THE CARDIAC VEINS. 621 



oesophageal opening, and then passes across the front of the spine from left to right 

 to end in the vena portae, at a point a little above the junction of the pyloric vein. 



The Portal Vein is formed by the junction of the superior rnesenteric and 

 splenic veins, their union taking place in front of the vena cava and behind the 

 upper border of the head of the pancreas. Passing upward through the right 

 border of the lesser omentum to the under surface of the liver, it enters the trans- 

 verse fissure, where it is somewhat enlarged, forming the sinus of the portal vein, 

 and divides into two branches which accompany the ramifications of the hepatic 

 artery and hepatic duct throughout the substance of the liver. Of these two 

 branches, the right is the larger, but the shorter, of the two. The portal vein is 

 about three or four inches in length, and, whilst contained in the lesser omentum, 

 lies behind and between the common bile duct and the hepatic artery, the former 

 being to the right, the latter to the left. These structures are accompanied by 

 filaments of the hepatic plexus of nerves and numerous lymphatics, surrounded by 

 a quantity of loose areolar tissue (capsule of Glisson), and placed between the 

 layers of the lesser omentum. 



The Cystic Vein. The vena portae generally receives the cystic vein, although 

 it sometimes terminates in the right branch of the vena portae. 



The portal vein divides, in the substance of the liver, like an artery, and its 

 minute ramifications end in capillaries, from which the blood is carried to the 

 inferior vena cava by the hepatic veins ; these veins also collect the blood which 

 has been brought to the liver by the hepatic artery. It will therefore be seen 

 that the blood which is carried to the liver by the portal vein passes through two 

 sets of capillary vessels, viz. : (1) the capillaries in the stomach, intestine, pancreas, 

 arid spleen, and (2) the capillaries of the portal vein in the liver. 



THE CARDIAC VEINS. 



The veins which return the blood from the substance of the heart are : the 



Great cardiac vein. Anterior cardiac veins. 



Posterior cardiac vein. Right or small coronary vein. 



Left cardiac veins. Coronary sinus. 



Venae Thebesii. 



The Great Cardiac Vein (sometimes called the Coronary vein) is a vessel of 

 considerable size, which commences at the apex of the heart, and ascends along 

 the anterior interventricular groove to the base of the ventricles. It then curves 

 to the left side, around the auriculo-ventricular groove, between the left auricle and 

 ventricle, to the back part of the heart, and opens into the left extremity of the 

 coronary sinus, its aperture being guarded by two valves. It receives, in its course, 

 tributaries from both ventricles, but especially the left, and also from the left 

 auricle ; one of these, ascending along the thick margin of the left ventricle, is of 

 considerable size. The vessels joining it are provided with valves. 



The Posterior Cardiac Vein (sometimes called the Middle cardiac vein) commences 

 by small tributaries, at the apex of the heart, communicating with those of the 

 preceding. It ascends along the posterior interventricular groove to the base of the 

 heart, and terminates in the coronary sinus, its orifice being guarded by a valve. 

 It receives the veins from the posterior surface of both ventricles. 



The Left Cardiac Veins are three or four small vessels, which collect the blood 

 from the posterior surface of the left ventricle, and open into the lower border of 

 the coronary sinus. 



The Anterior Cardiac Veins are three or four small vessels, which collect the 

 blood from the anterior surface of the right ventricle. One of these (the vein of 

 Graleri), larger than the rest, runs along the right border of the heart. They open 

 separately into the lower part of the right auricle. 



The Eight or Small Coronary Vein runs along the groove between the right 

 auricle and ventricle, to open into the right extremity of the coronary sinus. It 

 receives blood from the back part of the right auricle and ventricle. 



