What is the definition of the gastrointestinal absorption?
Gastrointestinal absorption is the accidental or intentional digestion of a xenobiotic with the majority of the diffusion occurring in the ileum. If the xenobiotic is poison, then the concentration of the xenobiotic in the blood and the cells will be lower than the concentration of chemical inside of the ileum. As a result, the xenobiotic will move passively down the concentration gradient so that equilibrium may be achieved, passing into the epithelial cells of the villi and microvilli via simple or facilitated diffusion before moving into the capillaries. In addition to this transcellular, para-cellular, active transport and endocytosis may be used to transport the xenobiotic into the organism. Some toxic metal ions such as thallium, cobalt and manganese will enter the cell using the absorption channels of Iron while lead uses the same system as calcium. Therefore the body takes up the poison unsuspectingly.