HEAD. 99 



superior vocal cords ; 8 — the cricoid cartilages to the 

 tracliea by the crico-tracheal elastic membrane. 



Muscles. — Three extrinsic : 1 — Sterno-thyroideus 

 (see inferior cervical region) ; 2 — Hyo-tliyroidens. 

 Attachments : "Whole extent of the hyoid cornu, exter- 

 nal face of the thyroid cartilages. Action : Carries 

 the larynx forward and upward ; 3 — Hyo-epiglottideus. 

 Attachments : Superior face of the body of the hyoid 

 bone, and antero-inferior face of the epiglottic cartil- 

 ages. Action : Pulls the epiglottic cartilage to normal 

 position. Five intrinsic : 1. — Crico-thyroideus. At- 

 tachments : from the cricoid to the posterior border of 

 the thyroid, it shortens the larynx ; 2. — Posterior cri- 

 co-arytenoideus. Attacliments : bezel of the cricoid, 

 the median crest and the posterior tubercle of the ary- 

 tenoid, it dilates the entrance of the larynx ; 3 — 

 Lateral crico-arytenoideus. Attachments : Side of the 

 anterior border of the cricoid, and tubercle of the ary- 

 tenoid cartilage, it constricts the larynx ; 4 — Thyro- 

 arytenoideus. Attachments : Internal surface of the 

 ala of the thyroid and on the arytenoid ; it is a con- 

 strictor of the larynx; 5 — Arytenoideus. Attachments : 

 Median raphe and the superior part of the external face 

 of the arytenoid ; it constricts the larynx. 



Mucous membrane covered with stratified tessalated 

 epitelium on the epiglottis and the vocal cords, ciliated 



