VEINS 107 



THE PORTAL SYSTEM. 



The veins of the portal system collect the blood from the 

 digestive tract. They form a trunk, the vena portse, which 

 enters the liver and breaks up into small branches in its sub- 

 stance. The following veins form the portal system : 



Inferior mesenteric : drains rectum, pelvic, iliac, and 

 descending colon. It lies to the left of its artery, and passing 

 behind transverse part of the duodenum and the pancreas, 

 and over left kidney, opens into the splenic vein. (The 

 haemorrhoidal branches anastomose with the haemorrhoidal 

 branches of the internal iliac.) 



Superior mesenteric : drains small intestines, caecum, 

 ascending and descending colon. It passes upwards in front 

 and to right of superior mesenteric artery, in front of trans- 

 verse part of duodenum, and behind neck of pancreas joins 

 the splenic vein at the upper border of the pancreas to form 

 the portal vein. 



Splenic : commences in five or six tributaries in hilum of 

 spleen ; these unite to form a trunk which passes below 

 splenic artery from left to right, behind upper border of pan- 

 creas, and in front of aorta ; joins superior mesenteric at a 

 right angle. 



The gastric or coronary : a large vein accompanying coron- 

 ary artery from right to left along lesser curvature of stomach 

 to cardia, where it receives cesophageal tributaries, and, 

 passing to right behind lesser sac, opens into the vena portae. 



The vena portsa : is formed by the union of the splenic and 

 superior mesenteric veins in front of the right crus of dia- 

 phragm and inferior vena cava, and behind the neck of the 

 pancreas. Passes up behind first part of duodenum and then 

 between the layers of the small omentum, behind and between 

 the common bile-duct and hepatic artery, the duct being placed 

 on the right and artery on the left, to transverse fissure of liver ; 

 here it divides into right and left branches to corresponding 

 lobes, and also gives an offset to the Spigelian lobe. Con- 

 nected with the branch to the left lobe are in front the obliterated 

 umbilical vein and behind the ductus venosus, the remains of a 

 f jetal connection with the inferior vena cava. 



