8. Liver metabolism
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- What supplies the liver with blood?
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Dual supply:
-portal vein rich in nutrients
-hepatic artery - for O2 -
What are the 2 important cell types in the liver?
What is the function of each? -
-Kupffer's cells - phagocytic
-Parenchymal cells - hepatocytes - List the 5 categories of hepatic functions:
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1. Metabolic
2. Synthetic
3. Catabolic
4. Metabolic
5. Storage - What are the metabolic processes that occur in the liver?
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-Glycogen homeostasis
-Lipid metabolism
-Amino acid transamidation - What gets synthesized in the liver?
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-Almost all plasma proteins
-Bile acids (from cholesterol) - What does the liver STORE?
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Lipid soluble vitamins
Iron
Copper
Glycogen
Triglycerides - What does the liver catabolize?
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Hormones
Proteins
Drugs/Toxins - How is stuff excreted from the liver?
- In bile
- Why is the gallbladder important?
- It stores bile juice, which functions in digestion.
- How does bile juice affect digestion?
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1. Emulsifies fats/fatty acids
2. Allows fat-soluble vitamins to be absorbed
3. Neutralizes stomach acid
4. Allows drugs/toxin excretion
5. Allows body to rid of sterol ring - What are the hematologic functions of the liver?
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1. Synthesis of clotting factors
2. Hematopoiesis in embryos occurs here.
3. Part of RES, gets rid of senescent RBCs. - How does the liver detoxify the body?
- By catabolizing and excreting toxins through oxidation, reduction, hydrolysis, and conjugation.
- What part of hematology does the liver always come up in, coming back to haunt me?
- BILIRUBIN metabolism
- What are the 4 steps in bilirubin metabolism?
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1. Formation
2. Transport to liver
3. Conjugation
4. Excretion - What is urobilinogen?
- The reduced product of diglucuronide (direct bilirubin) formed by intestinal bacteria; most is excreted by the liver.
- What types of problems cause prehepatic jaundice?
- Those that cause increased bilirubin production exceeding the liver's ability to conjugate it.
- What are some specific causes of prehepatic jaundice?
- 1. Hereditary hemolytic anemias, HDN, transfusion reactions, Physiologic jaundice of Newborn, congestive heart failure...
- Why does physiologic jaundice of the newborn develop?
- B/c UDP-glucuronyltransferase is one of the last liver functions to mature.
- What types of problems cause hepatitic jaundice?
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Retention/Regurgitation jaundice
-Decreased bilirubin uptake by the liver cells. - What are some specific causes of hepatitic jaundice?
- Gilbert's, Crijler/Najar, Dubin Johnson, and other liver diseases.
- How is it that the direct bilirubin can be increased in hepatitic jaundice?
- Glucuronyl transferase (the conjugating enzyme) leaks into the sinusoids from endothelial cells.
- What type of problems cause post-hepatitic jaundice?
- Obstruction of the biliary network, either intra or extrahepatic.
- What are specific causes of post hepatic jaundice?
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-Common bile duct stones
-Cancer of bile ducts/pancreas
-Bile duct stricture - What is the main problem in Gilbert's syndrome?
- The hepatocytes are unable to take up bilirubin from the blood.
- What is the main problem in Crigler-Najar and Physiologic Jaundice of Newborn?
- Conjugation by the liver is impaired - i.e., glucuronyltransferase deficiency.
- What is the main problem in Dubin-Johnson syndrome?
- Hepatocytes can't secrete conjugated bilirubin - but they CAN conjugate it at least.
- What builds up in Gilbert's syndrome then?
- Unconjugated bilirubin in the blood; thus total bilirubin
- What builds up in Crigler-najjar and Physiologic jaundice then?
- Unconjugated bilirubin gets retained by the liver.
- What builds up in Dubin Johnson then?
- Conjugated bilirubin - gets spit back into the blood because it can't get secreted into bile.
- Which form of bilirubin is water soluble?
- Direct/conjugated
- What is the classic method for bilirubin measurement?
- Diazo reaction
- Which bilirubin form reacts with diazo reagent?
- Only water-soluble, conjugated.
- How is total bilirubin measured then?
- By adding a caffeine accelerator, allows both fractions to become H2O-soluble.
- What 3 additional methods can be used for measuring bilirubin?
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1. HPLC
2. Direct-reading bilirubinometer
3. Reflectance spectrophotometry (Ektachem) - What is a direct-reading bilirubinometer used for?
- only neonates
- What is the urine bilirubin a test for?
- Conjugated hyperbilirubinemia - it's a qualitative screen only.
- What specimens are tested for urobilinogen?
- Urine and feces.
- What is an important function of the pancreas?
- Excretion of digestive enzymes.
- the pancreas is described as a gland with what 2 types of functions?
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-exocrine
-endocrine - What important enzymes are produced by the pancreas?
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-Amylase
-Lipase
-Pepsin
-Trypsin/chymotrypsin/elastase - So what do the pancreatic enzymes break down?
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-Starch
-Lipids
-Proteins
-Amino acids - What metabolic diseases can damage the liver?
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1. Hemachromatosis
2. Wilson's disease (copper)
3. Reye's syndrome (chickenpox)
4. Alcoholism (cirrhosis)