The human body is self-repairing and self-replenishing. According to one estimate, almost 200 billion cells die each hour. In a healthy body, dying cells are simultaneously replaced by new cells.
||Length of Time
|Red blood cells
||Over 1 year
|Other white blood cells
*Brain cells are the only cells that do not divide further during a person’s lifetime. They either last the entire lifetime or, if a cell in the nervous system dies, it is not replaced.