Biliary Tract Functions and Impairment

Abstract

The biliary tract includes the entire biliary excretion route from the liver to the duodenum. Bile is secreted from hepatocytes into the bile canaliculi. It is eventually excreted into the duodenum after passing through the biliary tract. The main components of bile include bile acids, phospholipids, cholesterols, and bilirubin. Some of these substances are reabsorbed in the intestine and returned to the liver via the portal vein, a cycle termed enterohepatic circulation. Enterohepatic circulation involves physiologically active substances and ensures its effective use. The function of the biliary tract is controlled by the autonomic nervous system. Branches from the hepatic plexus, which is formed by the sympathetic nerves and the vagus nerve, are distributed across the biliary tract. The sphincter of Oddi at the papilla and gallbladder play important roles in the control of the bile efflux, and dysfunctions can occur when their motility is inhibited. The gallbladder dysfunction is a motility disorder and causes pain similar to chronic cholecystitis. The sphincter of Oddi regulates the excretion of bile and prevents the regurgitation of duodenal juice. In papillary dysfunction, the sphincter of Oddi is excessively contracted, which inhibits the excretion of bile and pancreatic juice. Pancreaticobiliary maljunction is a congenital malformation in which the pancreatic duct and the bile duct join outside the duodenal wall. In this condition, the sphincter of Oddi does not regulate the confluence of the pancreatic duct and bile duct, resulting in bidirectional regurgitation of bile and pancreatic juice and various complications in the bile duct and the pancreas.