982 THE YASCULAE SYSTEM. 



right inferior phrenic vein, the right suprarenal vein, the right and left renal veins, the 

 right internal spermatic vein, and the right and left lumbar veins. 



Venae Hepaticae (Fig. 792). The hepatic veins convey blood which has 

 passed through the liver from the portal veins and from the hepatic artery, and 

 they open into that portion of the inferior vena cava which lies immediately below 

 the diaphragm, and behind the right lobe of the liver. They form two groups, an 

 upper group of two or three large trunks, and a lower group of smaller veins. 



The upper group occasionally consists of only two veins, a right and a left ; 

 more frequently there are three vessels, a right, a left, and a middle vein, and in 

 the latter case the middle vein issues from the caudate lobe (Spigelian). 



The veins of the lower group vary in number from six to twenty ; they return 

 blood from the right and caudate lobes. 



The hepatic veins commence in the interiors of the lobules of the liver as 

 central veins ; the central veins issue from the upper and posterior aspects of the 

 lobules, and unite together to form interlobular veins ; and the interlobular veins 

 unite with one another, as they converge towards the posterior surface of the liver, 

 to form the larger hepatic veins. 



Venae Phrenicae Inferiores. The inferior phrenic veins are formed by 

 tributaries which issue from the substance of the diaphragm. The right inferior 

 phrenic vein terminates in the upper part of the inferior vena cava. The left 

 vein passes posterior to the oesophagus, and usually terminates in the left supra- 

 renal vein. 



Venae Suprarenales. A single suprarenal vein issues from the hilum on the 

 anterior surface of each suprarenal gland ; the right vein terminates in the inferior 

 vena cava ; the left usually ends in the left renal vein, but sometimes it opens 

 directly into the inferior vena cava. 



Venae Renales. Each renal vein is formed by the union of five or six tribu- 

 taries which issue from the hiluin of the kidney, where they lie anterior to or are 

 intermingled with the corresponding arteries. 



The right renal vein is about 25 mm. (one inch long) ; it passes posterior to 

 the descending part of the duodenum, and terminates in the right side of the 

 inferior vena cava. 



The left renal vein is about 75 mm. long. It crosses anterior to the left psoas 

 major, the left crus of the diaphragm, and the aorta immediately below the superior 

 mesenteric artery. It lies behind the pancreas and the ascending part of the 

 duodenum, and, running above the transverse part of the duodenum, terminates in 

 the left side of the inferior vena cava. The left testicular or ovarian vein, accord- 

 ing to the sex, and almost invariably the left suprarenal vein, open into it. 



Venae Lumbales. There are usually four lumbar veins on each side, one 

 with each lumbar artery; the vein with the subcostal artery is not included 

 in this number. By their anterior and posterior branches the lumbar veins 

 drain the lateral and posterior walls of the abdomen. The anterior branches 

 commence in the lateral walls of the abdomen, where they communicate with the 

 superior and inferior epigastric veins. The posterior divisions issue from the 

 muscles of the back, in the lumbar region, and receive tributaries from the spinal 

 plexuses. The main stems pass forwards on the bodies of the vertebrae ; on each 

 side they run postero-medial to the psoas major muscle, whilst those of the 

 left side also pass posterior to the aorta. They terminate in the posterior part of 

 the inferior vena cava. Not uncommonly the corresponding veins of opposite sides 

 unite together to form a single trunk which enters the back of the inferior vena 

 cava. All the lumbar veins, of each side, are united together by a longitudinal 

 anastomosing vessel, the ascending lumbar vein. 



The Ascending Lumbar Vein. Each ascending lumbar vein passes upwards, 

 between the psoas major and the roots of the transverse processes of the lumbar 

 vertebrae. It commences in the lateral sacral vein of the same side, anastomoses 

 with the ilio-lumbar vein, connects the lumbar veins together, receives tributaries 

 from the anterior external vertebral plexus and anastomoses with the inferior vena 

 cava and the renal vein. The right ascending lumbar vein terminates in the 

 azygos and the left in the hemiazygos vein. 



