Asked in Genetics
Why are stomach cells replaced every 2 days and red blood cells replaced every 120 days?
Your stomach cells are exposed to the harsh stomach acids, if they were not replaced as rapidly as they are the stomach acid would not be able to be contained thus digesting itself and exposing the rest of your body to the acid.
As for the red blood cells our body can only replace about 1% of them per day, essentially there are around 20-30 trillion red blood cells in your body, replacing 200-300 billion cells that are so vital is no easy task. But its easy to assume that only a fraction are replaced every day to use each cell to its fullest life before recycling it.
On a side note every 7 years your a totally new you with 100% new cells.