5950678
Descrição
FlashCards por Lesley Howard, atualizado more than 1 year ago
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Criado por Lesley Howard
mais de 8 anos atrás
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| Questão | Responda |
| Sequence of bilirubin metabolism | Formation and transport of bilirubin in liver Uptake and conjugation of bilirubin by liver Secretion and catabolism of CB Enterohepatic resorption of UB Urinary excretion of UB |
| Majority of RBCs degraded in? | Spleen |
| Immature or defective RBC precursors degraded where? | Bone marrow |
| Cytochromes degraded where? | Tissue |
| Heme oxygenase | Removes the iron at the core of heme, converting it to green biliverdin In macrophage |
| Biliverdin reductase | Converts biliverdin to UCB In macrophage |
| Why is UCB so stable? | Removal of the iron from the heme causes the formation of intramolecular hydrogen bonds |
| UCB is transported to the liver via? | Serum albumin binds it, neutralizes its toxicity, and carries it through circulation |
| OATP | ATP independent transporter on hepatocytes Transports UCB into hepatocyte, from circulation, releases albumin back into circulation |
| GST | Entraps UCB in hepatocyte and tags it for further modification |
| UGT | Attaches a pair of glucuronic acids to UCB, creating CB |
| CB | Amphipathic thanks to two glucuronic acids attached via UGT Less toxic than UCB |
| MRP2 | Uses ATP to transport CB from the hepatocyte into the bile duct against its concentration gradient Rate limiting step |
| Urobilinogen | Colorless, formed as intestinal bacteria hydrolyze and reduce CB |
| Stercobilin | Formed as intestinal urobilinogen is auto-oxidized. Gives feces characteristic brown color |
| Excretion in stool | 90% of urobilinogen is converted to stercobilin and excreted |
| Reabsorption into enterohepatic circulation | 10% of urobilinogen is reabsorbed 9% of the reabsorbed urobilinogen is reabsorbed into the liver and re-excreted into the bile duct |
| Urinary excretion | 1% of the reabsorbed urobilinogen is auto-oxidized to urobilin (yellow) and excreted in urine |
| Diazo reaction | Dye is added to serum and the rate of purple color formation is measured |
| TBIL | Total bilirubin Diazo reaction + methanol Unfolds and solubilizes CB so the diazo can react Gives a measurement of total serum UB |
| DBIL | Directly reacting bilirubin Diazo only, no methanol Reacts with 100% of the unfolded and soluble CB, and 10-15% of the folded and insoluble UCB Gives a measurement of serum CB and a little serum UCB |
| IBIL | Indirectly reacting bilirubin TBIL-DBIL Considered to be the measurement of UCB only |
| Hyperbilirubinemia values | 2-3 mg/dL instead of 1 mg dL |
| Physiologic jaundice | Common in neonates due to immature liver Low hepatic UGT Low production of albumin Accelerated neonatal RBC destruction |
| Phototherapy | Blue light alters the conformation of UCB creating photoisomers that are more polar They cannot enter brain and are excreted from urine or bile without further modification |
| Kernicterus | Excess UCB that is not bound to albumin enters brain and forms precipitates on basal ganglia Can result in neuronal damage ranging from hearing loss to death Infants more susceptible due to immature BBB |
| Prehepatic jaundice | Caused by hemolytic anemia Destruction of damaged RBC = increased production of heme metabolites and increased serum UCB No pathology of liver or bile duct |
| Hepatic Jaundice | Caused by liver damage or infection Excretion of CB to bile duct is impaired Damaged tight junctions allows CB to leak back to circulation Damaged liver cells compromise reabsorption of urobilinogen |
| Posthepatic jaundice | Bile duct obstruction blocks from of CB into duodenum Little to no urobilinogen Damaged liver cells allow CB to leak into circulation |
| Prehepatic jaundice lab values | IBIL: Increased DBIL: Normal Urinary urobilinogen: Increased Fecal urobilinogen: Increased |
| Hepatic jaundice | IBIL: Increased DBIL: Increased Urinary urobilinogen: Increased Fecal urobilinogen: Decreased |
| Posthepatic labs | IBIL: Normal to increased DBIL: Decreased Urinary urobilinogen: Decreased Fecal urobilinogen: Decreased |
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