Biliary anatomy. Common variants:TrifurcationRight anterior or posterior hepatic duct branches from common duct Cystic duct is variable in its course, may join right hepatic duct. Biliary anatomy. Biliary anatomy. Cystic artery is usually a branch of the R hepatic. Biliary histology. Layers of gallbladder:Epithelium (columnar)Lamina propriaSmooth muscleSubserosal connective tissueSerosaNo submucosa or muscularis mucosa!.