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Portal vein

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Title: Portal vein  
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Subject: Duodenum, Fistula, Cystic duct, Embolization, Common hepatic duct, Banti's syndrome, Falciform ligament, Hepatic portal system, Vitelline veins, Round ligament of liver
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Portal vein

Vein: Hepatic portal vein
The portal vein and its tributaries. It is formed by the superior mesenteric vein and splenic vein. Lienal vein is an old term for splenic vein.
Latin vena portae hepatis
Gray's subject #174 681
Drains from    Gastrointestinal tract, spleen, pancreas
Source splenic vein, superior mesenteric vein
Drains to liver sinusoid
MeSH Portal+Vein
This page is the redirect for portal vein. For a vein that connects two systems of capillary beds see portal venous system.

The hepatic portal vein is a blood vessel that conducts blood from the gastrointestinal tract and spleen to the liver. This blood is rich in nutrients that have been extracted from food, and the liver processes these nutrients; it also filters toxins that may have been ingested with the food. The liver receives about 75% of its blood through the hepatic portal vein, with the remainder coming from the hepatic artery proper. The blood leaves the liver to the heart in the hepatic veins.

The hepatic portal vein is not a true vein, because it conducts blood to capillary beds in the liver and not directly to the heart. It is a major component of the hepatic portal system, one of only two portal venous systems in the body – with the hypophyseal portal system being the other.

The hepatic portal vein is usually formed by the confluence of the superior mesenteric and splenic veins and also receives blood from the inferior mesenteric, gastric, and cystic veins.

Conditions involving the hepatic portal vein cause considerable illness and death. An important example of such a condition is elevated blood pressure in the hepatic portal vein. This condition, called portal hypertension, is a major complication of cirrhosis.


Anatomy

Tributaries of the hepatic portal vein[1]

Measuring approximately 8 cm (3 inches) in adults,[2] the hepatic portal vein is located in the right upper quadrant of the abdomen, originating behind the neck of the pancreas.[3]

In most individuals, the hepatic portal vein is formed by the union of the superior mesenteric vein and the splenic vein.[4] For this reason, the hepatic portal vein is occasionally called the splenic-mesenteric confluence.[3] Occasionally, the hepatic portal vein also directly communicates with the inferior mesenteric vein, although this is highly variable. Other tributaries of the hepatic portal vein include the cystic and gastric veins.[1]

Immediately before reaching the liver, the portal vein divides into right and left. It ramifies further, forming smaller venous branches and ultimately portal venules. Each portal venule courses alongside a hepatic arteriole and the two vessels form the vascular components of the portal triad. These vessels ultimately empty into the hepatic sinusoids to supply blood to the liver.[1]

Portacaval anastomoses

The portal venous system has several anastomoses with the systemic venous system. In cases of portal hypertension these anastamoses may become engorged, dilated, or varicosed and subsequently rupture.

Accessory hepatic portal veins

Accessory hepatic portal veins are those veins that drain directly into the liver without joining the hepatic portal vein. These include the paraumbilical veins as well as veins of the lesser omentum, falciform ligament, and those draining the gallbladder wall.[3]

Physiology

The hepatic portal vein and hepatic arteries form the liver's dual blood supply. Approximately 75% of hepatic blood flow is derived from the hepatic portal vein, while the remainder is from the hepatic arteries.[3]

Unlike most veins, the hepatic portal vein does not drain into the heart. Rather, it is part of a portal venous system that delivers venous blood into another capillary system, namely the hepatic sinusoids of the liver. In carrying venous blood from the gastrointestinal tract to the liver, the hepatic portal vein accomplishes two tasks; namely, it supplies the liver with metabolic substrates and it ensures that substances ingested are first processed by the liver before reaching the systemic circulation. This accomplishes two things. First, possible toxins that may be ingested can be detoxified by the hepatocytes before they are released into the systemic circulation. Second, the liver is the first organ to absorb nutrients just taken in by the intestines. After draining into the liver sinusoids, blood from the liver is drained by the hepatic vein.

Role in disease

Portal hypertension

Main article: Portal hypertension

Increased blood pressure in the portal vein, called portal hypertension, is a major complication of liver disease, most commonly cirrhosis.[5] Stigmata of portal hypertension include those of chronic liver disease: ascites, esophageal varices, spider nevi, caput medusae, and palmar erythema.[6]

Pylephlebitis

Main article: Pylephlebitis

Pylephlebitis is infection of the hepatic portal vein, usually arising from an infectious intraabdominal process such as diverticulosis.[7][8]

References

Additional images

External links

  • 38:12-0109 - "Stomach, Spleen and Liver: The Visceral Surface of the Liver"
  • 7959
  • 8565
  • 8697
  • pembody/body8a
  • figures/chapter_30/30-2.HTM
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