N2ii: Describe the functional anatomy of the liver

Gross anatomy

  • Largest visceral organ in body
  • Weight: 1.8kg
  • Can be divided up into lobules
    • Hexagonal shape and have several portal triads in periphery
    • Portal triad consists of: hepatic artery, portal vein and bile duct
    • Central vein (branch of hepatic vein) present in centre of lobule surrounded by hepatocytes
    • Sinusoids drain blood from peripheral portal triads to central vein

Functional unit


  • Diamond-shaped area
  • Approximately 100,000acini in a human liver

Acinus blood flow

  • Blood flows from portal triad towards terminal vein
  • Supply: terminal branches of hepatic artery, portal vein
  • Drainage: hepatic venules via sinusoids

Acinus can be divided into three zones

  • Zone 1:
    • AKA: periportal
    • Hepatocytes closes to portal triad
    • Blood rich in oxygen (due to proximity of hepatic artery)
    • Mitochrondria-rich cells (important in oxidative metabolism and protein synthesis)
  • Zone 2:
    • AKA: mediolobular
    • Hepatocytes between zone 1 and 2
    • Intermediate oxygen content and enzyme activity (between zone 1 + 3)
  • Zone 3:
    • AKA: centrilobular
    • Hepatocytes in periphery of acinus but closes to central vein
    • Oxygen poor blood (compared to zone 1)
    • Rich in smooth endoplasmic reticulum and CYP450 (important in drug and toxin biotransformation)
    • Area most likely to be damaged during low perfusion states / hypoxic injury
    • Area most like be damaged in states where high toxic metabolites present due to CYP450 action (ie. Site of accumulation of NAPQI in paracetamol overdose)

Other cell types within liver

  • Hepatocytes – 60%
  • Kuppfer cells – 10%
  • Others: sinusoidal, peri sinusoidal and biliary epithelial cells

Functions - Overview of functions of liver


  • Contains Kupffer cells (specialised macrophages)
  • Reticuloendothelial component filters bacteria from portal blood
  • Produces complement (part of innate immune system)


  • Micronutrients
    • Fat soluble vitamins (A, D, E, K)
    • Water soluble vitamins (folic acid, B12)
  • Macronutrients
    • Lipids (fatty aids, cholesterol, lipoproteins)
    • Amino acids
    • Glucose and other sugars
  • Blood
    • Approximately 500ml

Acid base

  • Ammonia and urea cycle


  • Phase 1 reactions: oxidation, reduction and hydrolysis
  • Phase 2 reactions: glucuronidation, sulphation, acetylation


  • Carbohydrates: glucogenesis, gluconeogenesis and glycogenolysis
  • Lipids: beta oxidation of fatty acids
  • Proteins: transminates or deaminates proteins


  • Produces bile (required for emulsification of dietary lipids)


  • Synthesis of: clotting factors, acute phase proteins, albumin, steroid binding and other hormone binding proteins
  • Converts T4 to T3
  • Activates vitamin D

Author: Suzanne Luong