442 



RESPIRATORY SYSTEM OF THE HORSE 



Facet for 

 arytenoid 



Anterior 

 border 



Facet for 

 tfiyroid 



Posterior 



border 



Arch 



Fig. 350. — Cricoid C.\rtil.\ge of Horse, Left Later.^l 

 View. 



lamina is thick and slightly concave; the posterior border is thin and irregularly- 

 notched. The anterior border of the arch is concave ventrallj^ and gives 

 attachment to the crico-thyroid membrane; laterally it is thicker and gives 



attachment to the crico-aryten- 

 Median ridge Lamina oideus lateralis muscle. The pos- 



terior border is attached to the 

 first ring of the trachea by an 

 elastic membrane. The inner sur- 

 face is smooth and is covered with 

 mucous membran(\ 



The th3rroid cartilage ( Cartilage 

 thyreoidea) consists of a median 

 thickened portion, termed the 

 body, and two lateral laminae or 

 wings. The body forms ventrally 

 a slight prominence (Prominentia 

 laryngea), which can be felt, but 

 is not visible in the living sub- 

 ject; it supports the base of the 

 epiglottis, which is attached to it 

 by an elastic ligament. The wings 

 or laminae spring from the body 

 on either side and form a large 

 part of the lateral wall of the larynx. Each is a rhomboid plate, presenting a 

 slightly convex outer surface, which is divided into two areas by an oblique line 

 (Linea obliqua), on which the thyro-hyoid and thyro-pharyngeus muscles meet. 

 The superior (dorsal) border is nearly 

 straight; it gives attachment to the Body 



pharyngeal fascia and the palato- 

 pharyngeus muscle, and bears a cornu 

 at each end. The anterior comu 

 (Cornu oralc) is attached to the 

 thyroid cornu of the hyoid bone; 

 below it is a notch, which is con- 

 verted into a foramen (Foramen thy- 

 reoidcum) by a fibrous band, and 

 transmits the superior laryngeal nerve 

 to the interior of the larynx. The 

 posterior cornu (Cornu caudale) articu- 

 lates with the cricoid cartilage. The 

 inferior (ventral) border is fused with 

 the body in front; behind, it diverges 

 from its fellow to inclose a triangular 

 space (Incisura thyreoidea caudalis), 

 which is occupied l)y the crico-thyroid 

 memi)rane. The anterior border is 

 slightly convex, and is attached to the 

 hyoid bone by the thyro-hyoid mem- 

 brane. The posterior border overlaps 

 the arch of the cricoid cartilage, and 

 gives attachment to the crico-thyroid 



muscle. The inner surface is concave, and is covered by mucous membrane to a 

 small extent. 



The epiglottis (Cartilago epiglottica) is situated above the body of the thyroid 



Thyroid notch 



}Ying 

 Anterior cornu 



Thyroid fora- 

 men 



Posterior cornu 

 Surface for articu- 

 lation with cricoid 



Fi(i. 351. — Thyroid ("artilagk of Horse, Ventral 

 \'ii.w. 



