Liver anatomy and physiology

• The liver is a peritoneal organ positioned in the right upper quadrant of the abdomen. Surface markings:

  • Right 5th rib MCL
  • Left 5th rib MCL
  • Extends down to the 10th costal cartilage on the right side
• Functions of the liver:

  • Produces bile
  • Nutrient conversion
  • Phagocytosis - removal of old or deficient RBC, WBC and bacteria
  • Synthesis
  • Detoxification - conversion of ammonia to urea
  • Storage - glycogen, fat soluble vitamins, copper and iron
• Nutrient conversion in the liver:

  • Catabolism - conversion of excess proteins into urea
  • Fat anabolism - breaks down long fatty acids into smaller molecules such as ketones
  • Hydroxylation of vitamin D to its active form
• Synthetic function of the liver:

  • Albumin - low albumin causes oedema
  • Fibrinogen
  • Clotting factors
  • Bilirubin
• Anatomical lobes of the liver are the left and right lobes that are separated by the falciform ligament
• The liver lobes can also be divided functionally. The liver is separated by an imaginary line through the gall bladder fossa. Now the caudate and quadrate lobes are now included in the physiological left side of the liver.
• The falciform ligament is a major landmark:

  • Anteriorly = ligamentum teres = remnant of the left umbilical vein
  • Posteriorly = fissure for ligamentum venosum = remnant of ductus venosus
• The liver is intraperitoneal but has a posterior bare area that is not covered by peritoneum
• Fluid can collect in the peritoneal cavity around the liver:

  • Right sub-phrenic space = space between the liver and the diaphragm
  • Sub-hepatic space
• Arterial supply to the liver is only around 20-30% of the blood supply to the liver:

  • Liver is a foregut structure and therefore supplied by the celiac trunk
  • Celiac trunk divides into the left and right hepatic artery
  • Right hepatic artery branches of to form the cystic artery which supplies the gall bladder
• The majority of the blood supply to the liver is from the portal vein:

  • Deoxygenated
  • The portal vein forms at the transpyloric plane - at the level of L1 behind the neck of the pancreas
  • The portal vein is formed by joining of the splenic vein and the superior mesenteric vein
  • Blood is then shared out between all hepatocytes
• Portal triad within the hepatocytes = branch of portal vein, branch of common hepatic artery and branches of the common bile duct
• Hepatocytes are the functional units of the liver, they are organised into hexagonal structures called lobules
• Phagocytic Kupffer cells line the sinusoids in the liver lobule. They engulf pathogens, cell debris and damaged blood cells. They are also responsible for storing iron, lipids and heavy metals
• The central vein collects blood from the sinusoids of the lobule. The central vein of all the lobules ultimately merge to form the hepatic vein which empties into the inferior vena cava.
• Paracetamol is metabolised in the liver. It is conjugated with glucuronic acid and sulfuric acid.

  Hepatotoxic metabolites (NAPQI) are produced in small amounts by cytochrome P450

  Glutathione turns NAPQI into a non toxic conjugate
• In the case of a paracetamol overdose there is not enough glutathione to detoxify the drug. Is treated with N-acytylecystine (NAC)