tho s iJ c o f tho antc rior border 

 fero-posterior extremities of crico- ., , . , ... ,. 



thvroid cartilages. * * ne cncoid cartilage, and are directed 



upwards to terminate outside the posterior 

 crico-arytenoideus, on the tubercle of the arytenoid cartilage. 



It is a direct antagonist of the last muscle, and, consequently, a con- 

 strictor of the larynx. 



THYBO ARYTENOIDEUS (Fig. 229, 6). Lodged at the inner face of tho 

 thyroid ala, this muscle comprises two fasciculi, separated by the ventricle 

 of the glottis. 



The anterior fasciculus is a long and pale band, originating on tho 

 Mill-null surface of the ala of the thyroid cartilage, near its receding single, 

 and ascending to the arytenoid cartilage, bending round its external face to 

 join, on tho median line, the analogous fasciculus from the opposite side, 

 mixing its fibres with those of tho arytenoideus. By its inner face it covers 

 the superior vocal cord and the laryngeal mucous membrane. 



The posterior fasciculus, wider than tho anterior, comports itself in a 

 somewhat similar manner. It commences from behind the same point, and 

 terminates on tho external crest of tho arytenoid cartilage ; but its most 

 anterior fibres pass over this crest and join the arytenoid muscle. Its 

 internal face corresponds to the vocal cord, and its posterior border is con- 

 founded with the fibres of the lateral crico-arytenoidcus. 



Sometimes it happens that these fasciculi are not distinct from each 

 other, and exist only as a wide muscular band applied against the ventricle 

 of the glottis. 



It is surmised that this muscle is a constrictor of tho larynx. 1 







