Liver Physiology Flashcards
How much blood does the liver receive?
1500mL/min
What supplies blood to the liver?
25-30% from the hepatic artery
70-75% from the hepatic vein
How much blood is the liver normally able to hold?
450mL
What are the functions of the liver?
Detoxification
Carbohydrate metabolism
Lipid metabolism
Protein metabolism
Storage of vitamins
Storage of iron
How does the liver carry out its detoxification role?
It filters the blood to remove the large toxins
It synthesises and secretes bile full of cholesterol and other fat-soluble toxins
It enzymatically disassembles unwanted chemicals
What occurs during the 2 phases of detoxification in the liver?
Phase I either directly neutralises a toxin, or modifies the toxic chemical to form activated intermediates
Phase II then neutralises the activated intermediated by one or more of the several enzyme systems
What carbohydrate metabolic processes occur in the liver?
Glycogen storage
Conversion of fructose and galactose to glucose
Glycogenolysis
Gluconeogenesis
How is glucose carried to the liver after being absorbed?
By the hepatic portal vein
What happens to the glucose after being transported to the liver by the hepatic portal vein?
Some glucose is released back into the bloodstream to be carried to the cells of the body
Some glucose is biochemically converted to glycogen in the liver for storage
What happens to glycogen levels during elevation of blood glucose levels?
Glycogen synthesis in the liver increases in order to restore blood glucose to normal
What happens to glycogen during decreased blood glucose levels?
Glycogenolysis in the liver is stimulated to restore blood glucose levels back to normal
How is fructose converted to glucose?
Within the liver, its it metabolised to glucose using the fructose-1-phosphate pathway of glycolysis
How is galactose converted to flucose?
It is converted to glucose through glycolysis, as it cannot bet catabolised by the body
What are the only fuel of RBCs?
Glucose
What happens during short-term fasting periods?
The liver produces and releases glucose through glycogenolysis
What happens during prolonged fasting?
During this, glycogen is depleted, and the liver synthesizes glucose through gluconeogenesis using lactate, pyruvate, glycerol and amino acids
Which lipids are synthesised in the liver?
De novo synthesis of fatty acids and cholesterol
How are fats synthesized from carbohydrates and proteins?
They are synthesized in the liver through the lipogenesis pathway, which is initiated by the entry of acetyl CoA into the pathway
What happens when carbohydrate stores are saturated?
The excess carbohydrates are converted into triglycerides
Which plasma protein is not synthesized in the liver?
Immunoglobulins
What is the first step in breaking down an amino acid?
The removal of its amine group
What is transamination?
Transamination is the transfer of an amine group from an amino acid to a keto acid, thus creating a new amino acid and keto acid
What is a keto acid?
An amino acid without an amine group
What is transamination used to synthesised?
It synthesizes non-essential amino acids
What is deamination?
Deamination is the removal of the amine group as ammonia
When is deamination required?
It is required before amino acids can be used for energy or converted to carbohydrates and fats
What is the potential problem with deamination?
If too much ammonia is produced, hyperammonaemia results and this is toxic
What are the methods of safely packaging the ammonia produced through deamination to prevent toxicity?
Urea is produced by the liver using 2 molecules of ammonia and 1 molecules of carbon dioxide
Most urea is then secreted from the liver and incorporated into the urine in the kidney to be excreted from the body
Which vitamins are stored by the liver?
A, D and B12
How is vitamin A transported?
In chylomicrons as an ester fatty acid
How does the chylomicron and retinol ester reach the liver?
Chylomicrons in circulation are acted upon by lipoprotein lipase to reduce triglycerides while the retinal ester remains unchanged
Receptors in liver mediate uptake of chylomicron remnants
These remnants are then degraded and the retinyl ester is stored
How does the liver mobilize vitamin A?
By hydrolyzing the retinyl ester
How is vitamin A carried to the tissues of the body?
It is carried by retinol-binding protein
How is iron stored in the liver?
Ferritin
How is ferritin formed?
Iron from transferrin in the blood transfers to the liver and combines with apoferritin to form ferritin
What is dietary iron used for?
It is mainly utilised for RBC production
What is the effect of chronic iron deficiency anaemia?
Decreased haemoglobin production and anaemia
