W14/L9 *Parslow Bilirubin Flashcards
(20 cards)
What’s the structure of bilirubin?
It’s a a tetrapyrrole - an open chain of 4 pyrrole rings
Where is bilirubin usually produced?
In the spleen
What cells are responsible for the breakdown of senescent RBCs?
Macrophages
What haem breakdown product do macrophages make?
Biliverdin
What colour is bilirubin?
Yellow
What happens to bilirubin when exposed to light?
Some of the double-bonds isomerise
What isomer of bilirubin is more soluble?
The E,E-isomer
Which isomer of bilirubin is less soluble
The Z,Z-isomer
What’s the clinical application of bilirubin isomerisation?
Phototherapy for jaundices newborns
What are the two chemical forms of bilirubin?
Conjugated and unconjugated
What’s another name for conjugated bilirubin?
Direct
What’s another name for unconjugated bilirubin?
Indirect
In which form is bilirubin excreted in bile?
Conjugated - as glucuronide
What toxicity does bilirubin have in high levels, and in which population?
Neurotoxicity in newborns
What’s the name for bilirubin-induced neurotoxicity?
Kernicterus
What gives rise to jaundice?
Hyperbilirubinaemia
What things can cause elevated bilirubin?
Neonatal hyperbilirubinaemia Bile duct obstruction Severe liver failure w/ cirrhosis Criger-Najjar syndrome Dubin-Johnson syndrome Choledocholithiasis
What is urobilinogen?
The colourless product of bilirubin reduction
How & where is urobilinogen formed?
In the intestines by bacterial action
What constitutes the normal enterohepatic urobilinogen cycle?
Some of the urobilinogen is reabsorbed from the gut and then excreted by the kidney
