RIGHT AND LEFT CORONARY 



473 



su]>plyinff the structures between which it runs and the auricular sc])tuni; (6) a 

 preventricular branch (tiu;. o2()), which runs down the front of the right ventricle, 

 sup})lyhig its walls; [c) a right marginal branch (fig. o"26), Avhich courses down 

 the right margin of the right ventricle; (d) a posterior interventricular branch, 

 or the continuation of the coronary trunk, which passes down the posterior inter- 

 ventricular groove, giving twdgs to each ventricle and the interventricular septum, 

 and anastomosing at the apex of the heart with the anterior interventricular branch 

 of the left coronary artery; and (e) the transverse branch, which runs in the left 

 auriculo-ventricular groove to anastomose with the terminal branch of the left 

 coronary (fig. 32G). 



THE LEFT CORONARY ARTERY 



The left coronary artery (figs. 321 and 326), a little larger than the right, arises 

 from the left anterior sinus of Valsalva, and, passing forwards and to the left 

 between the pulmonary artery and left auricular appendix, courses round the heart 



Fig. 326. — Scheme of the Coroxary Arteries. (Walsham.) 



Posterior intervenlricular 

 branch of right coronary 

 artery 



AURICULAR APPENDAGE 



Right aiirifiilar hraiir/t 



Right coronary artery -J 



Preventricular branch 

 Right marginal branch 



Posterior interventricular 

 branch of right coronary 

 artery 



Transverse branch of right 

 coronary artery 



Terminal branch of left 

 coronary artery 



Left coronary artery 



A nterior interventricular 

 branch of left coronary 

 artery 



Left marginal branch 



in the left auriculo-ventricular groove to anastomose with the transverse bran(>h of 

 the right coronary artery. It gives ofif the following branches: (a) A left auricular 

 branch, which supplies the left auricle, the pulmonary artery, and the commence- 

 ment of the aorta, (h) A large anterior interventricular branch, Avhich is larger 

 than the continuation of the vessel between the auricle and ventricle, and is 

 regarded by some as the main trunk of the left coronary artery. It courses down- 

 wards in the anterior interventricular groove to the apex of the heart, where it 

 forms a slight anastomosis with the posterior interventricular branch of the right 

 vessel (fig. 324). It supplies both ventricles and the interventricular septum, (c) 

 A left marginal branch, which runs down the left margin of the heart, supplying 

 branches to the walls of the ventricle, {d) The terminal branch, the continuation 

 of the vessel, anastomoses with the transverse branch of the right coronary artery. 



Variations in the Coronary Arteries 



(a) They may arise as a common trunk, (b) They may both arise from the same sinus of 

 Valsalva, '(c) Tlie interventricular and terminal Ijranchos of tlie left coronary may arise 

 separately from the sinus of Valsalva. (d) One coronary artery may be larger than usual; 



