INFERIOR VENA CAVA. 555 



Point of Termination. Occasionally the inferior vena cava joins the right azygos vein, which 

 is then of large size. In such cases, the superior cava receives the whole of the blood from the 

 body before transmitting it to the right auricle, except the blood from the hepatic veins, which 

 terminate directly in the right auricle. 



The lumbar veins, three or four in number on each side, collect the blood by 

 dorsal branches from the muscles and integument of the loins, and by abdomi- 

 nal branches from the walls of the abdomen, where they communicate with the 

 epigastric veins. At the spine, they receive branches from the spinal plexuses, 

 and then pass forwards round the sides of the bodies of the vertebrae beneath 

 the Psoas Magnus, and terminate at the back part of the inferior cava. The 

 left lumbar veins are longer than the right, and pass behind the aorta. The 

 lumbar veins communicate with each other by branches which pass in front 

 of the transverse processes. Occasionally two or more of these veins unite to 

 form a single trunk, the ascending lumbar, which serves to connect the com- 

 mon iliac, ilio-lumbar, lumbar, and azygos veins of the corresponding side 

 of the body. 



The spermatic veins emerge from the back of the testis, and receive branches 

 from the epididymis; they form a branched and convoluted plexus, called the 

 spermatic plexus (plexus pampiniformis), below the abdominal ring: the vessels 

 composing this plexus are very numerous, and ascend along the cord in front 

 of the vas deferens; having entered the abdomen, they coalesce to form two 

 branches, which ascend on the Psoas muscle, behind the peritoneum, lying one 

 on each side of the spermatic artery, and unite to form a single vessel, which 

 opens on the right side in the inferior vena cava, at an acute angle, on the left 

 side in the left renal vein, at a right angle. The spermatic veins are provided 

 with valves. The left spermatic vein passes behind the sigmoid flexure of the 

 colon, a part of the intestine in which fecal accumulation is common; this cir- 

 cumstance, as well as the indirect communication of the vessel with the inferior 

 vena cava, may serve to explain the more frequent occurrence of varicocele on 

 the left side. 



The ovarian veins are analogous to the spermatic in the male; they form a 

 plexus near the ovary, and in the broad ligament and Fallopian tube, commu- 

 nicating with the uterine plexus. They terminate as in the male. Valves are 

 occasionally found in these veins. These vessels, like the uterine veins, become 

 much enlarged during pregnancy. 



The renal veins are of large size, and placed in front of the renal arteries. 1 

 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 and 

 left inferior phrenic veins. It usually opens into the vena cava, a little higher 

 than the right. 



The suprarenal vein terminates, on the right side, in the vena cava; on the 

 left side, in the left renal or phrenic vein. 



The phrenic veins follow the course of the phrenic arteries. The two superior, 

 of small size, accompany the phrenic nerve and comes nervi phrenici artery; 

 the right terminating opposite the junction of the two venae innominate, the 

 left in the left superior intercostal or left internal mammary. The two inferior 

 phrenic veins follow the course of the phrenic arteries, and terminate, the right 

 in the inferior vena cava, the left in the left renal vein. 



The hepatic veins commence in the substance of the liver, in the capillary 

 terminations of the vena portas: these branches, gradually uniting, form three 

 large veins, which converge towards the posterior border of the liver, and open 

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

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



1 The student may observe that all veins above the Diaphragm, which do not lie on the same 

 plane as the arteries which they accompany, lie in front of them; and that all veins below the 

 Diaphragm, which do not lie on the same plane as the arteries which they accompany, lie behind 

 tham, except the renal and profunda femoris vein. 



