Biliary tract and gallbladder

Intrahepatic bile ducts

The formation of the biliary system begins directly within the liver tissue. The secretion produced by hepatocytes initially enters microscopic bile canaliculi (canaliculi biliferi), which are located between the hepatic cells themselves.

Gradually increasing in size, the canaliculi pass into wider bile ductules (ductuli biliferi). Further, the secretion collects into interlobular bile ducts (ductus biliferi interlobulares), which in turn form large segmental ducts that collect bile from the corresponding liver segments.

Gallbladder anatomy

The gallbladder has a characteristic elongated shape, expanding at one end and tapering at the other. The organ features a dark green color and relatively thin walls. The length of the organ varies from 8 to 14 cm, and the width is 3–5 cm.

The structure of the organ comprises three main parts:

• Fundus — fundus vesicae biliaris (or felleae). This is the widest and most distal part of the organ, directed forward and toward the inferior border of the liver (in some cases, it may even project from beneath it).
• Body — corpus vesicae biliaris, representing the main, middle part of the reservoir.
• Neck — collum vesicae biliaris. This is the proximal, narrowest part, oriented toward the porta hepatis. It lies within the hepatoduodenal ligament and smoothly transitions into the cystic duct. At the junction of the body and the neck, an anatomical bend often forms, causing the neck to lie at an angle to the body.

Topographically, the organ is located on the visceral surface of the liver, in a special depression — the fossa for the gallbladder (fossa vesicae biliaris). This fossa serves as the border between the anterior division of the right lobe of the liver and its quadrate lobe. The surface of the gallbladder directly adjacent to the liver lacks a peritoneal covering and is fused with the fibrous capsule of the liver. The opposite, free side faces the abdominal cavity and is covered by the visceral peritoneum (sometimes intraperitoneal variants with an own mesentery occur).

Gallbladder wall

Except for the area closely adhering to the liver tissue, the organ wall consists of three classic membranes:

1. Serous coat (tunica serosa). Beneath it lies the loose subserous layer, which is particularly well-developed in extraperitoneal areas.
2. Muscular coat (tunica muscularis). It consists predominantly of a single circular layer of smooth muscle cells, although oblique and longitudinal bundles are also present. In the fundus region, this layer is less developed, whereas in the neck region, it is maximally thickened and continuously transitions into the musculature of the cystic duct.
3. Mucous membrane (tunica mucosa). It is quite thin and forms numerous folds (plicae mucosae), giving the inner surface a reticular relief. It is lined with a single-layered epithelium. In the neck, the mucosa forms a characteristic spiral fold (plica spiralis), and glands are located in its submucosa.

Extrahepatic bile ducts

This system transports bile outside the liver and includes three main ducts:

• Common hepatic duct (ductus hepaticus communis). It is formed in the porta hepatis by the union of the inconstant right and left hepatic ducts. Its length is 4–5 cm, and its diameter is 4–5 mm. The mucosa here is completely smooth, without folds.
• Cystic duct (ductus cysticus). It has a length of about 3 cm and a width of 3–4 mm. In the region of the neck, it makes two bends, then runs upward and to the right, joining the common hepatic duct at an acute angle. The muscular layer here is poorly developed (longitudinal and circular fibers are present), and the mucous membrane forms a spiral fold.
• Common bile duct (ductus choledochus). It is the direct continuation of the hepatic duct after it is joined by the cystic duct. It lies within the thickness of the hepatoduodenal ligament. The average length is 7–8 cm (can reach 12 cm). At a distance of 8–10 mm from its termination, its circular muscles thicken, forming the sphincter of the common bile duct (m. sphincter ductus choledochi).

Throughout all extrahepatic ducts, special mucous glands (glandulae mucosae ductulorum biliarium) are present in the submucosa.

Duodenal opening and blood supply

In its terminal part, the common bile duct unites with the pancreatic duct (ductus pancreaticus). Together they form a dilation — the hepatopancreatic ampulla (ampulla hepatopancreatica). This ampulla opens into the descending part of the duodenum at the apex of the so-called major duodenal papilla (papilla duodeni major).

In this zone lies a complex muscular apparatus — the sphincter of the hepatopancreatic ampulla (m. sphincter ampullae hepatopancreaticae). It functionally unites the musculature of the terminal parts of both ducts, regulating the fractional release of bile and pancreatic juice into the intestine.

Blood supply and innervation: Blood is supplied to the gallbladder via the cystic artery (a. cystica), which most commonly branches off the right hepatic artery. Venous blood drains into the portal vein system (v. portae hepatis). Neural regulation is provided by the hepatic plexus (plexus hepaticus), which includes fibers from the vagus nerves and the sympathetic trunk. Lymphatic drainage goes to the hepatic and cystic lymph nodes, and from there to the nodes of the celiac, gastric, pyloric, and pancreatoduodenal groups.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Topography of the hepatoduodenal ligament and its contents
• Variant anatomy of the confluence of the right and left hepatic ducts
• Structure and functions of the sphincter of Oddi (ampulla)
• Features of lymphatic drainage from the liver and biliary tract
• Secretory activity of hepatocytes and bile formation

Other topics in "Splanchnology / Digestive System"

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