The hepatoportal system is a unique arrangement of blood vessels leading to and from the liver. The vast majority of the circulatory system is arranged in such a way that blood containing oxygen is delivered by arteries and then capillaries to various organ systems. Oxygen then leaves the blood, feeding the organs. Oxygen-depleted blood is then picked up from these same capillaries, and carried through veins back to the heart, where it is recirculated to the lungs to pick up oxygen again.

In the case of the hepatoportal system, the blood leaving capillaries throughout the intestinal system is carried by the hepatic vein NOT to the heart for re-oxygenation, but to a second set of capillaries within the liver. This blood is rich in all types of nutrients which it has picked up from the intestines. The hepatic vein sends this nutrient-rich blood through a capillary...