Anatomy and vascular biology of the cells in the portal circulation

Portal hypertension occurring during the natural course of liver cirrhosis is a consequence of the increased intrahepatic resistance to portal flow. For a long time, this phenomenon has been ascribed only to the profound changes of liver tissue angioarchitecture consequent to the progression of the fibrogenic process. However, studies performed during the last decade have demonstrated that there is also an increased vascular tone that could be modulated to a certain extent by pharmacological agents. The aim of this chapter is to provide general information on the anatomy of the portal systems and on the regulation of vascular tone in this specific vascular district and in the splanchnic circulation. Information about the collateral circulation that becomes relevant in the case of portal hypertension is also provided.