Flashcards in Bile Pigments Deck (19):
How long do erythrocytes circulate in the body?
Where are erythrocytes broken down?
Broken down by macrophages in the red pulp of the spleen and the Kupffer cells of the liver.
What are the two breakdown products of haem?
Unconjugated bilirubin and iron.
What colour is unconjugated bilirubin?
Is unconjugated bilirubin hydrophilic of hydrophobic?
Hydrophobic, so is transported to the liver bound to albumin.
How is bilirubin made hydrophilic in the liver?
Conjugated to glucuronic acid.
What happens to conjugated bilirubin once it has been formed in the liver?
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.
What is the difference in the molecular shape of haem and bilirubin?
Haem is a ring (porphyrin ring) but bilirubin is linear.
What is the difference between direct readings and indirect readings of bilirubin?
Direct reading measure the levels of bilirubin diglucuronide (conjugated bilirubin), indirect readings measure the levels of unconjugated bilirubin.
What are the consequences of hyperbilirubinaemia?
Hyperbilirubinaemia = too much bilirubin in the blood.
This causes bilirubin to start diffusing into the tissues and turning them yellow (jaundice).
What type of jaundice results in a big increase in indirect bilirubin?
Pre-hepatic e.g haemolytic anaemia
What type of jaundice results in a big increase in direct bilirubin?
Post-hepatic/obstructive jaundice e.g cholestasis
Which type of jaundice increases both direct and indirect readings?
Hepatic e.g cirrhosis, because the liver can't process the compounds.
What are the 4 causes of cholelithiasis?
Too much cholesterol
Too much bilirubin
Too little bile salts
Incomplete or infrequent emptying of the gall bladder
What are the two types of gall stones?
Cholesterol stones - yellow-green
Bilirubin stones - darker colour
(Also calcium stones can form)
What are the risk factors for gall stones?
Obese (there will be more cholesterol in the bile)
Family history of gallstones
Rapid weight loss
High fat, low fibre diet
Does conjugated bilirubin appear in urine?
No, only in cases of liver disease or bile duct obstruction.
Is urobilinogen normally found in urine?
Only in small amount, an elevated level indicates haemolytic anaemia or liver disease.