AWABS - Liver Physiology Flashcards
Liver anatomy
1.5-2 kg
Right and Left lobes divided by falciform ligament
Blood flow received by liver
25% of cardiac output
1.5 L blood flow per minute
Blood supply of liver
25% Hepatic artery (oxygen rich)
75% Hepatic portal vein (nutrient rich)
Splanchnic circulation
Functional divisions of liver
Factors which increase hepatic blood flow
Supine position
Ingestion of food
Hypercapnia
Acute hepatitis
P450 enzyme inducers
Factors which reduce hepatic blood flow
Upright position
PEEP / IPPV (reduced venous return)
Cirrhosis
Hypocarbia
Functional units of the liver
Hepatic lobules
Hexagonal
Arranged around central vein which connects to hepatic veins
Cords of hepatocytes radiate out
At each corner is the portal triad
Sinusoids
Metabolic units of liver
Functions of the liver
Synthesis
Metabolism
Storage
Catabolism and excretion
Immunological / Haematological
Reservoir
Substances synthesised by liver
Proteins
Fats
Bile
Substances metabolised by the liver
Glucose homeostasis and other absorbed nutrients
Substances stored by liver
Glycogen
Vitamins
Iron
Copper
Substances catabolised / excreted by liver
Drugs
Urea
Bilirubin
Reservoir function of liver
450+ mls of blood
Albumin synthesis rate by liver
200 mg/kg/day
Some examples of proteins synthesised by liver
Albumin
Clotting factors (all except factor 8 produced in liver)
Acute phase proteins inc CRP
Drug handling by liver
All substances absorbed in gut pass through liver via portal vein into the systemic circulation (1st pass)
Many also re-presented from systemic circulation (2nd pass)
Once drugs reach hepatocyte they are metabolised by SER
Phase 1 reactions
Alteration if molecular structure
Involves oxidation or reduction
Resulting compounds are more polar or water soluble
Cytochrome P450 are main players in phase 1 metabolism
What happens to metabolites after phase 1 reactions occur
After phase 1 the compound is either:
- Sufficiently water soluble and excreted
- Able to go into phase 2 metabolism
- Toxic and require further metabolism
- Bioactivated
Phase 2 reactions
Attachment of ionised groups to the drug
Methods of alterations in phase 1 and 2 reactions
