Portal Venous Drainage

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  • Topic: Liver, Vein, Veins of the torso
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STUDENT’S DISCUSSION GUIDE

VENOUS DRAINAGE OF THE GASTROINTESTINAL TRACT
&
BILE DUCTS OF THE LIVER

Contributors:
dr. H. Andi Ansharullah, DAAK
dr. Arliek Rio Julia, MS
Safrina, Msi. Med

MEDICAL FACULTY
UNIVERSITY OF BRAWIJAYA
2010

VENOUS DRAINAGE OF THE GASTROINTESTINAL TRACT
The venous blood from the greater part of the gastrointestinal tract and its accessory organs drains to the liver by the portal venous system. The proximal tributaries drain directly into the portal vein, but the veins forming the distal tributaries correspond to the branches of the celiac artery and the superior and inferior mesenteric arteries. Portal vein

This important vein (fig. 2)drains blood from the abdominal part of the gastrointestinal tract from the lower third of the esophagus to halfway down the anal canal; it also drains blood from the spleen, pancreas, and the gallbladder. The portal vein enters the liver and breaks up into sinusoids, from which blood passes into the hepatic veins that join the inferior vena cava. The portal vein is about 2 inches (5 cm) long and is formed behind the neck of pancreas by the union of the superior mesenteric artery and splenic veins. It ascends to the right, behind the first part of the duodenum, and enters the lesser omentum. It then runs upward in front of the opening into the lesser sac to the porta hepatis, where it divides into left and right terminal branches. The portal circulation begins as a capillary plexus in the organs it drains and ends by emptying it blood into the sinusoids within the liver.

Figure 1 Tributaries of the portal vein.
Tributaries of the Portal Vein. The tributaries of the portal vein are the splenic vein, superior mesenteric vein, left gastric vein, right gastric vein, and cystic veins. 1. Spenic vein. This vein leaves the hilum of the spleen and passes to the right in the splenicorenal ligament lying below the splenic artery. It unites with the superior mesenteric vein behind the neck of the pancreas to form the portal vein (fig. 1). It receives the short gastric, left gastroepiploic, inferior mesenteric, and pancreatic veins. 2. Inferior mesenteric vein. The vein ascends on the posterior abdominal wall and joins the splenic vein behind the body of the pancreas (fig 1). It receives the superior rectal veins, the sigmoid veins, and the left colic vein. 3. Superior mesenteric vein. This vein ascends in the root of mesentery of the small intestine on the right side of the artery. It passes in front of the third part of duodenum and joins the splenic vein behind the neck of pancreas (fig. 1). It receives the jejuna, ileal, ileoclic, right colic, middle colic, inferior pancreaticoduodenal, and right gastroepiploic veins. 4. Left gastric vein. This vein drains the left portion of the lesser curvature of the stomach and the distal part of the esophagus. It opens directly into the portal vein (fig. 1) 5. Right gastric vein. This vein drains the right portion of the lesser curvature of the stomach and drains directly into the portal vein (fig. 1) 6. Cystic veins. These veins either drain the gallbladder directly into the liver or join the portal vein (fig. 1)

Figure 2 Portal systemic anastomoses: A, berween esophageal veins; B, between rectal veins; C, between the paraumbilical veins and small epigastric veins of the anterior abdominal wall; D, between colic veins and the retroperitoneal veins Portal-systemic anastomoses

Under normal conditions the portal venous blood traverses the liver and drains into the inferior vena cava of the systemic venous circulation by way of hepatic veins. This is the direct route. However, other, smaller communications exist between the portal and systemic systems, and they become important when the direct route becomes blocked (fig. 2) These communications are as follows:

1. At the lower third of the esophagus, the esophageal branches of the left gastric vein (portal tributary) anastomose with the...
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