428 HEAD AND NECK 



surface is narrow, vertical, and even, and is clothed with 

 mucous membrane. The posterior surface is concave ; it 

 lodges and gives attachment to the arytaenoideus transversus 

 muscle. The antero-lateral surface is the most extensive of 

 the three, and is uneven for muscular and ligamentous attach- 

 ments. Upon this aspect of the arytaenoid cartilage the 

 musculus vocalis and the thyreo-arytaenoid muscles are in- 

 serted. The surfaces of the arytaenoid cartilage are separated 

 by three borders, viz., an anterior, a posterior, and a lateral. 

 The lateral border is the longest, and, at the base of the 

 cartilage, it is prolonged postero-laterally in the form of a 

 stout prominent angle or process, termed the processus muscu- 

 laris. It gives attachment anteriorly to the crico-arytaenoideus 

 lateralis muscle; and posteriorly to the crico-arytaenoideus 

 posterior. The anterior border of the arytaenoid cartilage is 

 prolonged into the projecting anterior angle of the base. 

 This is called the processus vocalis. It is sharp and pointed, 

 and gives attachment to the vocal ligament (O.T. true vocal 

 cord). The base of the arytaenoid cartilage presents an 

 elongated concave facet, on its under aspect, for articulation 

 with the upper border of the lamina of the cricoid cartilage. 



Crico-arytsenoid Joints. These articulations are of the 

 diarthrodial variety. There is a distinct joint cavity sur- 

 rounded by a capsular ligament, which is lined with a synovial 

 stratum. The cricoid articular surface is convex, that of 

 the arytaenoid concave ; both are elongated in form, but they 

 are placed in relation to each other so that the long axis of 

 the one intersects or crosses that of the other, and in no 

 position of the joint do the two surfaces accurately coincide. 

 The movements allowed at this joint, as the dissector can 

 readily determine, are of a twofold kind (i) gliding, by 

 which the arytaenoid is carried medially or laterally, or, in 

 other words, a movement by which the arytaenoid advances 

 towards or retreats from its fellow; (2) rotatory, by which the 

 arytaenoid cartilage revolves round a vertical axis. By this 

 movement the vocal process is swung laterally or medially, so 

 as to open or close the rima glottidis. 



The dissector should note that the capsule of this joint 

 is strengthened posteriorly by a strong band which plays a 

 most important part in the mechanism of the articulation. 

 It restricts movement of the arytaenoid cartilage. 



Cartilagines Cuneiformes. These are two little rod-shaped 



