520 



RESPIRATORY SYSTEM OF THE HORSE 



The arytenoideous 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 

 raph^, which is connected with the transverse arytenoid ligament. Fibers of the 

 ventricularis muscle overlap its anterior part. It narrows the rima by draw- 

 ing the arytenoid cartilages together (adduction). 



The ventricularis^ lies in the lateral wall of the larynx, covered by the lamina of 

 the thjToid cartilage. It arises from the anterior part of the crico-thyroid membrane 

 and the ventral border of the thyroid lamina. Its fibers pass upward and backward 



Root of tongue 

 Soft palate (cut) 



Salpingo-pharyngeal 

 fold 



Epiglottis 



A ryteno-epiglottic 

 fold 



Wall of pharynx 



- — Arytenoid cartilage {apex) 



Posterior pillar of soft palate 



Position of cricoid 

 cartilage under oesophagus 



Thyroid gland 

 Trachea 

 (Esophagus 



Fig. 463. — Aditus Laryxgis of Hohse, Exposed by Opening Pharynx axd Beginning of CEsophagus Along 



Median Dorsal Line. 

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



to end partly on the processus muscularis, partly on the arytenoideus transversus, 

 meeting its fellow. 



The vocalis^ is also medial to the lamina of the "thyroid cartilage, and is in part 

 separated from the preceding muscle by the laryngeal saccule. It has an extensive 

 origin on the crico-thyroid membrane. Its direction corresponds with that of the 

 true vocal cord. It is inserted into the lateral surface of the arytenoid cartilage 

 below the processus muscularis. 



The two preceding muscles close the rima glottidis and slacken the vocal cords. 

 With the arytenoideus transversus and crico-arytenoideus lateralis they form a 

 sphincter which closes the entrance to the larynx. 



1 These two muscles were formerly taken together as parts of the thyro-arytenoideus muscle. 



