Gallbladder

The gallbladder is a hollow, muscular organ situated in the liver's visceral surface and is responsible for storing and concentrating bile before releasing it into the duodenum.

The gallbladder consists of three main parts: the fundus (blind end), the body, and the neck, which continues into the cystic duct. Bile is carried to and from the gallbladder via the hepatic and cystic ducts, forming the common bile duct that opens into the duodenum. It is lined by mucosa with mucosal folds, and the wall has smooth muscle to allow bile expulsion during digestion.

2. Species-Specific Anatomy

• Dog (Canis lupus familiaris) The gallbladder is pear-shaped and lies between the right medial and quadrate lobes of the liver. The cystic duct joins with the hepatic ducts to form a relatively long bile duct, which empties into the duodenum at the major duodenal papilla, often in association with the pancreatic duct.

• Cat (Felis catus) Similar to the dog, but the gallbladder can be more variable in shape (e.g., bilobed). It lies in a fossa between the liver lobes. Cats have a well-developed bile duct and often a common opening for the bile and pancreatic ducts into the duodenum.

• Horse (Equus caballus) Horses do not have a gallbladder. Bile is continuously secreted from the liver into the duodenum. This anatomical adaptation is consistent with their continuous feeding behavior.

• Cattle (Bos taurus) The gallbladder is relatively large and elongated, with a distinct fundus that may protrude below the liver margin. It lies in a depression between the right lobe and the quadrate lobe. The cystic duct is long and joins with the hepatic ducts to form a bile duct that enters the duodenum independently of the pancreatic duct.

• Sheep and Goat (Ovis aries and Capra hircus) The gallbladder is relatively small and oval in shape. It is located similarly to that in cattle. The bile duct opens into the duodenum separately from the pancreatic duct.

• Pig (Sus scrofa domesticus) The gallbladder is elongated and curved, located in a depression between the right and quadrate lobes of the liver. The bile and pancreatic ducts usually open together into the duodenum via a common duct.