Liver

• Liver is the largest internal organ (~5% of body mass) and situated in the abdomen, it is made of several lobes, each of which divided into cylindrical lobules separated by connective tissue
• Liver has three blood vessels attached:

  • Hepatic artery: Brings oxygenated arterial blood to liver
  • Hepatic portal vein: Brings venous blood rich in nutrients directly from the stomach, pancreas, spleen, small and large intestines to liver
  • Hepatic vein: Removes deoxygenated venous blood from the liver to vena cava
• Interlobule vessels (triad): Blood vessels branching from hepatic artery and portal vein; run between lobules in connective tissue, enter lobules in portal regions in wide capillaries (sinusoids)
• Sinusoids receive a mixture of arterial and venous blood to supply hepatocytes (liver cells) with oxygen and nutrients; they are lined by a layer of fenestrated endothelial; improving gas exchange and nutrient supply, central vein in lobule centre is branch from the hepatic vein, which drains blood from the sinusoids
• Hepatocytes (”liver cells”): Cuboidal epithelial cells, have microvilli (on exposed surface) to increase surface areas for absorption and secretion, have a wide diversity of metabolic functions so high concentration of most organelles; produce (make and secrete) bile and are occasionally tetraploid (4 sets of the genes; 92 chromosomes)
• Kupffer cells (macrophages): Tissue macrophages are present in sinusoids and have two functions: phagocytic (ingesting debris, bacteria - engulf in <0.01s) and breaking down old red blood cells, also have bean-shaped nucleus
• Liver is metabolically very active and has important homeostatic functions