Through veins oxygen to cages of an organism is transferred and carbon dioxide is removed. If to look at skin, then it is easily possible to see them. In some places examine red veins, and in some – blue-green. Here necessarily you will ask a question and why they are blue, blood – red color?
It speaks simply – two things. First, in blood there are erythrocytes containing hemoglobin. It transfers oxygen and in the course of capture of molecules is oxidized and gains bright red color. The hemoglobin containing oxygen is called oxyhemoglobin. It flows on the arteries branching in a set of capillaries where it is given to organism cages. From it hemoglobin gains crimson-blue color therefore veins seem such. If to take blood from a vein, then it, adjoining to air, instantly becomes red again.
Secondly, skin absorbs about 50 percent of waves of red range, and the rest returns back whereas absorbs waves of blue range only for 30%. Therefore veins also look blue.
Veins of extremities as hands and legs need good supply with oxygen are of special importance – they are the most active parts of a body. Distinguish superficial and deep veins. Deep are pair veins which accompany arteries of fingers, brushes, predplechyev, feet and shins. They are far from the surface of skin because of what "deep" received the name. And superficial are veins which are located near an integument, in some parts of the body they can easily be seen. Veins of extremities, especially legs, are extremely vulnerable as the biggest loading falls to the share of legs. The most widespread disease is the varicosity - it is process of twisting of vessels in a body, squeezings by them each other and violations of normal blood circulation. Also bad operation of valves of veins is the reason of varicosity that generally is a hereditary disease. Externally varicosity is shown as the sites of blood vessels, hypostases of legs, heavy feeling which are blown up strongly reddened or turned blue in legs, spasms and pain. Varicose veins strongly increase in sizes, lose elasticity and if not to treat them, then on skin ulcers can develop.