Alimentary Systems 2 - Liver Flashcards
Where is the liver located?
- Behind the ribcage, but below the diaphragm
- Mainly on the right of the body
- Also in the upper left quartile
Describe the basic gross anatomy of the anterior liver surface
- Right lobe is the largest, left lobe is smaller. These are the only lobes visible in an anterior view
- Right and left separated by the falciform ligament, which becomes the ligamentum teres
- Coronary ligament above the right lobe
- Left triangular ligament above the left lobe
Describe the basic gross anatomy of the posterior liver surface
- Caudate lobe can be seen between the left and the right lobe, superior
- Quadrate lobe can be seen between the right and left lobe, inferior
- Gallbladder is seen between the quadrate love and the right lobe
- IVC and left hepatic vein at the top
Describe the couinaud classification
- 8 functionally independent segments, labelled in a clockwise direction (1-8)
- Centrally there is the portal vein, hepatic artery and bile duct
- Peripherally hepatic vein
Describe the blood supply of the liver
- Rich blood supply (25% of resting cardiac output)
- Dual blood supply (20% arterial from hepatic artery left/right)
- Hepatic portal vein (80%venous blood)
- Drains into the inferior vena cava
What is the purpose of the dual blood supply?
- Hepatic portal vein (nutrients from the stomach are delivered to be processed)
- Hepatic artery (delivers oxygenated blood)
How is the liver divided morphologically?
- Lobules
- A lobule contains a portal tract/triad containing the branch of the hepatic portal vein, hepatic artery, and a bile duct.
- 6 triads in one lobule
- Interlobular veins in the centre drain to hepatic vein
- Bile drains the opposite direction to blood (blood to centre, bile to triad)
Describe the functional division of the liver?
- Acinis
- Blood flow (diamond shape joining two interlobular veins)
- Bile flow (from centre to portal tract via canaliculus)
- Zone 3 is furthest from the portal tract
- Zone 1 is closed to the portal tract
- Zone 2 is in the middle
List the functions of the liver
- Bodys kitchen
- Biosynthesis
- Digestion
- Energy/metabolism
- Degradation
- Detoxification
List the cell types in the liver and their proportion/location.
- 80% of the cells are hepatocytes
- Endothelial cells line blood vessels and sinusoids
- Cholangiocytes line biliary structures
- Kupffer cells are phagocytes in the sinusoid
- Hepatic stellate cells store vitamin A, and are activated to be fibrogenic
Compare the structure of hepatocytes, hepatic stellate cells and kupffer cells
- Flattened, dense cell nuclei in the sinusoid may be Kupffer cells or stellate cells
- Hepatocytes are large with pale and rounded nuclei
Describe the arrangement of hepatocytes
Radiate from a central vein in sheets (cords)
Describe the function of sinusoidal endothelial cells
- Fenestrated
- Allows lipid and other large molecules to move to and from hepatocytes
List the functions of kupffer cells
- Phagocytosis
- Secretion of cytokines that promote HSC activation
How long does it take for stored liver glycogen to be used up?
It will be used in a 24 hour fast
How is glucose made in the liver?
- Pyruvate is converted to glucose by gluconeogenesis requiring 6ATP
- Glycogenolysis also occurs
How are proteins processed by the liver?
- Amino acids from the diet are converted to proteins in the liver
- Transamination can also occur, which converts non-essential amino acids to essential amino acids
- Deamination occurs to make urea which can be excreted in urine, leaving the carbon skeleton for glucose synthesis
List the conversions in transamination
- a-ketoglutarate to glutamate, proline or arginine
- Pyruvate to alanine, valine or leucine
- Oxaloacetate to aspartate, methionine, lycine
Describe the process of deaminaton in the liver
- Uses the glucose-alanine cycle
- Pyruvate + glutamate converted to alanine in the muscle cell
- Alanine travels to the liver where it is converted to glutamate again via a-ketoglutarate
- NH2 is removed from glutamate using ATP
What happens to fatty acids in the liver?
- Fatty acids from adipose cells travel to the liver and enter beta-oxidation
- Acetyl coA produced enters the TCA cycle
- Metabolism of acetoacetate can also occur
Describe the process of lipoprotein synthesis in the liver
- Glucose is converted to glycerol
- Converted to tri-acyl glycerol and apoproteins
- Lipoproteins are picked up by VLDL, which take them to triglycerides
- LDLs transport cholesterol to tissues
- HDLs pick up excess cholesterol
What is stored in the liver?
- Fat soluble vitamins including vitamin ADEK
- Stores iron as ferritin for erythropoiesis
How does detoxification occur in the liver?
- P450 enzymes
- First phase makes toxins more hydrophilic
- Second phase attaches a water soluble side chain making it less reactive
List the three functions of the liver
- Detoxification and immunological functions
- Metabolism and catabolism
- Storage, excretory and secretory functions (bile secretion)
Describe the biliary tree
- Bile canaliculi
- Small ductules, which in turn drain into small bile ducts.
- Small bile ducts coalesce into larger bile ducts for each liver segment
- These merge together to form the right and left hepatic ducts, which converge to form the common hepatic duct.
- Connected to this duct is the cystic duct, which connects the gall bladder to the biliary tree.
- The merging of the common hepatic duct and the cystic duct forms the common bile duct, which extends towards the duodenum. - The pancreatic duct joins and the vessel is then called the ampulla of Vater, which opens up into the medial wall of the duodenum at the duodenal papilla.
List the functions of bile
- Cholesterol homeostasis
- Absorption and digesition
- Toxin excretion
Where is bile produced?
- Hepatocytes produce 60% of bile
- Cholangiocytes produce 40% of bile
What does the gall bladder do?
- Stores bile
- Acidifies bile
- Concentrates bile, absorbing most of the water
