IXFERIOR VEXA CAVA 631 



these capillaries arise the licpatic veins Avliicli open into the inferior vena cava as 

 that vessel grooves the under surface of the liver. 



Of the other visceral veins, both renals, the right capsular, and the right 

 spermatic or ovarian open directly into the inferior vena cava; whilst the left 

 capsular and left spermatic or ovarian only join that vessel indirectly through the 

 left renal. 



Two of the superficial veins of the lower })art of the anterior abdominal wall, 

 the superficial epigastric and superficial circumflex iliac, enter the long saphenous 

 vein; and two of the deep veins from the like situation, the deep epigastric and 

 deep circumflex iliac, enter the external iliac vein. The blood in these vessels, 

 however, can flow upwards as well as in the normally downward direction. In 

 obstruction of the inferior vena cava they become greatly enlarged, and form, with 

 tlie superior epigastric vein and witli other superficial veins of the thorax with which 

 they anastomose, one of the chief (channels for the return of the ])lood from the 

 lower limbs. 



The veins of the pelvis, which receive the veins from tiie perin;eum and gluteal 

 regit)n, join the internal iliac vein. 



THE IXFERIOR VEXA CAVA 



The inferior or ascending vena cava (fig. 391 ) is the large vessel which 

 returns the blood from the lower extremities and the abdomen and pelvis. It is 

 formed by the confluence of the right and left connuon iliac veins oj)})osite the body 

 of the fifth lumbar vertebra, ascends in front of the lumbar verteln'ie to the right 

 of the abdominal aorta, passes through the caval opening in the diaphragm, and 

 ends in the lower and back part of the right auricle of the heart on a level with 

 the lower border of the ninth thoracic verteljra. At its origin it lies behind the 

 right common iliac arter}'' on a plane posterior to the aorta, but as it ascends it 

 ])asses slightly forward and to the right, getting on a plane anterior to the aorta, 

 and Ijecoming separated from that artery by the right crus of the diaphragm and 

 the lobulus Spigelii of the liver. Whilst in contact with the liver it lies in a deep 

 groove on the hinder surface of that organ, the groove being often converted into a 

 distinct canal by a thin portion of the hepatic substance bridging across the groove. 

 -Vs it passes through the diaphragm its Avails are attached to the tendinous margins 

 of the caval opening, and are thus held apart when the muscle contracts. On the 

 thoracic side of the diaphragm it lies for about half an inch within the pericar- 

 dium, the serous layer of that membrane l)eing reflected over it. 



Relations. — In front it is covered by the peritoneum, and crossed l)y the right 

 spermatic artery, branches of the aortic plexus of the sympathetic, the transverse 

 colon, the root of the mesentery, the duodenum, the head of the pancreas, the 

 portal vein, and the liver. The median group of the luml)ar lymphatic glands are 

 also in front of it below, and at its connnencement the right connuon iliac artery 

 rests U])on it. 



Behind, it lies on the luml)ar verteljrie, the right lumbar arteries, the right 

 renal artery, the right semilunar ganglion, and the right crus of the diaphragm. 



To the right are the peritoneum, liver, and psoas muscle. 



To the left is the aorta, and higher up the right crus of tlie diaphragm. 



Tributaries. — The inferior vena cava receives the following veins: — (1) the 

 renal veins: (2) the right suprarenal vein; (3) the right s])ermatic or (4) the right 

 ovarian vein; (5) the lumbar veins; (6) the inferior i)hrenic veins; (7) the 

 he])atic veins; and (S) the right and left common iliac veins. 



(1) The renal or emulgent veins r(>turn the blood from the kidneys. They 

 are short but thick trunks, and oiien into the vena cava nearly at right angles to 

 that vessel. The vein on the left side, like the kidney, is a little higher than on 

 the right, and is also longer, in consequence of its having to cross tlie aorta. The 

 comparative shortness of the right renal vein should be borne in mind in the 

 operation of nephrectomy, since, if too much traction is made on the ])edicle, not 

 only the vein, but a portion of the vena cava may be drawii into the ligature, as 

 shown in a specimen in J>t. Bartholomew's Hospital Museum. Each vein lies in 



