Normal Liver Function Flashcards
What is the liver made up of?
Lobules
What does a liver lobule look like and what does it contain?
Hexagon made by Hepatocytes Central vein in the middle. Portal triads on each side Each triad contains: Bile duct Hepatic artery Hepatic portal vein
Sinusoids meet in the middle
What are the functions of the liver?
Metabolism
Synthetic Function
Biliary circulation
Storage
What does the liver do?
Carbohydrate metabolism
Liver is an ‘altruistic’ organ — releases glucose into the bloodstream (compare with skeletal muscle) Glycogen storage and breakdown
Gluconeogenesis
What does the liver do?
Protein metabolism
Transamination
What is Transamination
Step by step
Amino groups are removed from amino acids and transferred to acceptor keto-acids to generate the amino acid version of the keto-acid and the keto-acid version of the original amino acid. They swap groups
Then oxidative deamination occurs.
How is ammonia removed from the liver?
In the urea cycle to make urea which is removed in the urine
What does the liver synthesise
Albumin
Clotting factors
Acute phase proteins - CRP
What is albumim?
Makes up 50% of plasma proteins
Main factor in maintaining ONCOTIC PRESSURE
Also acts as a carrier protein for calcium, bilirubin
What does Low albumin cause?
PERIPHERAL OEDEMA
What causes hypoalbuminaemia
iver disease, nephrotic syndrome, malnutrition, burns
What is the Ampulla of Vater
Where the biliary system goes into the second part of the duodenum
How are red blood cells broken down
Into-
_Haem which is broken into-
Biliverdin Bilibrubin
Iron
_Globin which is broken into-
Amino acids
What splits haem into its organic material
Haemoxygenase
What breaks down biliverdin?
Biliverdin reductase
What is the difference between biliverdin and bilirubin in terms of solubility
Biliverdin is soluble in water
bilirubin is insoluble
How is bilirubin transported to the liver?
Bound to albumin (carrier protein)but it is unconjugated
when it reaches the liver albumin leaves
bilirubin enters liver by facilitated diffusion
bilirubin conjugates with glucuronic acid by an enzyme where then it can be used.
Where are red blood cells broken down?
In reticuloendothelial system
What enzyme conjugates bilirubin with glucuronic acid
UDP glucuronyl transferase
What happens to bilirubin after it has been conjugated
Metabolised to form urobilinogen
Some is absorbed into the portal blood and then to the kidneys
In kidneys it is further metabolised into urobilin
Some is further metabolised into stercobilin
What is stercobilin used for?
Colouring faeces
What happens if too much bilirubin is produced?
Increase in unconjugated bilirubin as liver cant handle amount and so can’t conjugate all of it
What can cause too much bilirubin being produced
Haemolysis
Enzyme isn’t functioning properly
What problems can happen in the liver and what results from it?
Too much bilirubin- excess unconjugated bilirubin
Dysfunctional/No/Less Enzyme-excess unconjugated bilirubin
Obstruction in the biliary system- excess conjugated bilirubin/ No urobilinogen in faeces
What is cholestasis and what is it caused by?
Pale faeces
Obstruction of the biliary system
What are isoenzymes
Catalyse the same reactions but in different places
What can cause rise in alkaline phosphate levels?
Liver problems
Bone problems
In pregnancy problems
What does it mean if the aminotransferase levels are up?
Damage to liver cells
What does it mean if the alkaline phosphate levels are up?
Problems in the biliary system
What are bile salts synthesised from
Cholesterol
What do bile salts do?
Emulsify lipids prior to intestinal absorption
What are bile acids synthesised by?
Hepatocytes
What are the primary bile acids?
Cholic acid
Chenodeoxycholic acid
What are primary bile acids metabolised by?
intestinal bacteria
What are primary bile acids metabolised into?
secondary bile acids
What are the secondary bile acids?
deoxycholic and lithocholic acid
Where are secondary bile acids used? And what do they form?
In intestine
negatively charged bile salts
Where are bile salts recirculated?
In the Enterohepatic circulation
What are bile salts reabsorbed as?
Urobilinogen
Stercobilin
What are keto acids?
Like amino acids but instead of an amino group a ketone group sits there
What enzyme is used to perform transamination?
Transaminase
What is transaminase also known as?
aminotransferase
What does the oxidative deamination do and why is it done?
This changes the amino acid back into a keto acid. NAD+ into NADH + NH3 is applied and so NADH is used in respiration
How are aminotransferases used clinically
These enzymes should be in the hepatocytes, not the bloodstream.
If we test for aminotransferases in the blood and it is positive there is a problem
What is used as a marker when clinically testing the blood to check liver damage
Use alanine aminotransferase (ALT)
What does a rise in ALT be a sign of
hepatocellular damage
How can aminotransferases be in the blood?
Hepatic portal system is very close to the lobules of the liver and can be anastomosed
What was previously used as a marker when clinically testing the blood for liver damage
AST- aspartate aminotransferase
What was the problem with aspartate aminotransferase and why is alanine transferase good?
ALT- Sensistive AND specific
AST- Sensitive NOT specific
Found in cardiac cells also
