We often think of bones as non-living, concrete-like substances that have little to do other than support us. But bones are alive-as much as any other tissue in the body. And they are integral to our overall health.. Blood cells are manufactured in bone marrow,. which makes bones just as important to body function as they are to body structure: our heart, lungs, kidneys, muscles, and everything else need a constant supply of healthy blood. Bones also act as holding places for essential chemical elements. Excess nutrients are either excreted in the urine or deposited on the bones. When the body has ¬a-shortage of a particular nutrient,-it can draw upon the bones to replenish its stores, sending the nutrient where it is needed most. The minerals calcium, phosphorus, and magnesium, for example, are stored in the bones in large quantities. On average, our bones contain about 1.4 kilograms of calcium, 68o milligrams of phosphorus, and 25 milligrams of magnesium. Almost 99 percent of the body's calcium is found in the bones.