Application:
• Dual blood supply to the liver and differences between sinusoids and capillaries
Hepatic Lobules
The liver is composed of smaller histological structures called lobules, which are roughly hexagonal in shape
- Each lobule is surrounded by branches of the hepatic artery (provide oxygen) and the portal vein (provide nutrients)
- These vessels drain into capillary-like structures called sinusoids, which exchange materials directly with the hepatocytes
- The sinusoids drain into a central vein, which feeds deoxygenated blood into the hepatic vein
- Hepatocytes also produce bile, which is transported by vessels called canaliculi to bile ducts, which surround the lobule
Structural Organisation of the Liver
Sinusoids
Sinusoids are a type of small blood vessel found in the liver that perform a similar function to capillaries (material exchange)
- Sinusoids have increased permeability, allowing larger molecules (e.g. plasma proteins) to enter and leave the bloodstream
The increased permeability of sinusoids is important for liver function and is due to a number of structural features:
- The surrounding diaphragm (basement membrane) is incomplete or discontinuous in sinusoids (but not in capillaries)
- The endothelial layer contains large intercellular gaps and fewer tight junctions (allowing for the passage of larger molecules)
Structural Differences Between Sinusoids and Capillaries
