Biliary and pancreatic pathology

Question 1

Which cells release bile?

Answer 1

Hepatocytes

Question 2

How is bile release stimulated? Which hormone?

Answer 2

Eating stimulates cholecystokinin (CCK) release which results in bile release into the bowel

Question 3

Which cells produce cholecystokinin?

Answer 3

I cells in the duodenum

Question 4

What is the role of bile?

Answer 4

1. Helps the body absorb the necessary fats - Emulsification of dietary fat (vital for absorption)
2. Helps eliminate waste products - Excess cholesterol, bilirubin, non water-soluble xenobiotics (conjugated by hepatocytes)
3. Signalling molecules - Activate MAPK pathway, ligands for receptor TGR5, activate hormone receptors e.g. FXRα

Question 5

The gall bladder stores and concentrates bile produced by the liver, what is bile concentrated with?

Answer 5

Bile is concentrated with water and ion absorption by the gallbladder mucosa (simple columnar epithelium with rugae)

Question 6

What does bile contain?

Answer 6

1. Bile acids
2. Cholesterol
3. Phosphatidylcholine
4. Bilirubin

Question 7

What are the different bile acids contained in bile?

Answer 7

1. Cholicacid
2. Chenodeoxycholic acid
3. Glycine conjugates
4. Taurine conjugates
5. Secondary bile acids (deoxycholic acid, lithocholic acid)

Question 8

Explain the process of bilirubin processing from formation to excretion

Answer 8

1. Old RBCs are phagocytosed in the liver, this liberates globin and bilirubin (derived from haeme)
2. Iron and globin are recycled
3. Bilirubin is secreted into the bile which passes into the small intestine and then the large intestine
4. In the large intestine, bacteria convert bilirubin into urobilinogen
5. Some urobilinogen is absorbed back into the blood, converted to urobilin, and excreted in urine (responsible for yellow urine colour)
6. Most urobilinogen is excreted in the faeces in the form of stercobilin (given faeces its brown colour)