36 



TOPOGRAPHICAL ANATOMY OF THE 



left atria of the heart. After a short, oblique course in a dorsal 

 and caudal direction, the artery terminates by dividing into right 

 and left branches (one for each lung) that have already been 

 examined in connection with the roots of the lungs (page 20). 



Aorta. — The main systemic arterial trunk, the aorta,^ springs 

 from the left ventricle, its origin lying to the right of that of the 

 pulmonary artery and slightly caudal thereto. It is customary to 



Papillary muscle. 



Right ventricle. 



A. coronaria sinistra- 

 (ramus descendens) 



Papillary muscles. 



Transverse muscli 



-A. coronaria de 

 (ramus descend 



Left ventricle. 



Fig. 17. — Transverse section of the heart at the level indicated by the 

 line B in Fig- 15. 



consider the first part of the aorta as divisible into two portions : (1) the 

 ascending aorta (aorta ascendens), and (2) the aortic arch (arcus 

 aortse). In the horse, however, such a strict division is impracticable, 

 and it is sufficient to say that the ascending aorta is that part of a 

 continuous curved vessel from which the coronary arteries arise. 



Where it leaves the left ventricle the aorta is at its widest (bulbus 

 aortas), and here it is dilated into three pouch-like aortic sinuses 



1 doprrj (aorte) [Or.], from dapu (oeiro), I lift up. The term was first applied 

 to the bronchus, but later (Aristotle) it was used as in modern anatomy. 



I 



