Chap. XIII] 



RESPIRATORY SYSTEM 



235 



THE LARYNX 



The larynx is situated between the base of the tongue and 

 the top of the trachea, in the upper and front part of the neck. 

 Above and behind lies the pharynx, which opens into the oesoph- 

 agus, or gullet, and on either side of it lie the great vessels of 

 the neck. In form, the larynx is narrow and rounded below, 



Fig. 141. — Larynx. Viewed from above. (Gerrish.) 



where it blends with the trachea, but broad above and shaped 

 somewhat like a triangular box, with flat sides and prominent 

 ridge in front. It is made up of nine pieces of fibro-cartilage, 

 united together by elastic ligaments, and moved by numerous 

 muscles. 



The three principal cartilages are the cricoid, thyroid, and 

 epiglottis. The cricoid resembles a seal ring with the hoop part in 

 front and the signet part in the back. The thyroid resembles 

 a shield and is the largest. It rests upon the cricoid and con- 

 sists of two square plates, or alse (right and left), which are joined 

 together in front and form by their union the laryngeal promi- 

 nence, called Adam's apple. The upper portion of the hind 

 border of the thyroid is called the superior horn, and the lower 

 portion the inferior horn (see Fig. 143). The epiglottis is 

 shaped like a leaf. The stem is inserted in the notch between 

 the two plates of the thyroid. The larynx is lined throughout 



