Common bile duct

The common bile duct originates from the junction of the cystic duct (from the gallbladder) and the hepatic ducts (from the liver). Its primary function is to carry bile, which aids in the emulsification and absorption of dietary lipids, into the small intestine.

The duct typically passes through the hepatoduodenal ligament (in lesser omentum), coursing towards the duodenum, where it opens either independently or in conjunction with the pancreatic duct, at the major duodenal papilla.

Species-Specific Features

1. Dog (Canis familiaris)

• The common bile duct forms by the confluence of the hepatic ducts and the cystic duct.

• It usually joins with the major pancreatic duct before entering the duodenum at the major duodenal papilla.

• The terminal portion may have a hepatopancreatic ampulla (ampulla of Vater), and is often surrounded by a sphincter.

2. Cat (Felis catus)

• The common bile duct, pancreatic duct, and accessory pancreatic duct may all open at the major duodenal papilla, sometimes converging before entry.

• Cats have a relatively longer bile duct compared to dogs, and the cystic duct is well-defined.

3. Horse (Equus caballus)

• Horses lack a gallbladder, so there is no cystic duct.

• The bile duct is formed from multiple hepatic ducts that directly drain into the duodenum.

• Bile secretion is continuous due to the absence of storage in a gallbladder.

4. Ruminants (Cattle, Sheep, Goats)

• The bile duct is formed by the union of the cystic duct and common hepatic duct.

• Ruminants have a small or absent accessory pancreatic duct.

• The opening into the duodenum may be associated with a sphincter but generally lacks an ampulla.

5. Pig (Sus scrofa domestica)

• Pigs have a well-developed gallbladder and a common bile duct formed by the union of the hepatic and cystic ducts.

• The bile duct and pancreatic duct typically have separate openings into the duodenum.