What are the three drainage systems of liver?

1. Hepatic portal vein: This is the main drainage system of the liver. It collects blood from the gastrointestinal tract, spleen, and pancreas and carries it to the liver.

2. Hepatic artery: This artery supplies oxygenated blood to the liver.

3. Hepatic veins: These veins carry blood from the liver to the inferior vena cava, which returns it to the heart.