Blood stem cells are stem cells pro­du­ced in the bone mar­row. They are the star­ting point for
the crea­ti­on of all new cells of the blood and immu­ne sys­tem: They can deve­lop into red and
white blood cells and plate­lets. Once the matu­ra­ti­on pro­cess is com­ple­te they lea­ve the bone
mar­row and enter the bloo­d­stream, whe­re they per­form their job as spe­cia­li­zed cells.
Depen­ding on their func­tion, the blood cells die after a few days or mon­ths and are therefore
con­stant­ly repla­ced by new cells.