442 



RESPIRATORY SYSTEM OF THE HORSE 



Facet for 

 arytenoid 



Anterior 

 border 



Facet for 

 thyroid 



Posterior 



border 



Arch 



Fig. 



350. — Cricoid Cartilage of Horse, Left Lateral 

 View. 



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



notched. The anterior border of the arch is concave ventrally 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 membrane. 



The thyroid cartilage (Cartilago 

 thyreoidea) consists of a median 

 thickened portion, termed the 

 body, and two lateral lamina 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 cornu 



(Cornu orale) is attached to the 



thyroid cornu of the hyoid bone; 



below it is a notch, which is con- 

 verted into a foramen (Foramen thy- 



reoideum) 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 chverges 



from its fellow to inclose a triangular 



space (Incisura thyreoidea caudalis), 



which is occupied by the crico-thyroid 



membrane. 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 l)y mucous membrane to a 



small (>xt(Mit. 



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



Thyroid notch 



^yiitg 



Anterior cornu 



Thyroid fora- 

 men 



Fig. 35L— Thvroid 



Cartil.\ge 

 View. 



Posterior cornu 

 Surface for articu- 

 lation with cricoid 



OF Horse, Ventral 



