THE THYROID AND CRICOID CARTILAGES. 



699 



the lower, and in consequence of this form the larynx is somewhat 

 funnel-shaped. The fore part is prominent in the middle line in 

 front, forming the subcutaneous swelling named the pomum Adami, 

 and concave behind, where it gives attachment to the epiglottis, and 

 to the thyro-arytenoid muscles and ligaments. The upper border is 

 notched in the centre. 



The cartilage consists of two squarish halves or alee, which are 

 united in front. Posteriorly each 

 ala has a thick border, which i- 

 continued upwards and down- 

 wards into a rounded process or 

 ml F). Both cornua 

 aiv bent slightly inwards : of 

 the two, the upper (E) is the 

 longer ; but the lower one (F) 

 is the thicker, and articulates 

 with cricoid cartilage. The 

 inner surface of the ala is 

 smooth ; the outer is marked by 

 an oblique line for the attach- 

 ment of muscles, which extends 

 from a tubercle near the root of 

 the upper cornti, to a projec- 

 tion at the middle of the lower 

 border. 



The CRICOID CARTILAGE (D) IS 



stronger though smaller than the 

 thyroid, and surrounds the lower 

 part of the cavity of the larynx ; 

 it is partly concealed by the 

 thyroid cartilage, below which 

 it is placed. It is something like 

 a signet ring, being very unequal 

 in depth before and behind, 

 the posterior part being nearly 

 four times as deep as the anterior, 

 ntained space is about as 

 large as the forefinger. 



At the back of the cartilage 



is con vex in 

 front, 



concave 

 behind: 



formed of 

 two alae, 

 each having 

 upper and 

 lower 

 cornua. 



FIG. 248. HYOID BONE AND LARYX- 

 GEAL CARTILAGES. 



Cricoid 

 cartilage 



form ; 



C.C. 

 D. 



Epiglottis. 

 Thyroid cartilage. 

 Arytenoid cartilages. 

 Cricoid cartilage. 



E. Upper cornu. 



F. Lower cornu of thyroid carti- surfaces; 



lage. 

 G. 



Body of hyoid bone. 

 Large cornu. 

 Small cornu. 



there is a flat and rather square 

 portion, which is marked on its 

 posterior surface by a median 

 ridge between two oval depres- 

 sions which are occupied by the posterior crico-arytenoid muscles. On 

 each side, immediately in front of the square part, is a slightly raised 

 articular facet, which receives the lower cornu of the thyroid cartilage. 

 The inner surface is smooth, and is covered by mucous membrane. 



The lower border is horizontal, somewhat undulating, and is borders, 

 united to the trachea by fibrous membrane. The upper border of 



