Biliary Tract and Gallbladder

Intrahepatic Biliary Tract

The formation of the biliary system begins directly within the liver tissue. Secretions produced by hepatocytes initially enter microscopic bile canaliculi (canaliculi biliferi), which lie between the individual liver cells.

Gradually widening, the canaliculi transition into broader bile ductules (ductuli biliferi). The secretion is then collected into interlobular bile ducts (ductus biliferi interlobulares), which in turn form larger segmental ducts collecting bile from respective liver segments.

Anatomy of the Gallbladder

The gallbladder has a characteristic elongated shape, widening at one end and tapering at the other. The organ is dark green with relatively thin walls. Its length ranges from 8 to 14 cm, and its width is 3–5 cm.

The organ consists of three main parts:

• Fundus — fundus vesicae biliaris (or felleae). This is the widest and most distal part of the organ, directed anteriorly and toward the inferior border of the liver (in some cases, it may project beyond it).
• Body — corpus vesicae biliaris, representing the main, central 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. An anatomical bend frequently forms where the body meets the neck, 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 dedicated depression — the fossa for the gallbladder (fossa vesicae biliaris). This fossa serves as the boundary 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 peritoneal cavity and is covered by visceral peritoneum (intraperitoneal variants with a dedicated mesentery also occur).

Gallbladder Wall

Except for the area tightly adhering to the liver parenchyma, the organ wall consists of three classic layers:

1. Serous coat (tunica serosa). Beneath it lies a loose subserous layer, which is particularly well-developed in extraperitoneal areas.
2. Muscular coat (tunica muscularis). Consists primarily of a single circular layer of smooth muscle cells, though oblique and longitudinal bundles are also present. This layer is less developed at the fundus and maximally thickened at the neck, where it 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 internal surface a reticular pattern. It is lined by a single-layered epithelium. In the neck, the mucosa forms a characteristic spiral fold (plica spiralis), and glands are located within its submucosa.

Extrahepatic Biliary Tract

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

• Common hepatic duct (ductus hepaticus communis). Formed in the porta hepatis by the union of the 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). About 3 cm long and 3–4 mm wide. 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 is weakly developed here (containing longitudinal and circular fibers), and the mucous membrane forms a spiral fold.
• Common bile duct (ductus choledochus). The direct continuation of the hepatic duct after receiving the cystic duct. It lies within the hepatoduodenal ligament. Average length is 7–8 cm (may reach 12 cm). At a distance of 8–10 mm from its termination, its circular muscle fibers thicken to form the sphincter of the common bile duct (m. sphincter ductus choledochi).

Special mucosal glands (glandulae mucosae ductulorum biliarium) are present in the submucosa throughout all extrahepatic ducts.

Duodenal Opening and Blood Supply

In its terminal part, the common bile duct merges with the pancreatic duct (ductus pancreaticus). Together, they form an expansion — the hepatopancreatic ampulla (ampulla hepatopancreatica). This ampulla opens into the descending part of the duodenum at the apex of the major duodenal papilla (papilla duodeni major).

This zone contains a complex muscular apparatus — the sphincter of the hepatopancreatic ampulla (m. sphincter ampullae hepatopancreaticae). It functionally combines the musculature of the terminal portions of both ducts, regulating the intermittent discharge of bile and pancreatic juice into the intestine.

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