The portal system in humans is defined as a system where:

• A
  $A$ vein starts from an organ and ends in the heart.
• B
  $A$ vein enters an organ other than the heart and breaks up into capillaries.
• C
  An artery divides in an organ and starts with the coordination of capillaries.
• D
  Blood from the intestine goes to the kidney and then into the $IVC$.