Liver and its Functions Flashcards
What divides the liver into 2 lobes?
→ Falciform ligament
What is the biliary tree?
system of ducts to transport bile out of the liver into small intestine
Where is the blood supply of the liver from?
→ Portal vein - Blood returning from the GI tract
- 75%
→ 25% - hepatic artery
Where do the central veins of the liver lobules drain?
→ Into the hepatic vein
→ Back into the vena cava
What do hepatocytes do?
→ 60% perform most metabolic functions
What do Kupffer cells do?
→ 30% types of tissue macrophages
What cells other than hepatocytes and kupffer cells does the liver have?
→ Stellate
→ Endothelial
What is the functional unit of the liver?
→ Hepatic lobule
→hexagonal plates of hepatocytes around central hepatic vein.
→at each of 6 corners is triad of branches of portal vein, hepatic artery and bile duct
What is around the central hepatic vein?
→ Hexagonal plates of hepatocytes
→ At each of the 6 corners is a triad of branches of the portal vein, hepatic artery and bile duct
Where does blood enter the lobules from and flow to?
→ Branches of the portal vein and hepatic artery
→Flows through small channels called sinusoids that are lined with hepatocytes
→ Hepatocytes remove toxic substances from the blood
→ Blood exits the lobule through the central vein
→ Blood flows in opposite direction to the bile
What is the oxygenation like at the hepatic artery?
→ Oxygen rich
Why does blood leaving the lobule have low levels of O2?
→ Hepatocytes near the sinusoids have used up the O2
Describe the flow of bile
→ Bile is secreted by hepatocytes → Series of channels between cells (canaliculi) →Small ducts → Large ducts → Anastomose onto common bile duct
How does the livers microstructure support its role?
→ Large SA - exchange of molecules
→ Sophisticated separation of blood from bile
→ Specific positioning of pumps to achieve localization of materials
How is portal blood filtered?
→ Through the sinusoid - removal of gut bacteria
What is bile?
→ Complex fluid : Water, electrolytes + mix of organic molecules
→ Organic molecules : bile acids, cholesterol, bilirubin + phospholipids
What are the functions of bile?
→ Essential for fat digestion + absorption via emulsification
→ Bile and pancreatic juice neutralize gastric acid as it enters the small intestine
→ Elimination of waste products from blood - bilirubin + cholesterol
→ 500mg of cholesterol converted to bile acids per day
Describe how bile gets to the gall bladder
→ Bile from hepatic ducts
→ Common bile duct
→ Duodenum or diverted via cystic duct
→ Gall bladder
→ Concentrated and stored (30-50ml)
→Released by cholecystokinin in response to presence of fat in duodenum
Causes contraction of gall bladder and relaxation of the sphincter
How is entry of bile into the duodenum controlled?
→ Opening of the sphincter of Oddi
What is bilirubin?
→ Yellow pigment formed from the breakdown of Hb
→ Useless and toxic but made in large quantities so must be eliminated
How are aged RBCs destroyed?
→ Dead/ damaged RBCs are digested by macrophages throughout the body
→ Fe is recycled
→ Globin chains are catabolized
→ Hb cannot be recycled so it is eliminated into bilirubin
How is bilirubin formed?
→ Heme is converted into free bilirubin in a series of steps
→ Released into the plasma and it is carried around bound to albumin
→ Free bilirubin is absorbed by hepatocytes and conjugated with glucuronic acid
→ Conjugated bilirubin is secreted into bile and metabolized by bacteria in the intestinal lumen
→ Eliminated in feces + urine
→Unconjugated bilirubin is conjugated to glucuronic acid
What is the major metabolite in feces?
→ Stercobilin
What is the major metabolite in urine?
→ Urobilin and urobilinogen
