Water, which is vital for all forms of life, does not exist in any of the 63 celestial bodies in the Solar System. Oceans and seas cover 70 percent of the Earth’s surface. Meanwhile there are lakes and rivers on lands. The snow covering the summits of high mountains is the frozen form of water. A significant amount of water in the world is in the skies. In each one of the clouds there are thousands, sometimes millions of tons of water. Some of this water fall on Earth. There are also water vapor in the air we breathe. Rain, seas, rivers, oceans and the tap water…A great majority of people are so much accustomed to the existence of water that they rarely think about the significance of the great amounts of water on Earth while there exists no water at all in any celestial body we know. The fact that the water on Earth is potable is another miraculous situation.
Although a person can live 1-2 weeks without food, he cannot live more than 3-4 days without drinking water. Human body is made up of about 55-70 percent water. Through activities like respiration and sweating we can lose 2-3 liters of water a day.
Water detector in our body: Hypothalamus
In our body there are systems that detect the slightest changes in the amount of water. The foremost of these systems is hypothalamus which is a part of our brain that is about the size of a pea. When the amount of water decreases in blood hypothalamus immediately detects it and the pituitary gland which is located just under the hypothalamus secretes a hormone called ADH.
The bloodstream carries this hormone to kidneys. Just like the matching of a key to a lock, there are special receptors in kidneys that are convenient for this hormone. By the moment hormones reach these receptors kidneys start to save water and water excretion is decreased to minimum.
If there were no kidney cells that recognize the pituitary hormone and implement the order for “water reduction” brought by this hormone, we had to drink 15-20 liters of water a day in order not to die of thirst.
As is the case with all living beings, water is the most important source of life for man. Water takes place in almost all bodily functions such as adjustment of body temperature, transportation of nutrients and oxygen, removal of waste materials from cells and facilitation of digestion. It also protects organs and tissues. For instance if we lost only 2 percent of the water enclosing our cells, we would have an energy loss of 20 percent and feel very exhausted. Only this property of water makes us understand the significance of water for human life.