Flashcards in Functions of the Liver Deck (54)
What is the main blood supply of the liver?
What is the most abundant cell type in the liver?
What is the function of hepatic stellate cells?
Unknown role but they work in the production of collagen and it leads to fibrosis if there is hyperactivation
Describe the flow of blood for the hepatocytes.
Sinusoids bring in the blood and then it exits via the central vein to the hepatic vein to the vena cava
What is the hepatic triad?
Hepatic artery, portal vein and the bile duct
What is defined by the hepatic triad?
3 cellular zones of the liver
What are the Zone 1 cells?
They receive most of the blood supply and thus are affected last in cases of ischemia. However in cases of toxins, the Zone 1 cells will be affected first.
What are the Zone 3 cells?
They are the closest to the hepatic vein and most sensitive to ischemic injury.
What will happen to the zones in liver diseases?
Zone 2 and 3 cells can function as Zone 1 cells.
What form the origin point of the biliary system?
What is the canaliculus?
Apical membranes of adjacent hepatocytes forms a channel called canaliculus.
What is the function of the canaliculus?
These canaliculi drain bile from liver and transport to the biliary ductules.
What kinds of cells line the biliary ductules?
What is special about the epithelium in the sinusoidal lumen?
Epithelium in the sinusoidal lumen is fenestrated to allow for the passage of plasma proteins as the liver is what synthesizes them
What is the role of hepatocytes in metabolism?
Hepatocytes participate in the metabolism of major nutrients – carbohydrates, lipids and proteins.
How is the liver important in glucose metabolism?
Liver plays an important role in gluconeogenesis – conversion of other sugars to glucose.
How is the liver important in glucose storage?
The liver stores excess glucose as glycogen and releases stored glucose in the bloodstream when needed.
What does impaired liver function cause in regards to carbohydrates?
Hyperglycemia after meals and hypoglycemia between meals
What is the function of the liver in regards to lipid metabolism?
The liver converts products of carbohydrate metabolism into lipids – synthesis of lipoproteins, cholesterol and phospholipids.
Hepatocytes also convert a significant portion of the cholesterol to bile acids.
What is the function of the liver in regards to protein synthesis?
The liver synthesizes all of the non-essential amino acids and all of the plasma proteins including albumin
What is the problem liver failure causes in regards to proteins?
It will lead to hypoalbuminemia – may lead to peripheral edema due to loss of plasma protein oncotic pressure and clotting disorders.
What is the function of the liver in regards to protein detoxification?
It converts ammonia into urea for excretion
What is the detoxification function of the liver?
It protects the body from toxic substances as it modifies them in “first pass metabolism” so little or none can enter systemic circulation
How does the liver achieve detoxification?
o Phase I reactions – oxidation, hydroxylation etc. – catalyzed by cytochrome P-450 enzymes.
o Phase II reactions – conjugate the substances with glucuronide, sulfate, amino acids or glutathione.
They are then secreted via urine or feces
What are the components of bile?
It is mostly made of bile acid with the rest being other constituents of which cholesterol and bilirubin are the most notable
What are the 2 primary bile acids secreted by hepatocytes?
What conjugates the bile acids in the hepatocytes?
Glycine and Taurine
What is the purpose of bile conjugation?
They are more water soluble and they can be actively absorbed in terminal ileum via apical Na+ -dependent bile salt transporter
What happens to deconjugated bile?
Deconjugated bile is usually a result of bacterial action and it will be excreted