It is no exaggeration to say that the planet Earth in this way, as it is created water.Liquid water covers ¾ planet's surface, solid water (ice and snow) covers 1/5 of the Earth's land, water vapor saturated atmosphere.Due to the high heat capacity of water, the Earth does not have time to cool down or during the night, or "overheated" during the day, temperature variations are relatively small.It is this climate allowed arise and preserve life on Earth, and thus the man.

water in living cells

life originated in water.In the ancient seas were the first living creatures - single-celled.In the aqueous medium in which they were, these cells they need substance imbibed in an aqueous solution.Whatever audio steps I did evolution since the principle remains the same: all the chemical reactions occurrin
g in the cells between the substances dissolved in water.This is true for plant cells and animals, and for single-cell, for those cells that make multicellular organisms - including man.

Thus, the water in the human body provides the metabolism, which constitutes the basis of life.But this is not the only function of the water at the cellular level.In the vicinity of the cell membrane it acquires tackiness comparable with ice.So the water "cements" the cell and it creates a protective barrier.

special role played by water in the nerve cells.Passage between the two signals associated with the transfer of sodium and potassium ions across their membranes, and this transfer, too, provides water.

Extracellular water

water in the body is found not only in the cells.It is part of the interstitial fluid, plasma (the liquid part of blood) and lymph.Intercellular fluid surrounding the cells that absorb the nutrients from it and recovered metabolites therein.We can say that human cells "live" in the interstitial fluid, as the ancient single-celled living in a primitive sea.

in plasma water becomes a kind of "vehicle" for blood cells, proteins and other substances that make up the plasma.

Not only blood and lymph, and all body fluids are aqueous solutions.For example, saliva is water at 99%.Water promotes the excretion of harmful metabolic products it, because the urine - is also an aqueous solution.
Another important function of water - thermoregulation.Evaporate water from the breathing and the skin surface in the form of sweat, the human body sends excess heat, which prevents it from overheating.

With so many functions of water in the human body must be quite large.And so it is.The average body water content is 75%.This figure varies depending on age, weight, physique, sex.In men, the percentage of water is higher than in women;in children than in the elderly.And the water content varies in different tissues.Least its bone (10-12%), but most of all - in the blood (up to 92%).Quite a high water content in the brain - to 85%.