Answer:
1. Many drugs that are absorbed through the GIT are substantially metabolized by the liver before reaching general circulation.
2. The surplus glucose is absorbed by the blood from the digestive tract. This glucose is then absorbed by the hepatic cells and converted and stored as glycogen.
3. Kuppfer cells which lines the liver sinusoids engulf and destroy bacteria and other microbes that have entered the blood through the rectum. Poisonous and badly smelling nitrogenous gases are converted into urea by these cells as well.
4. Surplus amino acids are absorbed by the blood from the intestine. These surplus amino acids are absorbed by the liver cells from the blood and then undergo deamination. The amino group(-NH2) so separated is converted into glucose.