Fig. 3. Zebrafish intrahepatic biliary development. (A-C) Tissue cross-sections of 60-hpf (A) and 70-hpf (B) embryos and a 80-hpf larva (C) processed for cytokeratin IHC. Nascent ducts (arrows) within the developing liver are evident at 60 hpf (A) and 70 hpf (B). By 80 hpf (C), a branching ductular network (arrows) is evident. Arrowheads in A,B indicate the origin of the extrahepatic duct. (D) Confocal projection of intrahepatic bile ducts in a 5-dpf larva processed for cytokeratin IHC. (E) Tissue section of a 70-hpf larva processed for P-glycoprotein IHC. Developing canaliculi (arrowheads) are evident between adjacent hepatocytes. (F) Confocal projection of hepatocyte canaliculi within the liver of a 5-dpf larva – note the elongated, tubular canalicular structure. (G,H) Confocal projection generated from contiguous Z-sections of a 75-hpf larva (G) and a 5-dpf larva (H) processed for cytokeratin IHC. Intrahepatic bile ducts emerge from the liver to form the common hepatic duct (chd), and join the cystic duct (cd) and common bile duct (cbd) that inserts into the intestine (i). (I) Transmission electron micrograph of a 70-hpf larva, showing a developing canaliculus (c) near the hepatocyte nucleus (hn). (J) Canaliculus of a 70-hpf larva anastomosing with a bile duct composed of two ductular cells (dc). (K,L) Transmission electron micrograph from a 5-dpf larva, showing a ductular cell within a hepatocyte tubule anastomosing with several canaliculi from surrounding hepatocytes (K). (L) Distal portion of a bile duct within the center of a hepatocyte tubule. Electron-dense particles within bile are evident in the duct lumen. e, esophagus; g, gall bladder; l, liver; pa, pancreas; p, pronephric duct.