146 A MANUAL OF ANATOMY. 



Action. To approximate the two cartilages and thus 

 make tense the vocal cords. 



Posterior Crico-arytenoid. 



Arises from the quadrilateral posterior surface at the 

 side of the median ridge of the cricoid cartilage. 



It is inserted into the outer angle of the base of the 

 arytenoid cartilage. The action is to slacken the vocal 

 cords and widen the rima glottidis. 



Arytenoideus. 



Crosses from one arytenoid cartilage to the other. In 

 action it draws together the arytenoid cartilages, thus 

 narrowing the rima glottidis. 



Aryteno-epig-lottidis. 



The name applied to a small bundle of fibres connecting 

 the arytenoid cartilage with the aryteno-epiglottic fold. It 

 is a part of the arytenoideus. 



Arteries passing into the larynx. 



The superior laryngeal branch of the superior thyroid 

 and the inferior laryngeal branch of the inferior thyroid 

 artery. 



Nerves of the larynx. 



The superior and inferior laryngeal branches of the 

 pneumogastric. 



DISSECTION. 



Remove these external muscles, clean the fibrous membranes connecting 

 the thyroid cartilage to the hyoid bone (thyrohyoid membrane), and that 

 uniting the cricoid and thyroid cartilages (cricothyroid membrane). These 

 membranes have to be divided in the operations of opening the larynx or the 

 larynx and trachea. 



Remove one-half of the larynx. 



Above the false vocal cord is the fossa innominata ; be- 

 tween the false and true cords the ventricle. 

 Muscles of the Interior of the Larynx. 



