Liver

• Liver

  • Largest internal organ (~5% body mass)
  • Made of several lobes, each divided to cylindrical lobules separated by connective tissue
  • Blood vessels:
  • Hepatic artery: Oxygenated arterial blood to liver
  • Hepatic vein: Deoxygenated venous blood from liver
  • Hepatic portal vein: Venous blood nutrient-rich from stomach, pancreas, spleen, intestines to liver
  • Very metabolically active
  • Key homeostatic functions
  • Sinusoids
  • Wide capillaries in lobules
  • Get arterial + venous blood
  • Give hepatocytes (liver cells) oxygen + nutrients
  • Lined by fenestrated endothelium
  • Improve gas exchange and nutrient supply
• Blood Flow

  • Interlobular vessels (triad): Blood vessels branches from hepatic artery and portal vein
  • Run between lobules in connective tissue
  • Enter lobules by portal regions in wide capillaries (sinusoids)
  • Central vein in lobule centre is hepatic vein branch, drains blood from sinusoids
• Bile

  Canaliculi:

  • Channels running through lobules between hepatocytes
  • Collect bile
  • Synthesised in hepatocytes
  • From bile salts and pigments
  • Haemoglobin breakdown products
  • Bile drains to bile ductules to bile ducts
  • Transported to gallbladder for storage
  • Bile flows opposite direction to blood
  • Blood flows in to lobule centre
  • Bile flows out to edge
• Cell

  • Hepatocytes:
  • Cuboidal epithelial
  • Microvilli (on exposed surface); increase SA for absorption and secretion
  • Wide metabolic functions diversity
  • High concentration of most organelles
  • Produce (make + secrete) bile
  • Sometimes tetraploid (4 gene sets; 92 chromosomes)
  • Fenestrated Squamous Endothelial:
  • Line sinusoids
  • Leaving gaps
  • Exposing hepatocytes to blood
  • Kupffer cells (macrophages):
  • Tissue macrophages are present in sinusoids
  • 2 functions:
  • Phagocytic (ingesting debris, bacteria; engulf in <0.01s)
  • Break down old red blood cells
  • Have bean-shaped nucleus