There are normally 206 bones in the human body, forming the skeleton . Bones support all parts of the body and protect the brain and organs of the chest. Bones of the leg can be nearly two feet long, but the tiny bones of the middle ear are less than an eighth of an inch long, with the rest of the skeleton in between in size. The main function of the bones is to provide support and protection, but bones also have other vital functions. They are part of the circulatory system for example, since a soft material inside of long bones, called red marrow, produces the body's blood cells.
Bones are also part of the hormonal system .
They are an important reservoir for minerals such as calcium. If the body's intake of the mineral calcium is too low, the bones release some of the calcium that is the main mineral in bone to make up the deficit. The loss of calcium weakens bones, however, making them more easily breakable. Various diseases that affect bones are discussed in more detail in Bone diseases . Other bone diseases and more information may be found by using the 'see also' references below.