Gallbladder and Biliary System Anatomy

Study Notes

The gallbladder is a pear-shaped or thumb-shaped organ located inferiorly to the liver.
The gallbladder is divided into the neck, body, and fundus.
The fundus is the anterior portion of the gallbladder.
The neck is the posterior portion, where Heister's Valve is located to prevent kinking.
The gallbladder measures 2.5-4 cm in the anteroposterior diameter and 7-10 cm in length.
The wall of the gallbladder is typically less than 3mm thick.
The gallbladder holds approximately 50 ml of bile.
The gallbladder's location can be identified using the following landmarks:
- The Main Lobar Fissure (MLF)
- The Portal Vein (PV)
- The Main Hepatic Vein (MHV)

Hartmann's Pouch: An outpouching near the neck of the gallbladder. It is a common location for stones to get stuck.
Phrygian Cap: A folding of the gallbladder fundus.
Junctional Fold: A fold at the neck of the gallbladder.
Partial or Full Septation: A potential for a double gallbladder.

The biliary duct system consists of two main portions:
- Intrahepatic
- Extrahepatic

Cystic Duct: Continuation of the gallbladder neck. Connects the neck of the gallbladder to the Common Hepatic Duct.
Common Hepatic Duct (CHD): Measures approximately 4 mm in diameter.
Common Bile Duct (CBD): Measures up to 6 mm in diameter. The diameter increases 1 mm for each decade of life.
The CBD passes through the head of the pancreas and joins with the pancreatic duct, forming the Ampulla of Vater.
The Ampulla of Vater enters the duodenum, controlled by the Sphincter of Oddi.

Outer Layer (Serosal)
Middle Layer (Fibromuscular): Aids in contraction.
Inner Layer (Mucosal): Contains rugal folds that aid in the secretion of mucus and the absorption of water.

Rokitansky-Aschoff Sinuses: Invasion of epithelium into the wall. These sinuses increase the surface area of the gallbladder wall, and stones can become lodged in them.

Transportation of Bile: The gallbladder transports bile produced by the liver to the intestine. It transports 1-2 liters of bile per day.
Concentration and Storage of Bile:
- The gallbladder concentrates and stores the bile.
- The bile is mostly composed of:
  - 82% Water
  - 12% Bile Acids
  - Bile is the principle route for excreting bilirubin and cholesterol.
  - Bile breaks down fats and aids in absorbing fatty acids.
Stimulated by Cholecystokinin (CCK)
- The gallbladder is stimulated to contract by CCK, which is released by the small intestine after a fatty meal.
Removal of the Gallbladder:
- Once the gallbladder is removed, the Sphincter of Oddi loses tonus (relaxation).
- This leads to increased pressure within the biliary system, resulting in bile flowing freely into the duodenum.
- Removal of the gallbladder results in dilation of the extrahepatic ducts.