446 



RESPIRATORY SYSTEM OF THE HORSE 



Its action is to dilate the rima glottidis by rotating the arytenoid cartilage so as to 

 cany the vocal process and cord outward. 



The crico-arytenoideus lateralis (M. crico-arytsenoideus lateralis) lies on the 

 inner face of the thyroid lamina. It arises from the anterior border of the lateral 

 part of the arch of the cricoid cartilage. The fibers pass in a dorsal direction and 

 converge on the processus muscularis of the arytenoid cartilage. It closes the 

 rima glottidis by rotating the arytenoid cartilage inward. 



The arytenoideus transversus (M. arytsenoideus transversus) is an unpaired 

 muscle which stretches across the concave dorsal surface of the arytenoid cartilages. 

 Its fibers are attached on either side to the processus muscularis and the ridge which 

 extends forward from it. The right and left parts of the muscle meet at a fibrous 



Root of tongue 

 Soft palate (cut) 



Salpingo-pharyngeal 

 fold 



Epiglottis 



Aryteno-epi glottic 

 fold 



Wall of pharynx 

 " Arytenoid cartilage {apex) 



Posterior pillar of soft palate 



(Esophagus (origin) 



Thyroid gland 

 K — Trachea 

 (Esophagus 



Fig. 355. — Aditus Laryngis of Horse, Exposed by Opening Pharynx and Beginning of QSsophagds Along 



Median Dorsal Line. 

 1, False vocal cord; S, lateral ventricle; 3, true vocal cords; 4, rima glottidis. 



raphe which is connected with the transverse arytenoid ligament. Fibers of the 

 thyro-arytenoideus muscle overlap its anterior part. It narrows the rima by 

 drawing the arytenoid cartilages together. 



The thyro-arytenoideus (Mm. ventricularis et vocalis) is situated in the lateral 

 wall of the larynx, covered by the lamina of the thyroid cartilage. It consists of 

 two parts, between which the mucous membrane of the lateral ventricle pouches to 

 form the saccule. The anterior part (M. ventricularis) arises from the anterior part 

 of the cricothyroid membrane and the ventral border of the thyroid lamina. Its 

 fibers pass upward and backward to end partly on the processus muscularis, partly 

 on the arytenoideus transversus, meeting its fellow. The posterior part (M. vocalis) 

 has a more extensive origin on the crico-thyroid membrane. Its direction corre- 



