754 THE VASCULAR SYSTEMS 



The ovarian veins (vv. ovaricae) (Fig. 526) correspond with the spermatic in the 

 male: they form a plexus in the broad ligament near the ovary and about the 

 Fallopian tube, and communicate with the uterine plexus. They terminate Jii 

 the same way as the spermatic veins in the male. Valves are occasionally found 

 in these veins. Like the uterine veins, these vessels become greatly enlarged 

 during pregnancy. 



The renal veins (vv. renales] (Fig. 516) are of large size, and are placed in front 

 of the renal arteries. The left is longer than the right, and passes in front of the 

 aorta, just below the origin of the superior mesenteric artery. It receives the left 

 spermatic, the left inferior phrenic, and, generally, the left suprarenal veins. It 

 opens into the inferior vena cava a little higher than the right. 



The suprarenal veins (vv. suprarenales) (Fig. 515) are two in number; that on 

 the right side terminates in the inferior vena cava; that on the left side, in the left 

 renal or in the left phrenic vein. 



The inferior phrenic veins (vv. phrenicae inferiores) follow the course of the 

 phrenic arteries; the right ends in the inferior vena cava, the left in the left renal 

 vein. 



The hepatic veins (vv. hepaticae) commence in the substance of the liver, in the 

 capillary terminations of the portal vein and hepatic artery, intralobular veins; 

 these tributaries, gradually uniting into sublobular veins, usually form three large 

 hepatic veins, which converge toward the posterior surface of the liver and open 

 into the inferior vena cava, where that vessel is situated in the groove at the back 

 part of this organ. Of these three veins, one from the right and another from the 

 left lobe open obliquely into the inferior vena cava, that from the middle of the 

 organ and lobulus Spigelii having a straight course. The hepatic veins run singly, 

 and are in direct contact with the hepatic tissue. They are destitute of valves. 



THE PORTAL SYSTEM OF VEINS (Fig. 529). 



The portal system includes all the veins which drain the blood from the abdom- 

 inal part of the alimentary canal (with the exception of the lower part of the 

 rectum) and from the spleen, pancreas, and gall-bladder. From these viscera the 

 blood is conveyed to the liver by the portal vein. In the substance of the liver 

 the portal vein ramifies like an artery and terminates in the portal capillaries 

 (sinusoids^), from which the blood is conveyed to the inferior vena cava by the 

 hepatic veins. From this it will be seen that the blood of the portal system 

 passes through two sets of capillary vessels viz., (a) the capillaries of the alimen- 

 tary canal, spleen, pancreas, and gall-bladder; and (6) the portal capillaries in the 

 substance of the liver. The portal vein and its tributaries are destitute of valves. 



The portal vein (vena portae] is about three inches in length, and is formed 

 at the level of the second lumbar vertebra by the junction of the superior mesen- 

 teric and splenic veins, the union of these veins taking place in front of the inferior 

 vena cava and behind the neck of the pancreas. It passes upward behind the 

 first part of the duodenum and then ascends near the right border of the lesser 

 omentum to the right extremity of the transverse fissure of the liver, where it 

 divides into right and left branches, which accompany the corresponding branches 

 of the hepatic artery into the substance of the liver. In the lesser omentum it 

 is placed behind and between the common bile duct and the hepatic artery, the 

 former lying to the right of the latter. It is surrounded by the hepatic plexus 

 of nerves, and is accompanied by numerous lymphatic vessels and some lymph 

 nodes. The right branch of the portal vein enters the right lobe of the liver, 

 but before doing so generally receives the cystic vein. The left branch, longer 

 but of smaller caliber than the right, crosses the longitudinal fissure, gives branches 



