Cut through the left lobe of the liver and examine its internal structure . Two types of veins can be identified on the cut surface. Branches of the portal vein are always associated with branches of the hepatic artery and small bile ducts. Together these two types of blood vessels, and the bile duct are encircled by a fibrous sheath, and constitute a portal triad.
The portal vein and its branches convey blood to the sinusoids of the liver. The hepatic veins and its tributaries drain blood from the sinusoids into the inferior vena cava. The tributaries of the hepatic veins are not associated with the portal triad and course independently through the stroma of the liver.
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