THE LARYNX 67 



posterior aspect of the epiglottis and the anterior surface of the arytenoid 

 cartilages. It is deflected into the ventricles of the larynx, and next 

 passes over the vocal cords to gain the deep face of the cricoid 

 cartilage, from whence it becomes continuous with the mucous 

 membrane which lines the trachea. 



Superior Laryngeal Nerve. — This is a branch of the pneumogastric 

 nerve which is given off from the latter a little below the origin of the 

 pharyngeal nerve. It passes beneath the external carotid artery to gain 

 the wall of the pharynx. It then runs on to the outer surface of the 

 thyroid cartilage in front of the thyro-pharyngeus muscle. It gains 

 the interior of the larynx by passing through the foramen which has 

 already been mentioned as being placed near the base of the superior 

 cornu. 



On the deep face of the thyroid cartilage this nerve splits up into 

 three sets of branches ; the anterior set pass to the epiglottis and the 

 mucous membrane at the base of the tongue. The middle set are 

 distributed to the mucous membrane lining the lateral walls of the 

 larynx, whilst the posterior set pass backwards to supply the mucous 

 covering of the arytenoid cartilages and a small portion of the 

 beginning of the oesophagus. 



The intricate ramifications of this nerve endow the mucous 

 membrane of the larynx with a very high degree of sensibility. 



Near its origin this nerve gives off a motor branch which runs to 

 supply the crico-pharyngeus and crico-thyroid muscles. This branch is 

 frequently referred to as the external laryngeal nerve. 



The Inferior Laryngeal or Recurrent Laryngeal Nerve. — The right and 

 left recurrent laryngeal nerves differ as regards the seat of their origin. 

 Each is given off from the vagus ; but whereas that on the right side 

 arises at the entrance to the chest and is reflected round the arterial 

 trunk, which on this side is common to the dorsal and superior cervical 

 arteries, the recurrent nerve on the left side is given oft within the 

 chest and is reflected round the root of the posterior aorta. 



