The human body replaces itself with a largely new set of cells every seven years to 10 years, and some of our most important parts are revamped even more rapidly.
Every individual cells have a finite life span
When they die off they are replaced with new cells. There are between 50 and 75 trillion cells in the body. Each type of cell has its own life span, and when a human dies it may take hours or day before all the cells in the body die.
Organs like lining of your stomach and intestines, are renewed much faster. Due to constant wear and tear from the process of digestion, these cells have an average lifespan of just 5 days.
Red blood cells live for about four months, while white blood cells live on average more than a year. Skin cells live about two or three weeks. Colon cells have it rough: They die off after about four days. Sperm cells have a life span of only about three days, while neurons typically last an entire lifetime.
If a neuron in the brain happens to be destroyed the brain repairs the damage by reprogramming itself to bypass the destroyed neuron.
Because neurons in the brain are never replaced people retain their personality for as long as their brain continues to function normally.
There’s nothing special or significant about a seven-year cycle, since cells are dying and being replaced all the time. It’s not clear where this myth began.
That myth has been circulating since the 1970s, and was thrown into a scientific paper until very recently.