The blood system of the person makes really zhizneobrazuyeshchy structure of an organism which possesses a set of functions. In particular, exactly thanks to its work the cellular and fabric homeostasis is possible. It, in turn, at a fate of digestive and secretory systems provides an organism homeostasis in general.
There are two ways of hit of hazardous substances to blood: with food and other external factors and also waste products of cages. It can be both poisons, and useful substances in quantities, superfluous for an organism. The liver is designed to cope with such "harmful" substances. Not to get to hazardous substances to a blood-groove, solution of the semi-digested food from a stomach, intestines and a pancreas goes to a liver by means of a vorotny vein. Actually the liver is fed at the expense of the separate artery proceeding directly from an aorta. At the exit it is numerous branched veins and arteries unite, forming the lower hollow vein. The blood which is partially purified thus gets to the left ventricle of heart to recover on a small circle of blood circulation for enrichment with oxygen. As well as the useful substances harmful first of all get to intercellular liquid. They arrive through cell membranes there and represent products of disintegration of "food", or cell activity. Intercellular liquid comes to lymphatic system, and from there - to blood through capillaries. On the way back blood is saturated with waste products of cages where gets into kidneys. Blue blood arrives there from a big circle of blood circulation from where by means of renal veins merges with a hepatic vein, passing, eventually, into the lower hollow vein. In kidneys water-soluble waste products of cages, toxins, sometimes excessive protein and so forth which are removed in the form of urine are filtered. As kidneys are located below a liver, and the course of their blood-groove unites, turns out repeated purification of blood of possible harmful impurity. The blood purified thus gets into heart only to go to the second circle of blood circulation.