The peribiliary portal system in the rabbit liver.

Arterial terminals and peribiliary plexuses in the rabbit liver were studied by the injection replica scanning electron microscope method. The branches of the hepatic artery are classified into three categories: (1) branches forming the peribiliary plexus, (2) terminal and some collateral branches which directly pour into the sinusoids at the periphery of the hepatic lobules, (3) branches which form poor capillary networks in the Glisson's sheath and finally join the peripheral sinusoids. The peribiliary plexus consists of two layers. The inner layer is a capillary network and the outer layer, a venous network. The efferent vessels arise from the venous network of the peribiliary plexus and have two different drainages: (1) into the adjacent hepatic sinusoids as the "lobular branches or routes" aud (2) into the interlobular veins as the "prelobular branches or routes." The former branches correspond to the "radicular portal veins" of KIERNAN (1833), and the latter to the "internal roots" of FERREIN (1749). Both routes deserve designation of peribiliary portal system. The plexus surrounding small bile ducts comprises a single layer of fine capillaries. Their connections with the hepatic sinusoids and the interlobular veins are quite the same as in the two-layered plexus. The pattern of the peribiliary drainage in the rabbit liver is similar to that in the rat liver (OHTANI and MURAKAMI, 1978). A possible significance of the peribiliary portal system as the transport route of hormones produced from the bile duct wall is discussed.