Gross anatomy of the liver, biliary tree, and pancreas in the black-tailed prairie dog (Cynomys ludovicianus).

The gross anatomy of the liver, extrapetatic biliary tree, sphincter of Oddi, and pancreas in the black-tailed prairie dog (Cynomys ludovicianus), a widely used animal model for investigations into biliary physiology, pathophysiology, and pathology, was studied in 10 animals. The liver consists of 4 lobes, the left lateral, median, right lateral, and caudate. The gallbladder lies on the ventral surface of the right lobule of the median lobe. The cystic and hepatic ducts unite to form the common bile duct which enters the duodenum approximately 5 mm distal to the pylorus. The lower end of the common duct dilates forming an ampulla which is surrounded proximally by a band of circular muscle fibres which constitute the choledochal sphincter. The pancreatic duct opens separately into the duodenum approximately 80 mm from the pylorus. Earlier physiologic studies have demonstrated that the choledochal sphincter has intrinsic motility distinct from the duodenum.