S20 



SPECIAL MUSCULAK MECHANISMS. 



The principal cartilages are the thyroid, cricoid, the two arytenoid, and 

 the epiglottis. 



The thyroid cartilage is the largest and consists of two quadrilateral 

 plates or alee, which are continuous with each other in front, where they 

 form the prominence called the pomum Adami. The posterior borders of 

 the thyroid cartilage serve as a point of attachment of the stylo-pharyngeus 

 and palato-pharyngeus muscles. The upper part of each of these borders 

 terminates in a superior cornu, which articulates with the hyoid bone ; the 

 lower portion terminates in the inferior cornu, which articulates with the 

 cricoid cartilage. The upper border between the cornua is connected with 



FIG. 204. 



Median Section of Mouih, Nose, Pharynx, and Larynx, a, septum of nose, below it section 

 of hard palate ; b, tongue ; c, section of velum pendulum palati ; d, d, lips ; u, uvula ; r, anterior 

 arch or pillar of fauces : i, posterior arch ; t, tonsil ; p, pharynx : h, hyoid bone ; k, thyroid carti- 

 lage ; n, cricoid cartilage ; s, epiglottis ; v, glottis ; 1, posterior opening of the nares; 3, isthmus 

 faucium ; 4, superior opening of larynx ; 5, passage into oesophagus ; 6, mouth of right Eustachian 

 tube. 



the hyoid bone by the thyro-hyoid membrane. The lower border is con- 

 nected with the cricoid cartilage by the thyro-cricoid membrane at the 

 median line, and at the sides by the crico-thyroid muscles. 



The cricoid cartilage is situated below the thyroid cartilage with its broad 

 portion posteriorly. At the upper part of its broad portion are two smooth 

 surfaces on which the arytenoid cartilages articulate. 



The arytenoid cartilages are pyramidal in form and articulate on the 

 upper surface of the cricoid. Each cartilage has an external, posterior, and 

 internal (median) surface, an apex and a base. The apex is pointed back- 

 ward and inward, and is surmounted by a small cartilaginous tubercle, called 

 the cartilage of Santonin (Fig. 207). The base, which articulates with the 

 cricoid cartilage, presents at its external internal angle a projection called 

 the processus vocalis. At the posterior internal angle is a second projection, 

 called the processus muscularis. 



754. The superior opening of the larynx is formed anteriorly by the 

 epiglottis, posteriorly by the apices of the arytenoid cartilages, and laterally 

 by the aryteno-epiglottidean folds stretching between these points. The in- 



