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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. 75% of total liver blood flow is 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. ==Structure== Measuring approximately 8 cm (3 inches) in adults, the hepatic portal vein is located in the right upper quadrant of the abdomen, originating behind the neck of the pancreas.〔 In most individuals, the hepatic portal vein is formed by the union of the superior mesenteric vein and the splenic vein. For this reason, the hepatic portal vein is occasionally called the ''splenic-mesenteric confluence''. 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.〔 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.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hepatic portal vein」の詳細全文を読む スポンサード リンク
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