Our bodies regenerate every year?

[RealityChuck]

No, the body regenerates when put under severe stress.

But you can only do it twelve times.

Oh, wait, you mean humans!

[Ed_Yong]

Guys, I think the definitive answers to these questions can probably be found in this article:

Your amazing regenerating body

My New Scientist subscription doesn’t seem to be working, so I can’t paste the text across. Grr. But I remember this being a good article that had a nice diagram showing how long each body part takes to renew itself. Can anyone get access?

[Exapno_Mapcase]

Sure.

HERE’S a question: how old are you? Think carefully before you reply. It’s a lot trickier than you might imagine. The correct answer, it turns out, is about 15 and a half. According to recent research, that’s the average age of your body - your muscles and guts, anyway. You might think that you have been around since the day you were born, but most of your body is a lot younger.

That may come as no surprise. It’s a common belief that the human body completely renews itself every seven years, and though biologists would hesitate to put a firm figure on it most are happy to accept that cells eventually wear out and are replaced. In some tissues - skin and blood - we know how long it takes, for example from seeing how long transfused blood cells last. Surprisingly, however, we have no idea how often most cell types are replaced, if indeed they are replaced at all. Until a few months ago it was impossible to tell. Experiments on mice had hinted that some cells are replaced more often than others, but no one was sure how relevant the findings were to humans.

Now neurologist Jonas Frisén of the Karolinska Institute in Stockholm, Sweden, has invented an ingenious technique for determining the age of adult cells.

…

The standard view from animal studies - and one man who agreed to have labelled nucleotides injected into his brain as he was dying from cancer - is that once the brain is formed, no new neurons are generated except in two areas: the hippocampus and a region around the ventricles.

Frisén first applied his new method to cells taken from the visual cortex. Here, as expected, the neurons turned out to be the same age as the person they came from - perhaps because they need to be wired up in a very stable way so that each time an object or colour is viewed it is perceived in the same way as before, he speculates. Cells in the cerebellum, which is involved in coordinating movement, turned out to be about 2.9 years younger on average than the person, which is consistent with the idea that this region continues to develop during infancy.

“We’ve now mapped the rest of the cortex and are well on our way with the hippocampus,” says Frisén. “So far, it doesn’t look like there are any new cells being formed in the cortex - they’re as old as you are. But some regions of the hippocampus are exciting - absolutely there’s neurogenesis.”

[solkoe]

Thanks for your interesting input.