Bones serve us in many ways. They help us to move. They provide support when we are standing or sitting. They even protect organs of the body such as the brain, heart and lungs. They also produce red and white blood cells and store minerals. That means bones are very important, so we must take very go care of them.
Bones are stong and hard, and come in many shapes. Bones have a hard outer layer called the compact bone. This outer layer makes up about 80% of the total bone mass of an adult skeleton. This layer gives the bone its white color. The inside of the bone is called cancellous or spongy bone. Although the cancellous tissue makes up only remaining 20% of the total bone mass, it is light and porous, and makes up most of the bone material. The cancellous tissue also has space for blood vessels and marrow.
Bone marrow, in the medullary canal of long bones, produces blood cells in a process called haematopoiesis. New red and white blood cells are produced every day to maintain constant blood levels.