Gastro 12 - Liver Basics Flashcards
What structure does the liver arise from?
The Hepatic diverticulum: grows off of the anterior part of the distal foregut. Becomes the liver, biliary system, and head of pancreas.
Where is the major site of hematopoiesis in embryos and why?
Liver is the major site. Mesodermal hematopoietic stem cells migrate from the mesonephros to the liver at about 3 weeks till about week 28 when bone marrow gets going.
What are the two sources of blood in the liver and where do they come from? Where do they all drain?
Branch of the hepatic artery, bringing blood rich in O2. Branch of portal vein that’s just been drained from the GI tract (Mesenteric vein and gastric vein). They empty into the central vein.
What are the components of a portal triad?
Branch of the Hepatic artery. Branch of the Portal vein. Bile ductile.
What are the zones of the lobules of the liver?
Zone 1, 2, and 3. Zone 1 is closet to the portal triad and most affected by viral hepatitis. Zone 3 is farthest from portal triad and closest to central vein, and sensitive to hypotension and ischemia and toxic substances.
How is the blood flow in a liver lobule? The bile flow?
The blood flows from the portal triad to the central vein (Zone 1 to zone 3) while bile flows the opposite way to reach the bile ductule.
What are the four main functions of hepatocytes?
Make proteins. Metabolize toxins and drugs. Storage. Make bile and excrete bilirubin.
What proteins do the hepatocytes make?
Coagulation factors. Complement proteins. Albumin. Apolipoproteins. C-reactive proteins. Angiotensinogen. Transferrin. Ceruloplasmin.
What enzymes does the hepatocytes make for mteabolization of toxins and drugs?
Cytochrome P450 enzymes. UDP-glucuronyl transferase. ALT and AST. Steroid hormones are turned into inactive metabolites.
What do hepatocytes store?
Glucose as glycogen. Cholesterol and triglycerides (VLDL particles). Minerals (iron). Vitamins (B12, fat-soluble).
Where does bilirubin come from?
Breakdown of heme from hemoglobin. Heme is converted to biliverdin and then to bilirubin.
Bilirubin is insoluble. How does it travel to the liver?
By albumin.
What does UDP-glucuronyl transferase do?
Transfers a glucuronyl group on to the bilirubin; this is called conjugation of bilirubin, a conjugated bilirubin.
Why are newborns susceptible to physiologic jaundice?
Have a reduced amount of UDP-GT.
What happens when there is too much unconjugated bilirubin In newborn?
Kernicterus: causes chroea, gaze abnormalities, cerebral palsy, hearing loss.
How do we treat hyperbilirubinemia?
Phototherapy.
What are the four hereditary hyperbilirubinemia disorders?
Gibert. Crigler-Najjar. Dubin-Johnson. Rotor.
What is Gilbert syndrome?
An Autosomal recessive, it is a hereditary hiperbilirubinemia. Due to a mutation in the promotor region of the UDP-GT gene, causing UDP-GT shortage. This causes slowing of bilirubin conjugation, causing slight elevation of indirect bilirubin. It is benign.
What is Crigler-Niggar syndrome Type I?
A hereditary hiperbilirubinemia. Has complete absence of UDP-GT. Unable to conjugate bilirubin. Causes jaundive and increase in indirect bilirubin, leading to kernicterus.
What are the treatments for Crigler-Nijjar type I?
Phototherapy. Plasmapheresis. Liver transplant is definitive.
What is Criggler-Najjar syndrome type II?
A hereditary hiperbilirubinemia. Produces mutated UDP-GT. The degree of hyperbilirubinemia is less than type I.
How do we differentiate b/w Type I vs Type II Crigler-Naggar syndrome?
Give phenobarbital; it induces production of hepatic enzymes, including UDP-GT. If type II, it ramps up the liver to make UDP-GT and bilirubin decreases. There will not be a change in bilirubin in type I.
What is Dubin-Johnson syndrome?
A hereditary hiperbilirubinemia. It causes trouble in putting conjugated bilirubin into the bile; it stays trapped in hepatocytes. Turns liver black. Causes increase in DIRECT bilirubin. Conjugated and direct bilirubin are the same.
What is Rotor syndrome?
A hereditary hiperbilirubinemia. Similar but milder to Dubin-Johnson.
