What is the role of the hepatic portal system?
A. Drains the digestive organs, spleen, and pancreas and directs blood to the liver
B. Drains the lungs, heart, and vena cava and directs blood to the kidney
C. Directs blood from the kidney to digestive organs, spleen, and pancreas
D. Directs blood from the liver to digestive organs, spleen, and pancreas