Anatomy: The biliary system is divided into two major systems, intrahepatic and extrahepatic, including the intrahepatic and extrahepatic bile ducts, the gallbladder, and the sphincter of Oddi. The biliary system starts from the intrahepatic capillary bile ducts and opens at the duodenal papilla. 1.Intrahepatic bile duct: It starts from intrahepatic capillaries and converges into interlobular bile duct, hepatic segment, hepatic lobe bile duct and intrahepatic left and right hepatic ducts step by step. Its path is basically the same as that of intrahepatic artery and portal vein branches, and all three are wrapped by a connective tissue sheath. 2.Extrahepatic bile duct: It consists of extrahepatic left and right hepatic ducts and common hepatic duct, gallbladder, common bile duct, etc. (1) Hepatic duct and common hepatic duct: the extrahepatic left hepatic duct is longer, about 0.2-3Cm, and is located in the transverse groove of the hepatic portal; the right hepatic duct is shorter, about 0.2Cm; the diameter of the hepatic duct is about 0.3cm. The left and right hepatic ducts converge slightly below the hepatic portal to form the common hepatic duct, which travels down along the right anterior edge of the hepatoduodenal ligament and converges with the bile cyst duct. In adults, the common hepatic duct is about 2-4 Cm long and 0.5 Cm in diameter. hepatic ducts often have variants and commonly have paracolic ducts, which are prone to surgical malpractice. (2) Gallbladder and cystic duct: attached to the visceral surface of the liver, equivalent to the anterior edge of the left and right hepatic junction midline, pear-shaped, about 8cm × 3cm in size, can store 40-60ml of bile. the gallbladder is divided into three parts: base, body and neck, the neck is enlarged in the shape of a pouch, called Hartmann’s pouch, where gallbladder stones are often harbored. The cystic duct is about 2-3 cm long and 0.3 Cm in diameter, and the inner wall of the cystic duct is flat and smooth near the common hepatic duct, while the inner wall of the cystic neck has spiral mucosal folds, called Hartmann’s flap, which is an internal scaffold to prevent the cystic duct from twisting and has the function of regulating the flow of bile in and out of the gallbladder. The triangle of the gallbladder (Ca1ot triangle) is a triangle formed by the cystic duct, the common hepatic duct and the inferior hepatic margin. The gallbladder artery, the right hepatic artery and the paramedian right hepatic duct penetrate in this area, which is a dangerous area where biliary surgery is highly prone to miscarriage. (3) Common bile duct: The common hepatic duct and the cystic duct converge to form the common bile duct, which is about 7-9 Cm long and 0.6-0.8 Cm in diameter. according to its travel and adjacency, the common bile duct is divided into four segments, the upper duodenal segment, the posterior duodenal segment, the pancreatic segment, and the inner duodenal wall segment. In about 80-90% of individuals, the common bile duct and the main pancreatic duct converge in the duodenal wall to form a common channel and expand to form a biliopancreatic pot belly surrounded by the sphincter of Oddi, which opens into the duodenal papilla. The sphincter of Oddi has the role of controlling the area and regulating the discharge of bile and pancreatic juice, as well as preventing the reflux of duodenal contents. Physiological functions of the biliary system: The main physiological function of the biliary system is to transport and regulate the bile secreted by the liver into the duodenum (the function of secretion, storage, concentration and transport of bile). Bile is secreted by hepatocytes and bile ducts, with a daily secretion of about 800~1200ml per day, 3/4 of which is secreted by hepatocytes. 97% of bile is water, other major components are bile acid salts, cholesterol, lecithin, bile pigments, fatty acids and inorganic salts, etc., with a specific gravity of 1.011 and pH 6.0~8.8. The functions of bile are excretion of various hepatic metabolites; emulsification of fat, activation and stimulation of The function of bile is to excrete various hepatic metabolites, emulsify fat, activate and stimulate the secretion of pancreatic lipase, hydrolyze and absorb lipids in food, promote the absorption of cholesterol and various fat-soluble vitamins, neutralize gastric acid, stimulate intestinal peristalsis, and inhibit the growth and reproduction of pathogenic bacteria in the intestine. The secretion of bile is regulated by neuroendocrine regulation. When the vagus nerve is excited, bile secretion increases; when the sympathetic nerve is excited, bile secretion decreases. The gallbladder plays the role of concentrating, storing and discharging bile through absorption, secretion and movement. The mucous membrane of gallbladder has a strong function of absorbing water and electrolytes from bile, which can absorb about 90% of water in bile, concentrate it 5-10 times and store it in gallbladder. Bile secretion is continuous, but its discharge is regulated by neurological and humoral factors (gastrointestinal hormones and metabolites, etc.) through contraction of the smooth muscle of the gallbladder and relaxation of the sphincter of Oddi, and is intermittent with or without food. The duration and amount of bile discharge is related to the type and amount of food consumed. When the gallbladder is inflamed for a long time or the sphincter of Oddi is dysfunctional, the bile discharge is impaired and the bile is stagnant, which can easily cause solids to be analyzed and formed into stones. The mucous membrane of gallbladder secretes about 20ml of mucous substance every day, and the main component is mucin, which has the function of protecting and lubricating the mucous membrane of gallbladder. When the gallbladder duct is completely blocked but not co-infected, the bilirubin suit in the bile is absorbed and the mucus secreted by the gallbladder mucosa accumulates in the gallbladder and becomes a colorless and transparent liquid called white bile. At this time, the gallbladder is called hydronephrosis. If the gallbladder is removed, the common bile duct can be compensated with dilation, thickening of the duct wall and hypertrophy and hyperplasia of the mucosal glands, so that the bile can be concentrated to a certain extent when it passes through the bile duct system. Special tests and care for biliary tract diseases Ultrasound is preferred