Humans and most of the animals are supported by a structure chiefly consist of Bones. This structure, as we all know, is called Skeleton. There are round about 200 distinct bones present in the Body. This number does not include many small bones found in tendon of muscles and in the ear.

Apart from this, the number of bones varies at different periods of life. For instance, the number of bones in children are more than in adults. This is on account of the fact that some bones which are separate in childhood, becomes united when they are grown.

Chemical Composition of Bones:

The main physical properties of bones are their hardness, toughness and elasticity. Their strength can be judged from the fact that one cubic inch of compact bone is able to support a load of 5000 pounds.

Bone is mainly composed of two basic elements:

1. Earthy or Mineral matter (mainly lime salts) – which provides hardness
2. Animal matter ( mainly Gelatin) – which provides flexibility

Proportion of mineral to animal matter again varies with Age. For instance, in infants, the bones are chiefly composed of animal matter.  That is why, their bones are rarely broken, although have great tendency to get bent. Care should always be taken, not to allow babies to walk at too early stage of their life. This seemingly silly mistake, can cause a child to pay a huge price for it, for whole of his life. With the passage of time, the proportion of mineral matter increases. And because of this, the flexibility of the body goes down as age goes up.

Covering of the Bones:

A fresh and living bone is always covered with a delicate, fibrous and tough membrane called Peristeum. This membrane adheres very closely to bones and covers every part except at Joints. Joints are protected by other covering called Cartilage. Blood supply of bones mainly takes place in this particular membrane. That is why, this membrane is very important in keeping the bones in good health. If the portion of this membrane is detached by injury or disease, then the bone portion beneath it would be under great risk. Eventually the bone from that place loses its vitality, and become a weak link of the bone.

The Bones in the Body are placed in such a manner so as to render a wonderful service in terms of strength, firmness, protection of soft tissues and organs. Beyond this, bones are excellent levers for the muscles to act upon.