All the vital organs and tissue regenerate over time.
Pancreas regeneration takes 24 hours, the Stomach a week, blood is replaced regularly, and the brain creates new connection. It is believed that every cell in your body is replaced in roughly 7 years, and on average human the body is 15 years old. With time and pollution, even gravity itself falters the cycle, new cells are not as stable and organs become more open to diseases. Waste accumulates until eventually proves fatal. If you grow a body in a tube, under perfect condition it is believed to function for 190 years.
The world’s verified oldest person is Jeanne Calment 1875 -1997, aged 122 years and 164 days.
However Antisa Khvichava from Georgia is said to have been born 1880 and 130 years old.
Here is a link – http://uk.news.yahoo.com/4/20100310/video/vwl-woman-about-to-turn130-15af341.html
If this proves to be right she will be the oldest person in modern recorded history.
Basically if you have good genes, avoid polluted areas and live a good healthy lifestyle it’s possible to live up to great age.