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06-06-2008, 02:28 PM
mDefinition:
Yellow discoloration of skin, mucus membrane and sclera due to increase of bilirubin in blood > 2mg/100ml.
mMetabolism of bilirubin (bile pigment):
The old RBCs are destructed in the R.E.S. giving Haem and Globin. The Haem is divided into iron and biliverdin.
Biliverdin is suspended on Albumin and form Haembilirubin {Bilirubin A}{Unconjugated Bilirubin}{Indirect Bilirubin} which is of high molecular weight and not water soluble. So, it pass to the liver & not secreted throug kidney.
In the liver it will be conjugated with Glucoronic acid in the presence of Glucoronyl Transferase Enzyme to form Cholebilirubin {Bilirubin B} {Conjugated Bilirubin}{Direct Bilirubin}. It is of low M.W. and water soluble so it can be secreted in urine. Only small fixed amount is secreted in urine. Most of the cholebilirubin is secreted into the common hepatic duct then into the intestine in which:
1) Bile salts do its important functions and re-absorbed into portal circulation where it reach the liver and re-excreted.{Entero-Hepatic circulation}
2) Bilirubin finally gives Bilinogen. Part of Bilinogen is oxidised in the intestine to give Stercobilin "responsible for the normal colour of faeces". Other part is absorbed to the liver then to systemic circulation to be excreted with urine "colourless unless oxidised".
m Types of Jaundice:
(I) Haemolytic jaundice. (II) Hepatocellular jaundice.
(III) Obstructive jaundice.
SOURCE: DR. AYMAN SALEM'S BOOK
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