An epithelial cell that is part of the bile duct. Cholangiocytes contribute to bile secretion via net release of bicarbonate and water. They are cuboidal epithelium in the small interlobular bile ducts, but become columnar and mucus secreting in larger bile ducts approaching the porta hepatis and the extrahepatic ducts. [ http://www.ncbi.nlm.nih.gov/pubmed/18356246 http://www.ncbi.nlm.nih.gov/pubmed/16550043 ]