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What are functions of bile salts?
- Conjugated bile acids
- Necessary for micelle formation
- Facilitates emulsification and absorption of fat and fat-soluble vitamins
- Decreased bile salts = Decreased fat absorption
In what conditions/disorders would you expect deficiency of bile salt secretion?
- Liver disease
- Bypass of distal ileum
- Bacterial overgrowth - decreased motility --> stasis of bacterial --> deconjugates bile salts --> ineffective micelle formation and fat absorption
How is unconjugated bilirubin excreted from the body?
- Heme portion of RBC oxidized into biliverdin, which is then reduced to bilirubin
- Bilirubin then binds to protein and enters vascular system [Bilirubin-Albumin Complex]
- This type of bilirubin CANNOT be excreted
- Has potential to build up in lipid parts of membranes, such as the brain
- Lipid soluble
- Measured as indirect bilirubin
How is conjugated bilirubin excreted from the body?
- UN-conjugated bilirubin transported to liver and passed from one protein to another.
- Once in smooth endoplasmic reticulum of liver, exposed to glucuronyl transferase
- Conjugates bilirubin into bilirubin glucuronides = DIRECT bilirubin
- Now water-soluble
- Can be excreted by kidneys
- Can go through biliary system and small intestine and be excreted in feces as well
Between conjugated and unconjugated bilirubin, which is most toxic to body and why?
- Unconjugated = most toxic
- Builds up in lipid membranes (i.e., brain)
- Can cause necrosis of neurons and glia (connective tissue)
- KERNICTERUS or Bilirubin Encephalopathy
What would urine positive for bilirubin and negative for urobilinogen suggest? (p.38)
Intrahepatic or extrahepatic biliary obstruction
Would bilirubin in urine reflect conjugated or unconjugated form?
Conjugated – water soluble; can be excreted by kidneys in urine