Corpus: Bile duct

The term bile ducts refers to all duct-like structures that channel the bile produced in the liver into the duodenum of domestic mammals via a branched drainage system.

The bile ducts can be divided into intrahepatic and extrahepatic ducts based on their location.

Intrahepatic bile ducts[Bearbeiten]

The bile produced in the liver cells (hepatocytes) drains into the interstitial biliary canaliculi (bile capillaries). In the peripheral areas of the individual hepatic lobules (lobulus hepatis), small bile ducts collect the accumulated bile and pass it on to the biliary interlobular ducts. As more and more smaller bile ducts merge to form larger duct systems, the biliary ducts are formed, which ultimately merge into a sinister hepatic duct and a dexter hepatic duct.

Extrahepatic bile ducts[Bearbeiten]

Both hepatic ducts merge differently depending on the species (with the exception of the dog) to form the common hepatic duct. This leaves the organ via the hepatic portal (Porta hepatis) to enter the hepatoduodenal ligament.

After the common hepatic duct has taken up the excretory duct of the gallbladder - the cystic duct - it is referred to as the choledochal duct. This opens on the papilla duodeni major into the initial section of the duodenum.

In domestic mammals, there are clear species-specific differences in the arrangement of the bile duct system.

Ruminants[Bearbeiten]

The simplest conditions are found in the largely unlobulated liver of cattle. Here the bile duct system corresponds to the general description given above: the biliary ducts of the lobus hepatis sinister, the lobus quadratus and the processus papillaris open into the ductus hepaticus sinister. The ductus hepaticus dexter receives the bile ducts from the lobus hepatis dexter and the processus caudatus.

Subsequently, the ductus hepaticus sinister and the ductus hepaticus dexter merge to form the ductus hepaticus communis, which merges into the ductus choledochus from the mouth of the ductus cysticus. In ruminants, there are additional ducts that open directly into the neck of the gallbladder as so-called hepatocystic ducts.

Horse[Bearbeiten]

In horses, the situation is generally just as clear. Here the bile ducts from the lobus hepatis sinister lateralis or lobus hepatis sinister medialis and the lobus quadratus open into the ductus hepaticus sinister. The corresponding bile ducts from the lobus hepatis dexter and lobus caudatus enter the ductus hepaticus dexter. Both large bile ducts merge to form the common hepatic duct.

As the horse has no gallbladder and consequently no cystic duct, the often dilated end section of the common hepatic duct is called the choledochal duct.

Pig[Bearbeiten]

In pigs, the bile ducts of the lobus hepatis sinister lateralis or lobus hepatis sinister medialis and from the lobus quadratus flow into the ductus hepaticus sinister. In contrast, the bile ducts from the lobus hepatis dexter lateralis and lobus hepatis dexter medialis as well as from the lobus caudatus remain largely isolated in order to flow individually into the ductus hepaticus communis. In this way, the formation of a ductus hepaticus dexter does not occur.

Dog[Bearbeiten]

The canine liver, which is equipped with deep interlobar incisures, exhibits a number of variations in the bile duct system. One common and at the same time clear possibility is explained below.

Approximately 3 to 5 bile ducts flow from each of the individual liver lobes into the particularly long cystic duct. From the last opening, this is known as the choledochal duct. A typical ductus hepaticus communis and its two-part inflow (ductus hepaticus sinister and ductus hepaticus dexter) is not formed in most cases in these animals.

Cat[Bearbeiten]

In the cat, the confluence of the hepatic ducts on both sides is just as varied. In most cases, between one and four hepatic ducts of different sizes flow into the cystic duct.

The common hepatic duct as well as the cystic duct and the choledochal duct show the typical three-layer structure:

• Tunica mucosa
• Tunica muscularis
• Tunica serosa

The choledochal duct is equipped with a high, single-layered prismatic epithelium interspersed with goblet cells in ruminants. In addition to mucous glands, there are also some serous glands, which are particularly numerous in cattle. In horses and pigs, however, these are found only sparsely.

• Nickel, Richard, August Schummer, Eugen Seiferle. Volume II: Organ systems. Parey, 2004.