THE LARYNX AND THE EAR 



355 



has the general shape of a signet ring and is so placed 

 that the part corresponding to the signet fits into the thy- 

 roid space, while the ring portion encircles the larynx just 

 below the thyroid. Muscles and connective tissue pass 

 from the thyroid to the cricoid cartilage at all places, save 

 one on each side, where the downward projections of the 

 thyroid form hinge joints with the cricoid. These joints 

 permit of motion of either cartilage upon the other. 



At the summit of the cricoid cartilage, on each side, is 

 a small piece of triangular shape, called the arytenoid 

 cartilage. Each arytenoid is movable on the cricoid and 

 is connected with one end of a vocal cord. 



The Vocal Cords are formed by two narrow strips of 

 tissue which, connecting with the thyroid cartilage in front 

 and the arytenoid cartilages behind, lie in folds of the 

 mucous membrane. They have the general appearance 

 of ridge-like projections from the sides of the larynx, but 



Epiglottis 

 False Vocal Cords 



True Vocal Cords 



A 



FlG. 150. Vocal cords as seen from above. A. In producing sound. 

 . During quiet breathing. 



at their edges they are sharp and smooth. The open space 

 between the cords is called the glottis. When sound is 

 not being produced, the glottis is open and has a triangular 

 form, due to the spreading apart of the arytenoid cartilages 

 and the attached cords. But when sound is being pro- 

 duced, the glottis is almost completely closed by the cords. 

 Above the vocal cords, and resembling them in appear- 



