Bile Pigments

Question 1

How long do erythrocytes circulate in the body?

Answer 1

120 days

Question 2

Where are erythrocytes broken down?

Answer 2

Broken down by macrophages in the red pulp of the spleen and the Kupffer cells of the liver.

Question 3

What are the two breakdown products of haem?

Answer 3

Unconjugated bilirubin and iron.

Question 4

What colour is unconjugated bilirubin?

Answer 4

Yellow-orange.

Question 5

Is unconjugated bilirubin hydrophilic of hydrophobic?

Answer 5

Hydrophobic, so is transported to the liver bound to albumin.

Question 6

How is bilirubin made hydrophilic in the liver?

Answer 6

Conjugated to glucuronic acid.

Question 7

What happens to conjugated bilirubin once it has been formed in the liver?

Answer 7

It is excreted in the bile. Bacteria in the large intestine convert conjugated bilirubin to urobilinogen (lipid soluble).
10-15% of the urobilinogen is reabsorbed and carried back to the liver via the portal vein bound to albumin.
90% of the urobilinogen is oxidised by the bacteria to stercobilin which is excreted with faeces (giving faeces its brown colour).
Half the reabsorbed urobilinogen is taken up by the liver and resecreted into the bile and excreted. The other half of the reabsorbed urobilinogen is carried in the blood to the kidneys, converted to yellow urobilin and excreted in the urine.

Question 8

What is the difference in the molecular shape of haem and bilirubin?

Answer 8

Haem is a ring (porphyrin ring) but bilirubin is linear.

Question 9

What is the difference between direct readings and indirect readings of bilirubin?

Answer 9

Direct reading measure the levels of bilirubin diglucuronide (conjugated bilirubin), indirect readings measure the levels of unconjugated bilirubin.

Question 10

What are the consequences of hyperbilirubinaemia?

Answer 10

Hyperbilirubinaemia = too much bilirubin in the blood.

This causes bilirubin to start diffusing into the tissues and turning them yellow (jaundice).

Question 11

What type of jaundice results in a big increase in indirect bilirubin?

Answer 11

Pre-hepatic e.g haemolytic anaemia

Question 12

What type of jaundice results in a big increase in direct bilirubin?

Answer 12

Post-hepatic/obstructive jaundice e.g cholestasis

Question 13

Which type of jaundice increases both direct and indirect readings?

Answer 13

Hepatic e.g cirrhosis, because the liver can’t process the compounds.

Question 14

What are the 4 causes of cholelithiasis?

Answer 14

Too much cholesterol
Too much bilirubin
Too little bile salts
Incomplete or infrequent emptying of the gall bladder

Question 15

What are the two types of gall stones?

Answer 15

Cholesterol stones - yellow-green
Bilirubin stones - darker colour
(Also calcium stones can form)

Question 16

What are the risk factors for gall stones?

Answer 16

Female 
Over 40
Obese (there will be more cholesterol in the bile)
Family history of gallstones
Rapid weight loss
High fat, low fibre diet

Question 17

Does conjugated bilirubin appear in urine?

Answer 17

No, only in cases of liver disease or bile duct obstruction.

Question 18

Is urobilinogen normally found in urine?

Answer 18

Only in small amount, an elevated level indicates haemolytic anaemia or liver disease.

Question 19

Which bile pigment is a breakdown product of haem?

Answer 19

Bilirubin