Bile Synthesis & Enterohepatic Circulation

Question 1

Where is Bile synthesised and secreted from?

Answer 1

Liver

Question 2

How does Bile get from Liver to Gallbladder?

Answer 2

Secreted by Bile Ducts from Liver into Common Hepatic Duct

Question 3

How does Bile go from Gallbladder into Small intestines?

Answer 3

Gallbladder releases bile via Common Bile Duct into Duodenum

Question 4

Where is Bile stored?

Answer 4

Gallbladder

Question 5

What is the functional & organisational unit of the Liver?

Answer 5

Lobule

Question 6

What does the Hepatic Triad consist of?

Answer 6

• Hepatic portal vein
• Hepatic artery
• Bile ductule

Question 7

Histology of Liver diagram

Answer 7

Question 8

What is the composition of Bile?

Answer 8

Question 9

Describe the process of Bile Acid Synthesis

Answer 9

Cholesterol goes into Liver -> forms Primary Bile acids by 7a-hydroxylase (Cholic acid, Chenodeoxycholic acid) -> Intestinal bacteria in large intestine turn it to Secondary Bile Acids (Deoxycholic acid, Lithocolic acid)

Question 10

Describe the Nuclear Receptor Regulation of Bile acid synthesis (3 steps and what receptors)

Answer 10

Receptors involved:
- Farnesoid X-receptor (FXR)
- Retinoic X-receptor (RXR)
Process:
- the two receptors act in conjunction
- Bile acid binds to FXR causing activation of receptors
- Inhibits transcription of hydroxylase enzyme
- Results in suppression of bile acid synthesis

Question 11

What does Enterohepatic Circulation do?

Answer 11

= Recycles bile salts
- 95% of bile salts reabsorbed into blood and recirculated into bile
- 5% bile salts broken down by bacteria in ileum and excreted

Question 12

Describe the process of Bilirubin metabolism (4 steps)

Answer 12

1. Haem broken down into unconjugated bilirubin
2. Liver uptakes bilirubin and conjugates it with glucaronic acid to form conjugated bilirubin
3. Conjugated bilirubin goes into the gut to form urobilin
4. Urobilin gets excreted via the faeces and urine