LAKYNGEAL CAETILAGES. 



1063 



The angle which is formed by the meeting of the two laminae of the thyreoid cartilage varies, 

 to some extent, in different individuals of the same sex, and shows marked differences in the two 

 sexes and at different periods of life. In the 

 adult male the average angle is said to be 90 ; 

 in the adult female it is 120 ; whilst in the 

 infant the laminae meet in the form of a 

 gentle curve, convex ventrally. 



Cartilage triticea 



Superior cornu of 

 thyreoid cartilage 



Thyreoid notch 



Pomum Adami 



Conus elasticus 



Inferior cornu of 

 thyreoid cartilage 



Cricoid cartilage 



FIG. 845. VENTRAL ASPECT OF THE CARTILAGES 

 AND LIGAMENTS OF THE LARYNX. 



Epiglottis 



The dorsal border of each lamina of 

 the thyreoid cartilage is thick and 

 rounded, and is prolonged beyond the 

 superior and inferior borders in the 

 form of two slender cylindrical pro- 

 cesses, termed cornua. The superior 

 cornu is longer than the inferior cornu. 

 It is directed upwards, towards the 

 head, with a slight dorso- medial in- 

 clination, and ends in a rounded ex- 

 tremity, which is joined to the tip of 

 the great cornu of the hyoid bone by 

 the lateral hyo - thyreoid ligament. 

 The inferior cornu is shorter and stouter 

 than the superior cornu. As it pro- 

 ceeds downwards it curves slightly 

 towards the median plane, and upon the 

 medial face of its extremity there is a 

 circular, flat facet, by means of which 

 it articulates with a similar facet on the 

 lateral aspect of the cricoid cartilage. 



The superior border of each lamina is, for the most part, slightly convex, and, 

 ventrally, it dips suddenly to become continuous with the margin of the thyreoid 

 notch. Dorsally, where it joins the superior cornu, it exhibits a shallow notch 

 or concavity. The inferior border is almost straight, but it is marked off by a 



projection, termed the inferior thyreoid tubercle, 

 into a short clorsal part, which shows a shallow 

 concavity close to the inferior cornu and a 

 longer part which lies ventral to the tubercle, 

 and is also concave, but to a less degree. 



The lateral surface of each lamina is divided 

 into two unequal areas by the linea obliqua. 

 This line begins above at the superior thyreoid 

 tubercle, a prominence situated immediately 

 below the superior border, and a short distance 

 ventral to the root of the superior cornu. From 

 the tubercle the oblique line proceeds forwards 

 and downwards to end in the inferior tubercle 

 on the inferior border of the lamina. The area 

 which lies dorsal to the oblique line is much 

 smaller than that which lies on its ventral 

 side. It is covered by the inferior constrictor 

 muscle of the pharynx. The larger ventral 

 area is for the most part covered by the thyreo- 



hyoid muscle. To the oblique line are 

 K attached the sterno-thyreoid, thyreo-hyoid, and 



inferior constrictor muscles. The medial sur- 

 face of the lamina of the thyreoid cartilage is 

 smooth and slightly concave. 



Cartilage Cricoidea. The cricoid cartilage 

 is shaped like a signet-ring. Dorsally there is a broad, thick plate, somewhat 

 luadrilateral in form, termed the lamina ; whilst ventrally and laterally the 

 3ircumference of the ring is completed by a curved band, called the arch. The 



Hyoid bone 



Cartilago 

 tritieea 

 Hyo-thyreoid 

 membrane 



Superior 

 cornu of 

 hyoid bone 



Superior 

 tubercle on 

 the ala of 

 thyreoid 

 cartilage 



Oblique line 



Inferior tubercle 



Inferior cornu of 

 thyreoid cartilage 

 Conus elasticus 

 Cricoid cartilage 



Fn;. 846. PROFILE VIEW OF THE CARTILAGES 

 AND LIGAMENTS OF THE LARYNX. 



