THORACIC CAVITY 



The left coronary artery springs from the left posterior 

 aortic sinus (Fig. 38). It lies, at first, posterior to the pul- 

 monary artery, and runs towards the left for a short distance. 

 Then it turns forwards, between the pulmonary artery and 

 the auricle of the left atrium (Fig. 20), and divides into a 

 descending or interventricular, and a circumflex branch. 



Left 



pulmonary 

 artery 



Pulmonary artery 

 Interventricular 

 branch of left 

 coronary artery 

 Left posterior sinus 

 of aorta 

 Circumflex 

 branch of left 

 coronary artery 



Anterior cusp of 

 mitral valve 



Inferior cusp of 

 mitral valve 



Ligamentum arteriosum 



Pulmonary artery 

 Aorta 



Right pulmonary artery 

 Conus arteriosus 



Right coronary artery 



Right posterior sinus 

 of aorta 



Anterior cusp 

 of tricuspid valve 



Inferior cusp 

 Medial cusp 



Marginal branch 

 Interventricular branch of right coronary artery 



FIG. 38. The Base of the Ventricular Part of the Heart, from which the 

 Atria have been removed. The detached atria are depicted in Fig. 

 41. The specimen was hardened in situ. 



The interventricular branch passes downwards along the 

 sterno-costal surface of the heart, in the anterior longitudinal 

 sulcus (Fig. 39), and, after turning round the lower border of 

 the heart, in the cardiac notch, it anastomoses with the inter- 

 ventricular branch of the right coronary artery. The circum- 

 flex branch runs to the left, in the coronary sulcus, turns 

 round the left border of the heart (Fig. 38), and anasto- 

 moses, in the posterior part of the coronary sulcus, with the 

 transverse terminal branch of the right coronary artery. 



