1064 



THE EESPIEATOEY SYSTEM. 



Hyoid bone 



Cartilago triticea 



Thyreo-epiglottic 

 ligament 



Superior cornu o. 

 thyreoid cartilage 



lumen of the ring enclosed by these parts is circular below, but the upper part 

 of the ring is compressed laterally, so that the lumen becomes elliptical. The 

 upper border of the lamina presents a faintly marked median notch. On either 

 side of this there is an oval facet which looks more laterally than upwards; it 

 articulates with the base of the arytaenoid cartilage. The dorsal surface of the 

 lamina is divided by an elevated median ridge into two depressed areas which 

 give attachment to the posterior crico-arytaenoid muscles. The ventral part of 

 the arch of the cricoid is in the form of a narrow band, but as it proceeds 

 dorsally towards the lamina its upper border rises rapidly, and in consequence 

 the arch becomes much broader. The inferior border of the cricoid is nearly 

 straight, although it frequently presents a median ventral projection and two 

 lateral projections. It is joined to the first ring of the trachea by an elastic 

 membrane the crico-tracheal ligament. On the lateral surface of the cricoid 

 cartilage, at the place where the arch joins the lamina, a vertical ridge runs 



downwards from the arytaenoid 

 articular facet. On this, a short 

 distance from the inferior border 

 of the cartilage, a prominent cir- 

 cular articular facet is visible, for 

 articulation with the inferior cornu 

 of the thyreoid cartilage (Fig. 848, 

 p. 1067). The medial surface of the 

 cricoid cartilage is smooth, and is 

 covered with mucous membrane. 



The narrow band - like part of 

 the arch of the cricoid cartilage lies 

 below the inferior border of the' 

 th y reoid cartilage, whilst the lamina i 

 is received into the interval between 

 the dorsal portions of the laminae^ 

 of the thyreoid cartilage. 



Cartilagines Arytaenoideae. 

 The arytsenoid cartilages are placed! 

 one on each side of the median ; 

 plane, and rest upon the upper 

 border of the lamina of the cricoid! 

 cartilage, in the interval betweecj 

 the dorsal portions of the lamina 

 of the thyreoid cartilage. Each 

 presents a somewhat pyramida 

 form, the pointed apex of which ii 

 directed upwards, and at the sann 

 time curves dorsally and medially 



It supports the corniculate cartilage (Santorini). Of the three surfaces, the media 

 one faces the corresponding surface of the opposite cartilage, from which it is separate< 

 by a narrow interval ; another looks dorsally ; whilst the third is directed lateral!; 

 and ventrally. The medial surface, which is the smallest of the three, is triangula 

 in outline. It is narrow, vertical, and even, and is clothed with the lining mucou 

 membrane of the larynx. The dorsal surface is smooth and concave in the cranic 

 caudal direction ; it lodges and gives attachment to the arytaenoideus transverse 

 muscle. The ventro-lateral surface is the most extensive of the three (Fig. 84! ; 

 p. 1067). Its middle part is marked by a deep depression in which is lodged a mass < 

 mucous glands. Upon this surface of the arytaenoid cartilage the vocalis and thyre< 

 arytaenoid muscles are inserted, whilst a small tubercle a short distance above tl: 

 base gives attachment to the ventricular ligament the feeble supporting ligamei 

 of the ventricular fold (O.T. false vocal cord). The three surfaces of the arytaeno : 

 cartilages are separated from each other by a ventral, a dorsal, and a lateral borde 

 The lateral border is the longest, and it pursues, as it is traced from the apex to tl 

 base, a sinuous course. Eeaching the base of the cartilage, it is prolonged lateral 



Muscular process of 

 arytsenoid cartilage 



Inferior cornu of 

 thyreoid cartilage 



FIG. 847. DORSAL ASPECT OF THE CARTILAGES 

 AND LIGAMENTS OF THE LARYNX. 



