Liver Functions Flashcards
Other than hepatocytes, what other cell carries out major functions in the liver?
Kupffer cells - tissue macrophages
Describe the dual blood supply to the liver and the proportions of the blood supply from each vessel.
Hepatic Portal Vein - 80%
Hepatic Artery Proper - 20%
Describe how the liver can produce glucose from lactate.
Lactate dehydrogenase is used to convert lactate to pyruvate and then the pyruvate is converted to glucose.
This is an energy-consuming process: 6 ATP used
Describe how amino acids can be converted to glucose in the liver.
Amino acids can be DEAMINATED to produce pyruvate and then glucose.
E.g. alanine —> pyruvate —> glucose
Describe how triglycerides can be converted to glucose in the liver.
Triglyceride —> glycerol —> glucose
What proportion of plasma proteins are produced by the liver? What makes up the remainder?
90% - the remainder are gamma immunoglobulins
How can the liver metabolise fat as an energy source?
The liver can convert the fatty acids to acetyl CoA, which then enters the TCA cycle
It can convert 2 x Acetyl CoA into acetoacetic acid for transport in the blood
Synthesise lipoproteins, cholesterol and phospholipids
What can the liver convert acetyl CoA into for travel to a different tissue?
Acetoacetic acid
What other lipid molecules does the liver synthesise?
Lipoproteins, phospholipids, cholesterol
What is CETP?
Cholesterol ester transfer protein - shuttles cholesterol from HDLs to LDLs
What is cholesterol synthesised from?
Acetyl CoA
How much bile can the gallbladder store?
15-60 mL
What are the two pathways that the liver uses for secretion and absorption?
Secreted into the canaliculi for drainage into the bile duct
Secretion into the blood sinusoids
What are the major components of bile?
Cholesterol, Bilirubin, Bile Salts, Bile Pigments, Phospholipids, Bicarbonate, Water
How are primary bile acids made?
Primary bile acids are made by the oxidation of cholesterol via the addition of carboxyl and hydroxyl groups to produce cholic acid and chenodeoxycholic acid (addition of carboxyl and hydroxyl groups makes it more water soluble)
What are primary bile acids conjugated with and what do they form?
Primary bile acids are conjugated with taurine and glycine to form taurocholic acid and glychocolic acid (this makes it more water soluble)
What do bacteria in the ileum do to primary bile salts?
They deconjugate the bile salts making them less water soluble and more lipid soluble so they are more easily reabsorbed
What are the roles of bile?
Digestion/absorption of fats
Excretion of a variety of substances via the GI tract
Neutralise acid chyme from the stomach
What stimulates the release of bile during the intestinal phase of gastric secretion?
Cholecystokinin causes contraction of the gallbladder and relaxation of the sphincter of Oddi
What circulation is used to return bile salts to the liver?
Enterohepatic Circulation - less that 5% of bile salts are lost
What percentage of bile salts are reabsorbed?
95%
Describe the detox and excretory functions of bile.
Liver breaks down/inactivates steroid and peptide hormones and then secretes them into bile for excretion.
Similarly, involved in drug metabolism and excretion
Excretory route for excess cholesterol - lecithin allows more cholesterol in the micelles. Too much cholesterol will result in it coming out of solution and forming gallstones.
Where does the bilirubin that bile excretes come from?
Break down of haem from old red blood cells. Iron from the haem is removed in the spleen and conserved.
Porphoryn group is reduced to billirubin and conjugated with glucuronic acid in the liver.
What vitamins are stored by the liver?
ADEK
How does the liver store iron?
As Ferritin
How is the liver involved in calcium metabolism?
UV light converts cholesterol to a vitamin D precursor. The precursor requires double hydroxylation to convert it to an active form - first in the liver and then in the kidneys. So liver disease can lead to rickets.
