5-2-2-the-mammalian-liver-structure

The mammalian liver: structure

External liver structure

• The liver is involved with the breakdown of toxic substances and the production of excretory waste; in order to carry out these roles it requires a good blood supply

  • Oxygenated blood from the heart is carried to the liver via the hepatic artery; this provides oxygen for aerobic respiration, fuelling the metabolic activity of the liver cells

  • The liver receives blood from the digestive system via the hepatic portal vein; this allows it to absorb and metabolise nutrients that are absorbed into the blood in the small intestine

  • Deoxygenated blood exits the liver in the hepatic vein and flows back to the heart

• The liver is also connected directly to the gall bladder, the role of which is to:

  • store bile, a liquid that contains:

    • bile salts for lipid digestion

    • bile pigments from the breakdown of haemoglobin

  • release bile into the duodenum via the bile duct

The liver receives oxygenated blood via the hepatic artery and nutrient-rich blood via the hepatic portal vein.

Internal liver structure

• The liver is mainly made up of cells known as hepatocytes; these cells carry out almost all the functions of the liver

• The liver cells are arranged into structures known as lobules

• Each lobule is supplied with blood by branches of the hepatic artery and the hepatic portal vein

• The blood from the hepatic artery and portal vein mixes within each lobule inside wide capillaries known as sinusoids

  • Blood within the sinusoid exchanges substances with nearby hepatocytes, allowing the hepatocytes to perform all the functions of the liver

• Each lobule is also connected to a branch of the hepatic vein that drains blood away from the lobule and into the main hepatic vein

Liver histology diagrams

Some lobule structures are visible on liver tissue micrographs