Liver Excretion: Bile Production, Storage, and Function

Bile Synthesis and Flow

Hepatocytes continuously produce bile (500–1000 mL/day). Bile flows through canaliculi → bile ducts → common hepatic duct → either:

• Directly to duodenum via common bile duct (during meals).
• Diverted to gallbladder for concentration (water/electrolyte absorption) and storage (fasting).

Composition

• Bile salts (cholate, chenodeoxycholate) – emulsify fats.
• Phospholipids (lecithin) – stabilize micelles.
• Cholesterol.
• Bilirubin (waste from heme catabolism).
• Water, electrolytes.

Physiological Role

Bile salts emulsify dietary triglycerides → mixed micelles → pancreatic lipase access → fatty acid/monoglyceride absorption. Also excretory route for bilirubin, cholesterol, drugs, toxins.

Clinical Relevance

• Gallstones: cholesterol or pigment stones from supersaturation.
• Obstructive jaundice: blocked bile flow → conjugated hyperbilirubinemia.
• Bile acid malabsorption: chronic diarrhea.