Two chemical barrier

Life, the metabolism is constant interaction of the organism with the greatest number of chemical agents. Among them there are not only relevant, useful substances that are our friends and enemies that can cause harm. In the body formed two lines of chemical self - General, to protect against any foreign substances, and special, for protection against foreign proteins, in particular from the living enemies, especially microbes.
The first barrier can be called antitoxic, for it protects the body from chemical "outsiders" - that may be of poisons, toxins. The flagship, the leading organ of this protection is, as we already know, the liver. Alien substance of the surrounding world are in our bodies, first of all, through the organs of digestion, whence come directly into the blood. So hepatic barrier blocks the way it is the blood that flows away from the gut. Undesirable substances that enter the bloodstream through the lungs, and formed in the organism, still during continuous mixing moving blood pass through the liver and neutralizes; there are other filters. The outstanding role played by allocating organs that help as soon as possible to remove unwanted toxins from the body.
It was amazing to methods of recognition and their alien molecules available to the liver and other barriers and allowing to keep "outsiders" and to ignore all useful. Of course, the barrier services are not boundless. Is it good or bad? Oddly enough, the answer was not available. On the one hand, it is bad that the barriers are not omnipotent, because when large doses of toxins from harm not be saved. On the other hand, however, modern man is to a certain extent even good. For example, we take medicine, which is for the body to foreign substances, liver, fortunately, delays are not completely. Taken by pill or powder will work weaker than in the case of the introduction of the drug directly into the bloodstream, bypassing the liver barrier. However, they will still work.
The second barrier, specifically aimed at foreign proteins, called immune system (from lat. immunitas - liberation, freedom from something, or to be more precise in meaning from France. immune - protected). The doctrine of immunity - immunology - happy world with new and new important discoveries and today it is perhaps the most cutting edge of medical science.