158 DISSECTION OF THE LARYNX. 



NERVES. The nerves of the larynx are the superior and inferior laryn- 

 geal branches of the pneumo-gastric (p. 113); the former is distributed 

 to the mucous membrane, and the latter chiefly to the muscles. 



The inferior laryngeal nerve (recurrent), when about to enter the 

 larynx, furnishes backwards an offset to the mucous membrane of the 

 pharynx ; this joins filaments of the upper laryngeal. The nerve then 

 passes beneath the ala of the thyroid cartilage, and ends in branches for 

 all the special muscles of the larynx except the crico-thyroideus. Its 

 small muscular branches are superficial, but that to the arytaenoid muscle 

 passes beneath the crico-arytrenoideus posticus. Beneath the thyroid car- 

 tilage the inferior is joined by a long offset of the upper laryngeal nerve. 



The superior laryngeal nerve pierces the thyro-hyoid ligament, and 

 gives offsets to the mucous membrane of the pharynx ; it furnishes also a 

 long branch beneath the ala of the thyroid cartilage to communicate with 

 the recurrent nerve. The trunk then terminates in many branches for the 

 supply of the mucous membrane : Some of these ascend in the arytfeno- 

 epiglottid fold to the epiglottis, and the root of the tongue. The others, 

 which are the largest, descend on the inner side of the ventricular pouch, 

 and supply the lining membrane of the larynx as low as the vocal cords. 

 One nerve of this set pierces the arytaenoid muscle, and ends in the mucous 

 membrane. 



VESSELS. The arteries of the larynx are furnished from the superior 

 and in erior thyroid branches (p. 85 and 78). 



The laryngeal branch of the superior thyroid artery enters the larynx 

 with the superior laryngeal nerve, and divides into ascending and descend- 

 ing branches ; some of these enter the muscles, but the rest supply the 

 epiglottis, and the mucous membrane from the root of the tongue to the 

 chorda vocalis. Like the nerves, it unites with the following artery both 

 beneath the ala of the thyroid cartilage, and in the mucous membrane of 

 the pharynx. 



The laryngeal branch of the inferior thyroid artery ascends on the 

 back of the cricoid cartilage, and ends in the mucous membrane of the 

 pharynx and the posterior muscles of the larynx. 



Some other twigs from the superior thyroid artery perforate the crico- 

 thyroid membrane, and ramify in the mucous lining of the interior of the 

 larynx at the lower part. 



Laryngeal veins. The vein accompanying the branch of the superior 

 thyroid artery, joins the internal jugular or the superior thyroid vein ; 

 and the vein with the artery from the inferior thyroid opens into the 

 plexus of the inferior thyroid veins (p. 85 and 78). 



SECTION XVII. 



HYOID BONE, CARTILAGES AND LIGAMENTS OF THE LARYNX, AND 

 STRUCTURE OF THE TRACHEA. 



Dissection. All the muscles and the mucous membrane are to be 

 taken away so as to denude the hyoid bone, the cartilages of the larynx, 

 and the epiglottis ; but the piece of membrane that joins the hyoid bone 



