THE HEAD AND NECK 1293 



Having ascended in the groove between the trachea and oesoph- 

 agus, it passes beneath the lower border of the inferior con- 

 strictor muscle, and ascends upon the cricoid cartilage, lying close 

 behind the crico-thyroid joint. Here it divides into two branches, 

 anterior and posterior. The anterior branch ascends under cover 

 of the thyroid cartilage, and is distributed to the lateral crico- 

 ar^iienoid, thyro-arytenoid, thyro-epiglottideus, and aryteno-epi- 

 glottideus muscles. The posterior branch passes upwards on the 

 back of the cricoid cartilage beneath the posterior crico-arytenoid 

 muscle, which it suppUes, and then it goes on to end in the arytenoid 

 muscle. 



The recurrent laryngeal nerve furnishes some sensory branches 

 to the mucous membrane of the larynx below the rima glottidis, 

 and it communicates with the internal branch of the superior 

 laryngeal. The motor fibres of the external branch of the superior 

 laryngeal and of the inferior laryngeal are derived from the bulbar 

 portion of the spinal accessory nerve. 



Summary ol the Laryngeal Nerves. — The superior laryngeal nerve, through 

 its internal branch, is sensory, and its external branch supplies the crico- 

 thyroid muscle, and, in part, the inferior constrictor muscle of the pharynx. 



The inferior or recurrent laryngeal nerve is chiefly motor, and it supplies 

 the intrinsic muscles of the larynx, with the single exception of the crico-thyroid 

 muscle. 



Arteries. — ^The arteries of the larynx are the superior and the 

 inferior laryngeal. The superior laryngeal artery is a branch of 

 the superior thyroid. It accompanies the internal larjTigeal nerve, 

 below which it lies, and enters the larynx by piercing the thyro- 

 hyoid membrane. The inferior laryngeal artery is a branch of 

 the inferior thyroid, and it accompanies the inferior or recurrent 

 laryngeal nerve. 



Veins. — The superior laryngeal vein opens into the superior 

 thyroid, and the inferior laryngeal vein into the inferior thyroid 

 vein. 



Lymphatics. — ^These are arranged in two sets — superior and 

 inferior. The superior lymphatics come from the portion of the 

 larynx above the rima glottidis. Having pierced the thyro-hyoid 

 membrane, they pass to the upper group of deep cer\acal glands. 

 The inferior lymphatics come from the portion of the larynx below 

 the rima glottidis. Having pierced the crico-thyroid membrane, 

 they pass to the lower group of deep cervical glands, having 

 previously traversed the prelaryngeal glands. 



In early life the larynx occupies a higher position than it does 

 in the adult, its descent, which is gradual, being completed by 

 puberty. Up to that period the projection known as the pomum 

 Adami is not present. After puberty important changes take place. 

 The cartUages increase in size, the pomum Adami assumes marked 

 development, especially in the male, and the true vocal cords 

 undergo increase in length. These various changes account 

 for the modifications which the voice undergoes at and after 

 puberty. 



