422 HEAD AND NECK 



the lower border of the inferior constrictor muscle and becomes 

 the inferior laryngeal nerve, which ascends upon the lateral 

 aspect of the cricoid cartilage, immediately posterior to the 

 crico-thyreoid joint. There it is joined by the communicating 

 twig from the internal laryngeal nerve, and almost immediately 

 afterwards it divides into two branches. The larger of the two 

 proceeds upwards, under cover of the lamina of the thyreoid 

 cartilage, and breaks up into filaments which supply the lateral 

 crico-arytsenoid, the thyreo-arytaenoid, the vocalis and the 

 thyreo-epiglottic muscles; the smaller QI posterior branch inclines 

 upwards and posteriorly, upon the posterior aspect of the 

 cricoid cartilage, and under cover of the posterior crico- 

 arytsenoid muscle. It supplies twigs to that muscle, and is 

 then continued onwards to end in the arytaenoid muscles. 



The inferior laryngeal nerve is, therefore, the motor nerve 

 of the larynx. It supplies all the muscles with the exception 

 of the crico-thyreoid, which obtains its nerve-supply from the 

 external laryngeal. The inferior laryngeal nerve, however, 

 contains a few sensory fibres also. These it gives to the 

 mucous membrane of the larynx below the rima glottidis. 



Laryngeal Arteries. The superior laryngeal artery ', a 

 branch of the superior thyreoid, accompanies the internal 

 laryngeal nerve ; the inferior laryngeal artery, which springs 

 from the inferior thyreoid, accompanies the inferior laryngeal 

 nerve. These two vessels ramify in the laryngeal wall and 

 supply the mucous membrane, glands, and muscles. 



Laryngeal Cartilages and Joints. The cartilages which 

 constitute the skeleton of the larynx and give support to its 

 wall are the following : 



2 Cricoid d ' } 4- Aryuenoid, ] 



3'. Cartilage of the f sin S le ' 5- Corniculate, paired, 



epiglottis, J 6 " Cuneiform, 



They are connected by certain ligaments. 



Dissection. The mucous membrane and muscles must be carefully 

 removed from the cartilages, and the ligaments must be defined. Great 

 caution must be exercised in cleaning the arytaenoid cartilages and the 

 corniculate cartilages, in order that the latter may not be injured. 



Cartilage Epiglottica. The epiglottic cartilage is a thin, 

 leaf-like lamina of yellow fibro-cartilage which is placed posterior 

 to the tongue and the body of the hyoid bone, anterior to 

 the upper aperture of the larynx. When divested of the 



