THE HEAD AND NECK 1*79 



convex facet for articulation with the base of the arytenoid carti- 

 lage. The posterior surface is divided into two depressed areas by 

 a median vertical ridge, which gives attachment to the longitudinal 

 muscular fibres of the oesophagus. The depressed area on either 

 side of this median vertical ridge gives origin to the posterior crico- 

 arytenoid muscle. 



The oider surface of the cricoid cartilage presents posteriorly a 

 circular facet for articulation with the inferior comu of the ala of 

 the th)?roid cartilage. The upper sloping border of this part gives 

 attachment, cJong its inner margin, to the lateral portion of the 

 crico-thyroid membrane. 



The internal surface of the cricoid cartilage is lined with the mucous 

 membrane of the larynx. 



Development. — The cricoid cartilage, like the rings of the trachea, is 

 developed in the mesoblast of the respiratory tnbe. 



Arytenoid Cartilages. — These cartilages, which are two in number, 

 surmoimt the superior border of the cricoid cartilage posteriorly. 

 Each has the form of a three-sided pyramid, and measures about 

 J inch in height, and about \ inch in width at the base. The apex 

 looks upwards, and is curved in a backward and inward direction. 

 It is surmoimted by the comiculum laryngis. The base looks down- 

 wards, and is slightly concave and facetted to articulate with the 

 superior border of the cricoid cartilage posteriorly. Two of the 

 three angles of the base are promiaent, namely, the anterior and 

 the external. The anterior angle, 



somewhat pointed, is directed Comicalum Laryngis 



straight forwards, and is known as ^^ 



the vocal process. It gives attach- /3 



ment to the inferior thyro-ary- ^'t«'°»'B«**«*-y^— Anterior Borier 

 tenoid ligament or true vocal cord. /J**" VVocai Pionss 



The external angle, thick and some- ^""^"^ ^*"*^ ^J^k>^ 

 what round, has an inclination Base 



backwards, as weU as outwards, fig. 528.— The Right Arytenoid 

 and IS known as the musciUar Cartilage and Cornicux,um 

 ■process. Anteriorly it gives in- Laryngis (External View). 



sertion to the crico-arytaenoideus 



lateralis, and posteriorly to the crico-arytaenoideus posticus. The 

 surfaces are antero-extemal, posterior, and internal. The antero- 

 external surface, a little above the vocal process, gives attachment 

 to the, superior thyro-arytenoid ligament or false vocal cord, and, 

 above and external to the voCal process, to the thyro-arytaenoideus 

 muscle. The posterior surface is triangular and conca\-e, and gives 

 attachment to a portion of the arytaenoideus muscle. The internal 

 surface faces its fellow of the opposite side, and is covered by mucous 

 membrane. It forms the posterior part of the lateral boimdary 

 of the rima glottidis. The borders are anterior, posterior, and ex- 

 ternal. The anterior border separates the internal from the antero- 

 extemal surface, and terminates below in the vocal process. The 

 posterior border separates the internal from the posterior surface. 



