YOUR TEMPORARY BODY

摘要

YOUR lifelong sense of self is intimately tied to your body, but how much of that body stays with you for life? The answer is surprisingly little. If you live to be, say, 75 years old, the vast majority of your body will be younger than "you" are. The cells lining your gut, for example, are replaced about every five days. The outer layer of your skin turns over every two weeks and you get a new set of red blood cells every four months. That is not so surprising given that these cells are on the frontline of wear and tear. But the rest of your body also needs a refit from time to time. Using a variant of carbon dating, a team led by Jonas Frisen at the Karolinska Institute in Stockholm, Sweden, have discovered that the average age of a bone cell is 10 years, a muscle cell 15 years and a fat cell about 9.5 years. Your heart cells are on average six years younger than you; if you live beyond 50 about half of the cells in your heart will have been replaced.