They used, for example, geometric methods for water supplies relatively stable free volume as oceans, lakes and glaciers. They also used methods based on statistical averages water concentrations, they are more hypothetical in space, for bookings of the lithosphere, whose boundaries are more or less vague, also may be hypothetical in space and time for bookings of the atmosphere and soil, the volume is very variable. (4) The less bulky reserves are those closest quantification (air, surface water courses, soil moisture). These attempts have primarily served to compare the average volume of water in each subset of stocks with circulating, in order to deduce the overall average times of renewal, for which statistical indicators are only significant differences. Thus, MI Uvovich (3) estimated the time of renewal means that for the oceans is three thousand years, glaciers (ice caps and continental glaciers) of eight thousand years, for lakes seventeen aquifers for 4000-5000 years for the soil (moisture) from one year to the rivers of approximately twelve days and atmospheric moisture a week. Water can deplete fossil fact, water resources, from the time the interest was defined and evaluated, initially were associated with flows maintained by the eternal return of the water cycle, the possibility of capturing and use: water is widespread as a renewable resource par excellence. While in absolute terms there is almost completely independent groundwater and disconnected from the natural water cycle, water moving at very different in the aquifers and sometimes travel great distances. When these waters are present in the subsurface for thousands of years and moving very slowly, are known as fossils and, as we shall see, can be exhausted.


Platelets, along with red blood cells and plasma, constitute a significant proportion in animal and human blood. Microscopically, thorns or barbed look like small ovals, and they can only be viewed by this means, since its average size is some four hundred thousandths of an inch (1-3.5 um). Platelets are fragments of bone marrow stem cells, also known as the megakaryocytes. Stimulated by the hormone thrombopoietin, platelets detach the megakaryocytes and enter the bloodstream, where they circulate for about 10 days before the end of his short life in the spleen. The thrombopoietin in healthy body, will help maintain the platelet count to a normal level, that is of approximately of 4.2 to 6.1 million of these cells tiny in two hundred thousand (1 ul) teaspoon of blood.

Platelets provide the hormones necessary for clotting and proteins. Collagen is released when the lining of a blood vessel is damaged. The platelets generate collagen and begin working on the blood clotting by forming a sort of Cap sealing any possible hemorrhage. A greater number outside of normal platelets, known as thrombocytosis, can cause serious health risks. Excess blood clotting can lead to the formation of blood clots that can cause a stroke. Conversely, a lower number than usual may lead to extensive bleeding. However, in some cases, lead to lower platelet number can be possible, for example, if a person has high sensitivity to movements or had heart surgery.

The number of platelets can be lowered by a daily intake of aspirin or other drugs that help reduce. While some disease or a genetic disorder can cause a reduced number of platelets, other times, they are exhausted because of a specific treatment or surgery. Burn victims, patients of organ transplant, marrow transplant patients, those receiving chemotherapy, and those who have undergone cardiac surgery often does not require blood transfusions, but do need transfusions of platelets.