Bile

Question 1

How much bile is produced per day?

Answer 1

500ml each day

Question 2

What causes the yellow/green colour of bile?

Answer 2

Bilirubin and biliverdin

Question 3

how much bile do hepatocytes secrete?

Answer 3

60% of bile

Question 4

How much bile are cholangiocytes responsible for secreting?

Answer 4

40%

Question 5

How is biliary excretion of bile salts and toxin performed?

Answer 5

Trough the use of biliary transporters on the apical and basolateral surfaces of hepatocytes and cholangiocytes

Question 6

What is the BSEP and what is the purpose of it?

Answer 6

Bile Salt Excretory Pump - Involved int he active transport of bile acids into the bile

Question 7

What transporters are MDR related proteins?

Answer 7

MRP1 and MRP2

Question 8

What transports are the products of multi-drug resistance genes?

Answer 8

MDR1 and MDR3

Question 9

What is MDR1 used to transport?

Answer 9

excretion of xenobiotics and cytotoxins

Question 10

What are bile acids synthesized from?

Answer 10

Cholesterol

Question 11

What are the two primary bile acids?

Answer 11

1. Cholic acid

2. Chenodeoxycholic acid

Question 12

What are the two secondary bile acids?

Answer 12

1. Produced from cholic acid, is deoxycholic acid

2. Produced from chenodeoxycholic acid is lithocolic acid

Question 13

What causes the conversion of primary bile acids into secondary bile acids?

Answer 13

Gut bacterial enzymes

Question 14

What are bile acids conjugates with?

Answer 14

Glycine and taurine

Question 15

What are the primary functions of bile acids?

Answer 15

reduce the surface tension of fats and emulsify fats prior to their digestion absorbtion

Question 16

What is meant by the amphipathic nature of bile salts forming micelles?

Answer 16

They have hydrophobic domains on one surface and hydrophilic domains on the other surface

Question 17

Describe the organisation of a micelles?

Answer 17

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

Question 18

What happens to the sphincter of oddi between meals?

Answer 18

Sphincter of oddi is closed, and bile is diverted into the gal bladder for storage

Question 19

What happens to the sphincter of Oddi during eating?

Answer 19

The sphincter of Oddi relaxes which allows the secretion of bile into the duodenum

Question 20

What causes the gal bladder to contract?

Answer 20

1. Gastic contents and acidic chyme enter into the duodenum and cause the release of CCK
2. CCK binds to CCKa receptors and causes the gall bladder to contract, and release the stored bile into the intestine

Question 21

What else aside from CCK causes the contraction of the gall bladder?

Answer 21

Ach from the parasympathetic fibres of the vagus nerves

Question 22

What is the purpose of the gall bladder?

Answer 22

To store bile, concentrate it and acidify it

Question 23

What are some of the main components of bile?

Answer 23

Water, bile acids, bilirubin, inorganic salts, cholesterol, fatty acids

Question 24

Where is bilirubin produced from?

Answer 24

The breakdown of heme found in haemoglobin which is found in red blood cells

Question 25

How is free bilirubin transported around the body?

Answer 25

Bound to albumin

Question 26

What happens to the bilirubin as it enters the liver?

Answer 26

Bilirubin dissociates from albumin

Undergoes conjugation to form bilirubin diglucuronide - this is done through the conjugation with 2 x UDP-glucuronide molecules

Question 27

What happens to the bile which enters into the small intestine via the main duodenal papilla?

Answer 27

95% of the bile is absorbed into the terminal ileum through Na + / K+ ATPase pumps and Na+ / Bile co-transporters

Question 28

What happens to the 95% of the bile which is reabsorbed?

Answer 28

Taken back to the liver via the portal vein in the entero-hepatic circulation system

Question 29

What happens to the remaining 5% of bile which remains in the small intestine?

Answer 29

converted into secondary bile acids by gut bacteria

Question 30

What happens to the bilirubin after it enters into the intestine?

Answer 30

1. Bilirubin -> Urobilinogen -> Stercobilinogen -> Stercobilin

Question 31

What happens to stercobilin?

Answer 31

Secreted out the GI systemas faeces - gives the faeces the distinctive brown colour

Question 32

What percentage of bilirubin is lost in the faeces?

Answer 32

85% is lost in the faeces as stercobilin

Question 33

How does bilirubin enter into the entero-hepatic circulation?

Answer 33

Bilirubin -> urobilinogen

urobilinogen is then taken back to the liver

Question 34

How does 1% of the bilirubin end up excreted in the kidneys?

Answer 34

bilirubin -> urobilinogen

urobiligenogen enters into the enterohepatic circulation and taken to liver

then transferred into systemic circulation and taken to kidney, along the way converted into urobilin, which is excreted in the kidney

Question 35

Describe the faeces and urine of patients with obstructive jaundice?

Answer 35

Faeces - pale - due to lack of sternobilinogen

Urine - darker due to bilirubin

Question 36

What is an ERCP?

Answer 36

Endoscopic retrograde cholangiopancreatography - is a procedure that combines upper gastrointestinal (GI) endoscopy and x-rays to treat problems of the bile and pancreatic ducts.

Question 37

What is a PTC?

Answer 37

Percutaneous transhepatic cholangiography - through common hepatic duct