In human anatomy, the<unk> s are the blood vessels that drain de-oxygenated blood from the liver and blood cleaned by the liver (from the stomach, pancreas, small intestine and colon) into the inferior vena cava.
They arise from the substance of the liver, more specifically the central vein of the liver lobule.
None of the<unk> s have valves.
Hepatic vein
Splenic vein
Hepatic portal system
Splenic artery
Azygos vein
Common bile duct
Thoracic aorta
Iliac vein