346 PULMONARY VKINS. 



receives in its course the gastric and pancreatic veins, and near its 

 termination the inferior mesenteric vein. 



The Gastric veins correspond with the gastric, gastro-epiploic, 

 and vasa brevia arteries, and terminate in the splenic vein. 



The VENA PORTJE, formed by the union of the splenic and supe- 

 rior mesenteric vein behind the pancreas, ascends through the right 

 border of the lesser omentum to the transverse fissure of the liver, 

 where it divides into two branches, one for each lateral lobe. In 

 the right border of the lesser omentum it is situated behind and be- 

 tween the hepatic artery and ductus communis choledochus, and is 

 surrounded by the hepatic plexus of nerves and lymphatics. At the 

 transverse fissure each primary branch divides into numerous 

 secondary branches which ramify through the portal canals, and 

 give off vaginal and interlobular veins, which terminate in the tabular 

 venous plexus of the lobules of the liver. The portal vein within 

 the liver receives the venous blood from the capillaries of the hepatic 



artery. 



* 



PULMONARY VEINS. 



The pulmonary veins, four in number, return the arterial blood 

 from the lungs to the left auricle of the heart ; they differ from the 

 veins in general, in the area of their cylinders, being very little larger 

 than the corresponding arteries, and in accompanying singly each 

 branch of the .pulmonary artery. They commence in the capilla- 

 ries upon the parietes of the bronchial cells, and unite to form a 

 single trunk for each lobe. The vein of the middle lobe of the right 

 lung unites with the superior vein so as to form the two trunks 

 which open into the left auricle. Sometimes they remain separate, 

 and then there are three pulmonary veins on the right side. The 

 right pulmonary veins pass behind the superior vena cava to the 

 left auricle, and the left behind the pulmonary artery ; they both 

 pierce the pericardium. Within the lung the branches of the pul- 

 monary veins are behind the bronchial tubes, and those of the pul- 

 monary artery in front ; but at the root of the lungs the veins are in 

 front, next the arteries, and then the bronchi. There are no valves 

 in the pulmonary veins. 



