Convoluted bile ducts in the liver of the larval lamprey, Petromyzon marinus L

Summary The three-dimensional structure of the bile ducts and their relationship to the blood vessels were studied in the larval lamprey by scanning electron microscopy of the intact tissue and of biliary and vascular casts. The intrahepatic gall bladder is situated in the cephalic portion of the liver and a cystic duct is connected to a straight intrahepatic common bile duct, which extends to the extrahepatic bile duct at the caudal end of the liver. Several smaller intrahepatic common bile ducts are connected directly to the intrahepatic common bile duct, are convoluted or serpiginous and are surrounded intimately by sinusoids. This arrangement enables the bile ducts to have increased surface area exposed to blood vessels. The functional significance of this arrangement is discussed with respect to the modification of bile through the transport of solutes and the similarity of this bilio-vascular relationship to the peribiliary vascular plexus of the mammalian liver.