Regulatory mechanisms of hepatic microcirculatory hemodynamics: hepatic arterial system.

This article reviews authors' recent studies on hepatic microcirculation with special reference to hepatic arterial system. It is concluded that: (1) Hepatic arterial blood pours into the hepatic sinusoid indirectly via the anastomosis between the terminal hepatic arteriole (THAo) and the portal venule (PVn), and directly through the THAo or the capillaries derived from the arterial capillary network around the bile duct in the portal tract; (2) The steep blood pressure gradient between the THAo and the sinusoid is considered to be maintained not only by the relaxation and contraction of the "precapillary sphincter" at the end of the THAo, but also by the coordinated dilatation and contraction of two types of sinusoidal endothelial fenestrae (SEF) particularly around the portal tract (zone 1); (3) In the regulation of hepatic sinusoidal microcirculation, the hepatic arterial system may supplementarily provides a driving force to the sinusoidal blood flow for keeping it smooth and constant. The main regulators of the sinusoidal blood flow would be present in the portal venous system. The hepatic artery is essential for supplying oxygen to the sinusoidal blood as well as to the bile ducts, portal venules and nerves in the portal tract.