THE VEINS OF THE HEART. 



509 



of the heart ; and secondly, those from which the blood is carried to the heart by 

 the inferior vena cava, viz., the veins of the lower limbs, the lower part of the trunk, 

 and the abdominal viscera. (For a general representation of the venous system, 

 see fig. 328, p. 376.) 



VEINS OF THE HEART. 



The greater number of the cardiac veins are collected into a large common trunk 

 which pours its blood into the lower part of the right auricle, in the angle between 

 the orifice of the inferior vena cava and the right auriculo-ventricular-orifice. The 

 terminal part of this trunk is somewhat dilated, and is named the coronary sinus. 

 The veins leading into the sinus are named the left or great, the posterior, the 

 middle, and the right or small cardiac veins. In addition to these, there are also 

 the anterior and the smallest cardiac veins, which open separately into the right 

 auricle. The veins of the heart are without valves, excepting at their terminations. 



The great cardiac or coronary vein commences near the apex of the heart, 

 and ascends, increasing gradually in size, along the anterior interventricular 



Fig. 399. THE HEART FROM BEHIND, TO SHOW THE 

 CARDIAC VEINS. (Allen Thomson.) ^ 



a, placed on the right auricle, points to the Eustachian valve 

 seen within the opening of the inferior vena cava ; b, left 

 auricle ; c, right ventricle ; d, left ventricle ; e, superior vena 

 cava ; /, arch of aorta ; 1, coronary sinus ; 2, great coronary 

 vein, turning round the heart in the left auriculo-ventricular 

 groove ; 3, posterior cardiac veins ; 4, middle cardiac vein ; 

 the small coronary vein is seen joining the right end of the 

 coronary sinus ; 5, one of the anterior cardiac veins passing 

 directly into the right auricle ; 6, the oblique vein, proceeding 

 downwards over the left auricle to join the coronary sinus. 



groove, in company with the anterior branch of 



the left coronary artery. It then turns backwards, 



by the side of the posterior branch of the same 



artery, in the groove between the left auricle and 



ventricle, and, having gained the posterior surface 



of the heart, terminates in the left end of the 



coronary sinus. In the first part of its course it 



receives branches from the interventricular septum and from the anterior wall of 



both ventricles ; and as it passes backwards it is joined by descending branches 



from the left auricle, and by ascending branches from the ventricle, one of 



which, lying along the left margin of the heart, is of considerable size. A valve, 



generally of two segments, is placed over the opening of the vein in the coronary sinus. 



The posterior cardiac veins are three or four in number, and ascend on the 

 posterior surface of the left ventricle to open into the coronary sinus along its lower 

 border. Sometimes one of these veins is much larger than the others. 



The middle cardiac vein, of considerable size, commences at the apex 

 of the heart, where it communicates with the radicles of the great coronary 

 vein, and passes upwards in the posterior interventricular groove to join the right 

 extremity of the coronary sinus. It receives branches from the interventricular 

 septum, and from the posterior wall of both ventricles, but more particularly the right. 



The right or small coronary vein collects blood from the hinder parts of 

 the right auricular and ventricular walls, and passes transversely in the groove 

 between the right auricle and ventricle to open into the right end of the coronary 

 sinus. This small vein is often represented by two or three separate branches, and 

 it is occasionally absent. 



