portal-systemic anastomosis


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portal-systemic anastomosis

Any of the venous connections between the portal circulation and the main systemic circulation. These veins provide alternative routes by which venous blood normally shunted through the liver can reach the inferior vena cave and then the heart. Veins in the portal circulation have no valves; thus blood can travel backwards in the portal system if the pressure becomes greater than in the systemic system.
See also: anastomosis