The Development of Cancer
Cancer Research UK
Body tissues grow by increasing the number of cells that make them up. The cells reproduce themselves exactly. One cell doubles by dividing into two. Two cells become four and so on.
This happens very fast between conception and adulthood. But once we are grown up, most cells only reproduce in order to replace others that have died, for example through injury or illness. Some cells carry on reproducing. These include sperm cells, hair cells, cells in the gut and cells that make blood in the bone marrow.
Not all cells carry on being able to reproduce. Most cells mature and become specialised for their particular job in the body. Mature cells may lose the ability to reproduce as they develop. But there will always be enough immature cells around (called stem cells) to replace cells that are damaged or killed... More Information