Bile Flashcards
How much bile is produced per day?
500ml each day
What causes the yellow/green colour of bile?
Bilirubin and biliverdin
how much bile do hepatocytes secrete?
60% of bile
How much bile are cholangiocytes responsible for secreting?
40%
How is biliary excretion of bile salts and toxin performed?
Trough the use of biliary transporters on the apical and basolateral surfaces of hepatocytes and cholangiocytes
What is the BSEP and what is the purpose of it?
Bile Salt Excretory Pump - Involved int he active transport of bile acids into the bile
What transporters are MDR related proteins?
MRP1 and MRP2
What transports are the products of multi-drug resistance genes?
MDR1 and MDR3
What is MDR1 used to transport?
excretion of xenobiotics and cytotoxins
What are bile acids synthesized from?
Cholesterol
What are the two primary bile acids?
- Cholic acid
2. Chenodeoxycholic acid
What are the two secondary bile acids?
- Produced from cholic acid, is deoxycholic acid
2. Produced from chenodeoxycholic acid is lithocolic acid
What causes the conversion of primary bile acids into secondary bile acids?
Gut bacterial enzymes
What are bile acids conjugates with?
Glycine and taurine
What are the primary functions of bile acids?
reduce the surface tension of fats and emulsify fats prior to their digestion absorbtion
What is meant by the amphipathic nature of bile salts forming micelles?
They have hydrophobic domains on one surface and hydrophilic domains on the other surface
Describe the organisation of a micelles?
1x surface hydrophilic domains (hydroxyl & carboxyl) - faces OUT → dissolves in water
2nd surface hydrophobic domains (nucleus & methyl) faces IN → dissolves in fat
FFAs & cholesterol INSIDE
What happens to the sphincter of oddi between meals?
Sphincter of oddi is closed, and bile is diverted into the gal bladder for storage
What happens to the sphincter of Oddi during eating?
The sphincter of Oddi relaxes which allows the secretion of bile into the duodenum
What causes the gal bladder to contract?
- Gastic contents and acidic chyme enter into the duodenum and cause the release of CCK
- CCK binds to CCKa receptors and causes the gall bladder to contract, and release the stored bile into the intestine
What else aside from CCK causes the contraction of the gall bladder?
Ach from the parasympathetic fibres of the vagus nerves
What is the purpose of the gall bladder?
To store bile, concentrate it and acidify it
What are some of the main components of bile?
Water, bile acids, bilirubin, inorganic salts, cholesterol, fatty acids
Where is bilirubin produced from?
The breakdown of heme found in haemoglobin which is found in red blood cells