Physiological Jaundice

Posted by e-Medical PPT
What is Jaundice?
A yellow discolouration of the skin, sclera and mucous membrane due to an increase in the serum bilirubin level. This becomes clinically evident when serum bilirubin reaches about 80-100 mol/l.
Physiological jaundice usually
  Peaks 48-72 hours
  Disappears by 1 week
  Does not present before 24 hours
Aetiology of Physiological Jaundice
 Hb in neonate =18-19g/dl and in adult =11-14g/dl
 Breakdown of  excess RBCs (Haemoglobin is a constituent of RBC)
 Hb broken into:
 Globin - a protein that is conserved and utilised
 Haem - cannot be used
     degraded and excreted  

Bilirubin is a product of this degradation.It causes yellow staining of the tissues.The bilirubin first formed is UNCONJUGATED and FAT SOLUBLE.
It cannot be excreted in bile or urine
Unconjugated Bilirubin
 - travels in plasma, bound to albumin.
 - enters the liver cells with the aid of Y &  Z  carrier proteins
 - becomes conjugated with glucoronic acid
The reaction is catalysed by an enzyme Glucuronyl Transferase

Conjugated Bilirubin is  water soluble
 It is excreted through the biliary tree into the gut.
Conjugated  bilirubin is further catabolised by intestinal flora into:
urobilinogen
stercobilin

It forms a major component of bile in faeces. (This gives the characteristic orange colour to faeces.)
A small amount is passed in the urine
Conjugated Bilirubin is unstable
Why?
Due to : 
The relatively alkaline environment of the duodenum and jejunum
Specific enzymes eg beta glucuronidase Converts back into unconjugated bilirubin.

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