Liver anatomy

Liver anatomy

1. Largest internal organ

   • Made up of two major lobes
   • Close to gall bladder and bile duct
     • Liver produces bile and gets stored in gall bladder
     • Gall bladder = muscular bag
       • Food triggers contraction of bag
   • 1/50th of your body weight

2. Blood supply

   • Hepatic artery give O2 blood
     • only supplies 25% of blood for the liver
   • All veins from stomach spleen and intestine
     • Portal vein
       • Brings nutrients to the liver
       • Provides 75% of the blood in the liver
   • Hepatic vein --> vena cava

3. Liver - made of lobules

   • In the centre of each lobule = central vein
     • Sinusoids run from central vein
       • Sinusoids connect to portal traids
         • Portal triads - portal vein, hepatic artery and bile duct
     • Connected to hepatic vein
       • Goes back to the heart
   • Divided into 8 functional bits
     • All have individual blood supply
   • Has its own regenerative ability
     • can take away 75% and still will regrow

4. Has special macrophages

   • Kuppferr cells

5. variations in liver anatomy

   • Genetic variations
     • accessory lobes
     • Clefts that form
   • internal factors
     • portal thrombosis
       • get a necrotic area
     • Liver fibrosis
       • scarred, contracts, reduces size

6. outside of the liver

   • capsule

7. Inside the liver

   • Extracellular matrix
   • Collagen
   • Fibronectin
   • integrin

8. Fibrosis and Cirrhosis

   • Fibrosis - scar tissue builds up
     • Regenerative response
       • Blood pressure increases
         • Liver fibrosis measured on metavir scale

9. Parenchymal cells = cells of the liver

10. Cells of the liver

    • 60% = hepatocytes
      • Polarised polyhedral epithelial cells
        • Bottom of the cell
          • Blood supply at the bottom
            • Microvilli
            • Protein assembly machinery on the bottom
              • SER
              • RER
              • Secrete proteins into blood stream
                • e.g. Makes blood clotting factors
          • Glucose storage
            • Glucose --> glycogen for storage
        • Attached to eachother with tight junctions
        • Bile canaliculus on sides of cells
      • Low mitotic index
        • Unless trauma
      • Function changes with age
      • Detoxification and inactivation
      • Metabolism
      • Diagnostically important
        • Test for things that are normally contained within the liver / hepatocytes
          • Enzymes = important for metabolism
            • Test for
              • gamma- GT
              • Alkaline Phosphatase
              • Bilirubin
              • Albumin
                • Low level = something wrong
              • Aminotransferases
                • AST
                  • Aspartate
                • ALT
                  • Alanine
                • High level = something wrong
    • Biliary epithelium
      • 1-3% of liver tissue
      • Modify the content of the bile
        • Use it for excreting proteins / lipids that can't go into blood
          • Dense basement membrane
        • Transport bile --> bile duct
    • Endothelium
      • Line the hepatic portal vein brances
      • Line the aortic branches
        • Line the lymphatics
      • Line the sinusoidal endothelium
      • Barrier in the blood stream
        • Barrier against bacteria or viruses
      • Filter fluid
      • Selectively allow immune cells to enter the liver
      • Anti-thrombogenic
    • Kupffer cells
      • Hepatic macrophages
        • Phagocytose
        • Regulate microcirculation
        • Remove endotoxins
          • Important as blood is coming from the gut
        • Stimulate immune response
          • Can present antigens and produce cytokines
      • Present in liver sinusoids
      • 80% of all macrophages in the body
    • Stellate cells
      • Quiscent state = star like
      • Sit on the hepatocytes
      • Store useful lipids
      • Regulant vascular diameter
      • Upon injury --> active hepatic stellate cells
        • Proliferate and secrete ECM
          • Want to reverse this step

11. Digestive function of the liver

    • CArbohydrate and fat metabolism
      • Takes up glucose --> glycogen --> stored in hepatocyte
        • Gets converted back to glucose to meaintain blood glucose levels
      • Can use fatty acids for their own metabolism or create lipids
    • Sotrage of viramins and minerals
    • Make cholestrol
      • statins inhibit the rate limiting step of cholestrol synthesis
      • used for cell membranes

12. Production of bile

    • Recycling of bile salts to make bile
    • Released into intestine
    • Emulsify fat
      • Lipid is absorbed
    • Some things can't be excreted in urine
      • Need to be secreted into bile --> poo

13. Immune function

    • Kuppfer cells
    • Innate acting lymphocytes
    • Induction of tolerance

14. Detoxification

    • Water soluble products --> urine
    • Lipid soluble products --> bile
    • Metabolism
      • Phase 1
        • Controlled by CP450 - number varies with age , gender and organ
      • Phase 2

15. Protein production

    • Blood clotting factors
      • Hepicidin
    • Albumin
    • Transferrin

16. Normal liver

    • Damage
      • Fatty liver
        • Liver fibrosis
          • Liver cirrhosis
            • Renal failure
            • Varices in the oesophagus
            • Ascites
            • Splenomegaly
          • Liver cancer
      • Viral infection
        • Toxin
          • Autoimmunity

17. Do transient elastography to measure liver disease

    • First do blood test for liver enzymes