1210 



THE RESPIRATORY SYSTEM 



The cricoid cartUage [cartilago cricoidea] (figs. 973, 974, 975, 978), single, has 

 been compared in its shape to a signet ring. Its position is at the lower end of 

 the larynx, where it is connected with the first ring of the trachea. Posteriorly 

 the cricoid cartilage expands into a broad lamina [lamina cartilaginis cricoideae] 

 which enters into the posterior boundary of the laryngeal cavity, while laterally 

 and in front it forms a narrow arch [arcus cartilaginis cricoideae]. On either side 

 of the upper margin of the lamina is the elliptical arytaenoid articular surface 

 [facies articularis arytsenoidea] its long axis parallel with the margin of the cricoid. 

 Its steeply sloping surface convex for articulation with the arytaenoid cartilage.' 

 The hinder surface of the lamina presents a median ridge and lateral impressions 

 for the attachment of the posterior crico-arytaenoid muscles. The arch, weakest 



Fig. 972.— Median Section of a Man 21 Years of Age, showing the Position op Larynx 

 AND Trachea. (After W. Braune, from Poirier and Charpy.) 



Pharynx 



„ Arytaenoid 



cartilage 



j^ \ \ V " "■"■" .'.'11.._ ^"Ventricular fold 



., Vocal fold 



\VI cervical 

 vertebra 



-I thoracic 

 vertebra 



.V thoracic 

 vertebra 



Epiglottis 



Hyoid bone 



Laryngeal 



aperture 



Fat mass 



Laryngeal 



ventricle 



Thyreoid 



cartilage 



Lamina of 



cricoid 



Arch of cricoid 



Trachea 



CEsophagus 



Thyreoid body. 



Sterno- 



thyreoid m.' 



Sternum 



Left innominate 



vein 



Innominate 

 artery 



Bifurcation of 

 trachea 



Ascending aorta 



Right lung 



Right auricle- 



in its middle part, presents cancave upper and straight lower margins. A circular, 

 elevated thyreoid articular surface [facies articularis thyreoidea] for articulation 

 with tlio inferior coruu of the thyreoid cartilage is situated upon the side of the 

 cricoid w1ht(! arch and lamina are continuous. The internal surface is covered by 

 the laryngeal mucosa. 



The thyreoid cartilage [cartilago thyreoidea] (figs. 973, 974, 975, 977), single 

 and the largest in the laryngeal skeleton is composed of two broad laminae, 

 right and left, which meet and are fused anteriorly in the mid-line in a right angle, 

 partly covering the other cartilages laterally and in front. 'J'he lamina; are stout, 

 but their connection at the angle is through a weak strip of cartilage. The upper 

 margin of each lamina is convex, and in front drops abruptly to form in the median 

 line the superior thyreoid notch [incisura thyreoidea superior]. The anterior edges 



I 



