Tuesday, November 30, 2010

Water at Work Within You

Blood is often equated with the very life of creatures, as in the term lifeblood. Appropriately, blood is over four fifths water. The unique qualities of water make it ideally suited as the basis of this life-giving fluid. For example, more substances dissolve in water than in any other liquid. It also has the unique ability to move freely back and forth through your body’s cell walls, carrying with it the chemicals of life. At the same time it serves as the medium in which complex chemical reactions take place within the cells.

These reactions “burn” as fuel the food you eat, generating heat, as an auto engine does when it burns fuel. But, then, how does your body keep its steady 98.6° temperature? Water! If the water in your body were another liquid—mercury, for example—heat from your cells would tend to raise your temperature over thirty times as fast as it does! This is because water requires far more heat to change its temperature than do most other substances.

But water serves in other ways, also, to control your body temperature. Rapid circulation by way of the bloodstream keeps heat relatively even all over, and quickly moves excess heat to your skin for radiating into the air. On the other hand, heat stored in your body’s water delivers welcome warmth to the extremities when you are cold.

Even with this remarkable system, your body usually does not quickly enough get rid of the heat that it generates. So another amazing property of water comes into play—evaporation. How does this help?

Well, when a pint of water evaporates, it soaks up about 1,100 times as much heat as when its temperature rises just one degree! You feel this cooling effect when a breeze dries moisture from your skin. Since about two pints of body water normally evaporate unnoticed each day through your skin and lungs by means of your breath, much excess heat is regularly released in this way.

But on a hot day, or as your activity picks up from normal levels, your sweat glands exude more water, possibly gallons in a day. Any perspiration that evaporates from the surface, rather than dripping off, carries with it immense amounts of heat—surely a marvelous cooling system!

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