94 



TOPOGRAPHICAL ANATOx\lY OF THE 



the lamina by a narrow thyroid Jissmx (fissura thyreoidea), which is con- 

 verted into a foramen by a membranous ligament continuous with the 

 hyo-thyroid membrane. By means of this foramen the cranial laryngeal 

 nerve gains the interior of tlie larynx. The cranial or anterior borders 

 of the two laminte are connected with the byoid bone by the hyo- 

 thyroid membrane (membrana hyothyreoidea). The ventral borders 

 meet at the laryngeal prominence only. Behind this they are separated 

 by a deep triangular caudal thyroid notcli (incisura thyreoidea caudale), 

 which is filled by the crico-thyroid ligament (ligamentum crico- 

 thyreoideum). The caudal border of each lamina overhangs the arch of 

 the cricoid cartilage, and affords attachment to the crico-thyroid muscle. 

 The lateral surface of the lamina is slightly convex, and is crossed by a 



Muscular process. Arytenoid cartilage. 



Corniculate cartilage. 



Lamina of cricoid cartilage. 



Thyroid articular surface. 



Arch of cricoid cartilage. 



Arytenoid articular surface 



I ■■ Cuneiform cartilage. 

 [ Laryngeal prominence. 



Thvroid cartilage. 



Posterior cornu. 



Fig. 36. — The laryngeal cartilages. 



faint oblique line (linea obliqua), to which the thyro-hyoid muscle is 

 inserted. The concave medial surface is smooth, and partly covered by 

 the mucous membrane that lines the interior of the larynx. 



The cricoid'^ cartilage (cartilage cricoidea) is placed behind the 

 thyroid, by the laminae of which it is partially covered laterally. In 

 form it has a resemblance to a signet ring, and is, therefore, divisible 

 into a narrow arch, ventral and lateral in position, and a broader dorsal 

 portion or lamina. The arch is narrowest in its most ventral part 

 where its cranial border forms a wide and shallow notch. Its caudal 

 border is connected with the first ring of the trachea, and its lateral 

 surface is grooved for the reception of the crico-thyroid muscle. In the 

 middle of the cranial border of the lamina there is a shallow notch, and 

 on each side of this an oval, convex facet for articulation with one of 

 ' KpiKos (kiikos) [Gr.], a finger-ring. d5os (eidos) [Gr.], form. 



