The isolated artery: An intrahepatic arterial pathway that can bypass the lobular parenchyma in mammalian livers

Controversy persists concerning the distribution of intrahepatic arterial t ermination. Apart from nourishing structures in the portal tract, several a uthors have suggested arterial supply to some isolated vascular beds that b ypass the parenchyma, but this was not verified morphologically. In the pre sent study, the existence of an isolated hepatic artery unaccompanied by a portal vein or a bile duct was shown in livers of pigs and other mammals in cluding the dog, seal, ox, horse, and man. After colored media injection, l iver blocks were sampled near the hepatic capsule and hepatic vein and subj ect to histologic assessment. The hepatic artery dissociated from superfici al portal tract, ramified, and anastomosed extensively, forming a capsular plexus that drained at places into peripheral sinusoids in which resistive structural elaborations were observed. The artery also dissociated and fed an intramural plexus (vasa vasorum) of hepatic veins. This was collected in to a vessel that penetrated the intima into the vein's lumen. In smaller su blobular veins, the plexus emptied into adjacent sinusoids; in central vein s, the plexus was poorly developed. In canine and phocine livers, which hav e a special throttling musculature in sublobular veins, the isolated arteri oles were numerous; in bovine and equine livers, which have a thick fibrous investment, the capsular plexus was well-developed. Occurrence of the isol ated artery also was confirmed in the human but not in the rodent liver. In conclusion, the isolated artery is responsible for isolated vascular beds, in which the transintimal pathway can bypass the lobular sinusoids.