SS1. The excetory role of bile Flashcards
What is responsible for the colour of bile?
Bile pigments, excretory products of haem (haemoglobin).
What is the major bile pigment?
unconjugated bilirubin.
When is unconjugated bilirubin formed?
when RBCs are broken down in spleen.
How is bilirubin transported to the liver?
Plasma albumin.
Where does 80% of unconjugated bilirubin conjugate to in the liver?
glucoronic acid. Forms bilirubin diglucuronide.
Where does 20% of unconjugated bilirubin conjugate to in the liver?
Sulphate or other hydrophilic agents.
What happens to bilirubin diglucuronide in the large intestine?
Hydrolysed by bacteria.
What 3 products does hydrolysed bilirubin diglucuronide form?
1) urobilinogen (highly H2O soluble, colourless)
2) stercobilin
3) uribilin (gives faeces the brown colour).
What happens to urobilinogen?
some is reabsorbed from intestine to bloodstream, where its secreted into bile by liver or excreted by kidneys.
What is jaundice?
high concentration of bilirubin in the blood (hyperbilirubinaemia). Characterised by yellow skin, eyes & deep tissue.
What causes jaundice? (3)
excessive haemolysis of red cells
Impaired uptake of bilirubin by hepatocytes
Obstruction of bile flow either through canaliculi or bile ducts
What is hepatic jaundice?
jaundice resulting from the failure of the liver to take up conjugate bilirubin. Caused by hepatitis & cirrhosis
What is obstructive jaundice?
Bile prevented from flowing into intestine, caused by gall stones, strictures or tumours of bile ducts or pancreatic tumours. Pale faeces.
How is cholesterol obtained?
Mostly synthesised in liver + intestine, but can be taken in by diet.
What is the function of plasma?
Essential component of plasmamembrane, required for synthesis of bile, steroid hormones & vitamin D.
