Microscopically, cortical bone looks like concentric rings. Cancellous bone resembles latticework and is spongy. A system of blood vessels supplies the bones with needed nutrition. Bones serve as storehouses for minerals and fats. Approximately a quarter of a bone's weight is fluid.
Minerals make up the remaining weight along with other nutrients.
The semi soft center of the bone contains marrow. Marrow is similar to a busy factory manufacturing red blood cells, which are necessary to adequately distribute oxygen throughout the body. Throughout a person's lifetime, bone continuously breaks down and rebuilds itself. Sometime after the age of 50, bone naturally begins to lose strength. This loss may progress due to decreased demands placed on the skeletal system.