The bile duct is the name given to all parts of the body through which bile must pass during metabolism. A distinction is made between bile ducts located in the liver (intrahepatic bile ducts) and bile ducts located outside the liver (extrahepatic bile ducts). Bile is produced in the liver and then transported there via the bile ducts, conveyed to the intestine, and from there into the gallbladder.
What is the bile duct?
Schematic diagram showing the anatomy and structure of the gallbladder with gallstones. Click to enlarge. The bile duct is an important part of our digestive system. Through it, bile is delivered to specific locations in the body: either for direct digestion into the duodenum or for storage in the gallbladder (vesica fellea). Initially, bile is produced in the liver and then passes through the bile ducts into the intestines. Bile juice is a very viscous liquid that is usually a bright yellowish color. However, it can also turn greenish to brownish, especially if it has been thickened by storage in the gallbladder. Responsible for the coloration of the bile juice is the so-called bilirubin. Bile juice is absolutely necessary for the digestion of fats that are ingested with food. This breakdown of fats takes place in the duodenum, where all fats are broken down (emulsified) so that they can be further broken down by the pancreas and subsequently utilized or excreted.
Anatomy and structure
Many small bile ducts run through the liver. Bile produced there is transported through these bile ducts to the required sites. All the small bile ducts within the liver open into two bile ducts, the right hepatic bile duct and the left hepatic bile duct. In technical terms, these are called the right hepatic duct and the left hepatic duct. These two bile ducts in turn open at the hepatic orifice into a common bile duct known as the ductus hepaticus communis. Connected to the ductus hepaticus communis is another bile duct that leads directly to the gallbladder, called the ductus cysticus. The bile duct then runs through the head of the building salivary gland and merges with the excretory duct of the salivary gland. From there, both then continue into the duodenum.
Function and tasks
The bile duct with all its branches is responsible for the transport of bile and is thus a significant component of digestion in the human body. Bile is produced in the liver and must be transported from there to the required sites. If bile is needed for digestion, the liver produces the bile and the body transports the bile directly into the duodenum via the bile ducts. There, the bile breaks down all the ingested fats, which is the only way the fats can be further utilized by the pancreas. Excess bile that is not currently needed for digestion passes through a branch in the bile duct into the gallbladder. The gallbladder is thus the storehouse for unneeded bile. In addition, a concentration of bile takes place in the gallbladder, and the bile thickens in the process. If this bile is additionally needed for digestion, the gallbladder uses muscle contractions to excrete the bile into the bile duct, from where it is transported further into the duodenum. Without the bile duct, bile could not be transported to the specific locations to provide for smooth fat digestion. The pancreas would not be able to further break down the ingested fat.
Diseases and ailments
The bile duct, and also the production, storage and breakdown of bile, is often affected when diseases of the digestive system are present. It is not uncommon for a blockage of the bile ducts to occur, this condition is called cholestasis. It manifests itself in affected individuals primarily through an intolerance of fats. These are excreted in the stool because the body is no longer able to adequately digest fats. Such a disease can be caused by tumors. Gallstones are also a condition that affects the bile duct. Gallstones are caused by an imbalance in the production of bile, which contains too few soluble substances. This leads to the formation of crystals or stones in the bile. Often gallstones do not cause any symptoms.However, if they lead to a blockage or become trapped, this can lead to severe pain. This can also result in inflammation. All clinical pictures can lead to posthepatic jaundice (icterus). This results in yellowing of the skin, mucous membranes and conjunctiva of the eye. This disease should not be confused with conventional jaundice. The latter is virus-related and therefore has completely different causes. Icterus is also not an independent disease, but only a symptom.
