134 



PHYSIOLOGY 



CHAP. 



cricoid plate on both sides of the median line by oval saddle-shaped 

 joints, which allow of their rotation on their base, and the dis- 

 placement of the base inward or outward. The stout crico- 

 arytenoid ligament controls the back to front movement of the 

 arytenoids. At the summit of the latter comes the articulation of 

 the two little cartilages of Santorini (Figs. 87, 88, 89). 



The thyroid cartilage is attached to the hyoid bone, which lies 

 above it, by a fibrous membrane, the thyro-hyoid (known in its 

 middle portion as the ligamentum thyreo-hyoideum lateralis), and 

 by the lateral thyro-hyoid ligament, which runs from the superior 

 cornua of the thyroid to the great cornua of the hyoid. By means 



/ '"-T 



FIG. 88. (Left.) t, thyroid, and cr, cricoid cartilages, from the side. (Henle.) 



FIG. 89. (Right.) Laryngeal cartilages divided through the median -sagittal plane, and viewed 

 from within. (Henle.) t, thyroid cartilage ; Cs, its upper horn ; Pv, processus vocalis of 

 arytenoid ; co, cartilage of Santorini ; cr, cricoid cartilage. 



of these membranes and ligaments the whole larynx can be drawn 

 upwards. 



Behind the thyro-hyoid membrane is the epiglottis, which is 

 attached below the thyro-epiglottidean ligament to the median 

 notch of the thyroid, and projects into the pharyngeal cavity in the 

 form of a tongue which is folded back in swallowing and forms a 

 lid for the upper opening of the larynx (Figs. 90, 91, 92). 



On both sides of the free portion of the epiglottis the mucous 

 membrane forms a fold that unites the upper margin of this 

 cartilage with the cartilages of Santorini. In the depth of this 

 aryteno-epiglottidean fold there is a group of mucous glands and a 

 nodule known as the cuneiform cartilage, or cartilage of Wrisberg. 

 The aryteno-epiglottidean fold limits the upper opening of the 

 larynx ; it is oval in form and is inclined backwards and downwards. 



The laryngeal cavity narrows into the glottis or rima glottidis. 



