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Portal hypertension is a condition in which the blood pressure of the portal venous system is too high. It is often the result of cirrhosis of the liver. Liver cirrhosis can lead to increased intrahepatic vascular resistance and vasodilation of portal system arteries, both of which increase pressure in the portal vein. [4]
A liver segment is one of eight segments of the liver as described in the widely used Couinaud classification (named after Claude Couinaud) in the anatomy of the liver.This system divides the lobes of the liver into eight segments based on a transverse plane through the bifurcation of the main portal vein, [1] arranged in a clockwise manner starting from the caudate lobe.
It is a major component of the hepatic portal system, one of three portal venous systems in the human body; the others being the hypophyseal and renal portal systems. The portal vein is usually formed by the confluence of the superior mesenteric , splenic veins , inferior mesenteric , left , right gastric veins and the pancreatic vein .
The human hepatic portal system delivers about three-fourths of the blood going to the liver.The final common pathway for transport of venous blood from spleen, pancreas, gallbladder and the abdominal portion of the gastrointestinal tract [2] (with the exception of the inferior part of the anal canal and sigmoid colon) is through the hepatic portal vein.
In histology (microscopic anatomy), the lobules of liver, or hepatic lobules, are small divisions of the liver defined at the microscopic scale. The hepatic lobule is a building block of the liver tissue, consisting of a portal triad, hepatocytes arranged in linear cords between a capillary network, and a central vein.
hepatic portal vein (entering) The hepatic duct lies in front and to the right, the hepatic artery to the left, and the portal vein behind and between the duct and artery. It also transmits nerves and lymphatics. Sympathetic nerves - these provide afferent pain impulses from the liver and gall bladder to the brain.
A dilated portal vein (diameter of greater than 13 or 15 mm) is a sign of portal hypertension, with a sensitivity estimated at 12.5% or 40%. [18] On Doppler ultrasonography, a slow velocity of <16 cm/s in addition to dilatation in the main portal vein are diagnostic of portal hypertension. [19]
The right hepatic vein is the longest and largest of all the hepatic veins. It drains the liver segments VI and VII in their entirety, and variably participates in the drainage of segments V and VIII; the extent of drainage of the latter two segments by the right hepatic veins as opposed to the middle hepatic vein and possible variant accessory veins determines the calibre of the right hepatic ...