Biliary secretion and enterohepatic secretion of bile salts Flashcards
What is bile
Complex lipid-rich micellar solution (water, inorganic electrolytes and organic solutes. Bile acids - phospholipids, cholesterol, bilirubin)
Where are bile acids synthesised?
From cholesterol in pericentral hepatocytes of acini
Break down of cholesterol into 2 acids - what are these primary bile acids called?
Cholic acid and chenodeoxycholic acid.
They are conjugated before secretion into the bile (to trap in lumen)
Intestinal bacteria break down primary bile acids into secondary bile acids - what are the 2 called?
Deoxycholic acid and lithocholic acid
Describe polarity of bile acids
Amphipathic - both hydrophilic and hydrophobic parts.
What does emulsification do?
Increases surface area for lipolysis by lipase.
What amphipathic protein allows lipase close enough to the emulsion droplet?
Colipase
How can the monoglycerides, fatty acids and bile salts diffuse across into the enterocyte?
Through aqueous channels because bile salts are amphipathic
What helps induce bile flow?
Bile acids due to the osmotic effect.
What does CCK do?
Stimulates opening of sphincter of Oddi and contraction of gallbladder, open allowing bile to flow into intestine.
Journey of bile
Made in liver, stored in gallbladder, food =flow out of gallbladder, into duodenum (breaks fat down to small globules). Reabsorbed into blood in the ileum. Bile recycled 2-3 times per meal!
Negative feedback loop for bile acid formation.
When bile acid in ileum, more FGF19 (endocrine polypeptide hormone) produced, inhibits enzyme that converts cholesterol into cholic acid.
