BIOCHEMICAL PROCESSES IN THE LIVER
- Role in Degradation of Hemoglobin and Formation of Bile Pigments
Hemoglobin Degradation:
- Hemoglobin Breakdown: Occurs primarily in the spleen and liver macrophages.
- Heme Oxygenase: Converts heme to biliverdin, releasing iron and carbon monoxide.
- Biliverdin Reductase: Converts biliverdin to bilirubin (unconjugated bilirubin).
BIOCHEMICAL PROCESSES IN THE LIVER
- Formation of Bile Pigments:
- Unconjugated Bilirubin: Transported to the liver bound to albumin.
- Conjugation: In the liver, unconjugated bilirubin is conjugated with glucuronic acid by the enzyme UDP-glucuronosyltransferase, forming conjugated bilirubin (bilirubin diglucuronide), which is water-soluble.
- Secretion into Bile: Conjugated bilirubin is secreted into bile and transported to the intestine.
BIOCHEMICAL PROCESSES IN THE LIVER
- Intestinal Metabolism:
- Bilirubin Conversion: In the intestine, bacteria convert bilirubin to urobilinogen.
- Excretion:
- Stercobilin: Majority of urobilinogen is oxidized to stercobilin and excreted in feces, giving stool its brown colour.
- Urobilin: A portion of urobilinogen is reabsorbed, taken up by the liver, and excreted in urine as urobilin.
DISTURBANCES IN METABOLISM OF BILE PIGMENTS
- Jaundice: Accumulation of bilirubin in the blood, resulting in yellowing of the skin and eyes.
- Pre-hepatic (Hemolytic): Excessive breakdown of red blood cells, leading to high levels of unconjugated bilirubin.
- Hepatic: Liver dysfunction (e.g., hepatitis, cirrhosis) leading to impaired bilirubin conjugation or secretion.
- Post-hepatic (Obstructive): Blockage of bile ducts (e.g., gallstones, tumours), leading to elevated conjugated bilirubin.