Bile

Bile is a yellow-green alkaline liquid secreted by the liver into the right and left hepatic ducts and then into the common hepatic duct. From here, it can take two paths.

The bile can enter the cystic duct, leading to the gallbladder, or it can flow into the bile duct, converging at the sphincter of Oddi at the duodenum.

When the sphincter is closed, bile is returned to the gallbladder, where it is stored and concentrated until needed.

When dietary fats reach the duodenum, the gallbladder contracts and the sphincter of Oddi opens, releasing bile into the duodenum.

Here, the bile salts emulsify the dietary lipids by forming micelles, aiding in lipid digestion and absorption.

Additionally, the alkalinity of bile neutralizes excess stomach acid in the chyme. 

In addition to electrolytes, triglycerides, and phospholipids, bile also contains bilirubin, a yellow pigment formed as a byproduct of hemoglobin breakdown in dying RBCs.

Bilirubin is metabolized by the colonic bacteria, producing urobilinogen and stercobilinogen, giving feces its brown color.