In the first few hours after a meal, the hepatic portal vein carries the nutrient-rich blood from the gastrointestinal tract to the liver. This blood is also rich in oxygen. The blood then passes into the hepatic sinusoids, where it mixes with the oxygen-rich and nutrient-poor blood from the hepatic artery. Certain toxic substances are removed from the blood during this process, as these toxic substances are taken up by the hepatocytes. This blood then drains out of the liver through the hepatic vein.