Structure And Function of liver Flashcards
How is blood supplied and drained from the liver?
Blood supply to liver: 1/3 form hepatic artery (for oxygen) and 2/3 from portal vein (I.e. From gut = nutrients/substances for metabolism)
Blood drained: via hepatic vein into the inferior vena cava
What are the functional units of the liver?
The liver acini
Hepatocytes make up which three surfaces?
Sinosoidal surface, intracellular surface and canalicular surface
What are the major functions of the liver?
Carbohydrate metabolism Fat metabolism Protein metabolism Hormone metabolism Drug/toxin metabolism and excretion Storage Metabolism and excretion of bilirubin Synthesis of proteins
What are the three types of carbohydrate metabolism?
Glycogenesis: excess glucose to glycogen
Glycogenolysis: glycogen to glucose
Gluconeogenesis: amino acid/lactate/glycerol to glucose
What are the four types of fat metabolism?
Triglyceride oxidation for energy
Lipoprotein synthesis
Excess carbohydrate and fat to fatty acids and triglycerides for storage as adipose tissue
Cholesterol and phospholipid synthesis and excretion
What occurs in protein metabolism?
Deamination and transamination of amino acids
- non-nitrogenous part to glucose or lipid
- nitrogenous part to ammonia and then urea
Which hormones are metabolised by the liver?
Insulin like growth factor -1
Angiotensinogen
Thrombopoeitin
Hepcidin
What occurs in drug/toxin metabolism?
Two phases
1) unmask functional groups by oxidation/reduction/hydrolysis
2) conjugation to charged species for renal excretion
What is stored in the liver?
Glycogen
Vit A, D &B12
Iron
Copper
What are the three sources of bilirubin?
Outline the process for its production
How is it excreted?
Haem proteins (15%), senescent red cells (80%) and ineffective erythyropoiesis (5%)
Haem to biliverdin by haem oxygenase
Biliverdin to bilirubin by biliverdin reductase
Bilirubin to bilirubin glucuronide by glucuronyl transferase for renal and biliary excretion
What are some clinical signs of liver disease?
Dupuytren's contracture Palmer erythyema Spider naevi Male gynaecomastia Ascites Jaundice
What is measured by liver function test?
Albumin: crude indicator of synthetic capacity of liver, 12g per day, maintains plasma oncoming pressure
Total protein: little utility in liver function, reflects balance between synthesis and degradation, allows calculation of globulin fraction
Bilirubin: total and direct/conjugated. Differentiate between intra- and extra-hepatic obstruction
Alkaline phosphate : removes phosphate from molecules. Secreted by cells lining biliary tract. Raised in bone disease, growth and pregnancy.
Alanine aminotransferase: catalyses transfer of amino group form alanine residues, present in all tissues, cytosolic
Aspartate aminotransferase: catalyses transfer of amino group from Aspartate residues. Cytosolic and mitochondrial
Gamma glutamyl transferase: catalyses transfer of gamma glutamyl group from peptides to appropriate acceptors. Cell membrane of various tissues. Good indicator of obstruction
Differences between unconjugated and conjugated bilirubin?
Un: not water soluble, not filtered by glomerulus, does not reach urine
Conj: water soluble, filtered at glomerulus and reaches urine
What is urobilirubin?
What can it tell you?
Urobilirubin = converted from bilirubin by gut bacteria. Absorbed by distal small intestine and excreted in urine
If present the tells you bilirubin is reaching gut. If not present and high levels of plasma bilirubin then you know it not reaching gut
