ARYTEXOID CARTILAGES. 



907 



descends with a deep concavity in front below the thyroid cartilage ; "while 

 the inferior border is horizontal, and connected by membrane to the first 

 ring of the trachea. The posterior elevated part of the upper border is 

 slightly notched in the middle line ; and on the sides of this notch are two 

 convex oval articular facets, directed upwards and outwards, with which the 

 arytenoid cartilages are articulated. The external surface of the cartilage 

 is convex and smooth in front and at the sides, where it affords attachment 

 to the crico-thyroid muscles, and behind these to the inferior constrictor 

 muscle on each side : posteriorly it presents in the middle line a slight ver- 

 tical ridge, to which some of the longitudinal fibres of the oesophagus are 

 attached. On each side of this ridge is a broad depression occupied by the 

 posterior crico-arytenoid muscle, and externally and anteriorly to that a small 

 rounded and slightly raised surface for articulation on either side with the 

 inferior cornu of the thyroid cartilage. The internal surface is in contact 

 throughout with the mucous membrane of the larynx. The lower border 

 of the cricoid cartilage i* circular, but higher up it is somewhat compressed 

 laterally, so that the passage through it is elliptical 



The arytenoid cartilages are two in number, and are of a symmetrical 

 form. They may be compared to three-sided pyramids recurved at the 

 summit, resting by their bases on the posterior and highest part of the 

 cricoid cartilage, and approaching near to one another. Each measures 

 from five to six lines in height, about three lines in width, and, in 

 the middle of its inner surface, more than a line from before backwards. 

 Of the three faces, the posterior is broad, triangular, and excavated from 

 above downwards, lodging part of the arytenoid muscle. The anterior 



Fig. 635. 



Fig. 635. OUTLINE SHOWING THE 



POSITION AND FOBM OF THE ARY- 

 TENOID CARTILAGES FROM BEHIND, f 



A, hyoid bone ; t, the superior, and 

 t! t the inferior cornu of the thyroid 

 cartilage ; c, placed on the median 

 ridge of the back of the cricoid carti- 

 lage ; a, placed between the two ary- 

 tenoid cartilages, to which the letter 

 points by two dotted lines ; the carti- 

 lages of Santorini or cornicula are 

 shown above the upper angles ; tr, the 

 trachea. 



surface, convex in its general 



outline, and somewhat rough, 



gives attachment to the thyro- 



arytenoid muscle, and, by a small 



tubercle, to the corresponding 



superior or false vocal cord. The 



internal surface, which is the 



narrowest of the three, and 



slightly convex, is nearly parallel 



with that of the opposite cartilage, 



being covered by the laryngeal 



mucous membrane. The anterior and posterior borders, which limit the 



internal face, ascend nearly in the same vertical plane, whilst the external 



border, which separates the anterior from the posterior surface, is directed 



obliquely upwards and inwards. 



