I'm not the man I used to be...

June 8, 2009 11:45 AM

How long will it does it take for all the cells in my body to die then regenerate? The question I am really asking is from a specific point, say, NOW, how long will it be before my physical body is composed of a completely new set of cells?
posted by sam and rufus to science & nature (13 comments total)

Never. Nerves don't regenerate. The nerves you have date from when you were six months old.
posted by Chocolate Pickle at 11:47 AM on June 8

Depends on which part you're talking about. Most neurons do not regenerate, for instance.
posted by mr_roboto at 11:47 AM on June 8

This person says that the common wisdom is seven years. She goes on to trace the history of that common wisdom, adds quite a bit of information about cell regeneration for different types of cells (for example, average age of non-epithelial intestinal tissue is almost 16 years), and then concludes that it's plausible that the average time could be seven years. She has references at the end.
posted by Houstonian at 11:52 AM on June 8

Here's a fairly thorough answer. I am not a biologist so I can't verify its authority, but there are journal references at the bottom.
posted by desjardins at 11:52 AM on June 8

There's an old estimate of about 7 years for the whole body to regenerate, but that's on a *molecular* level. On cellular level, some cells turn over fast, some slow, some not at all.
posted by originalname37 at 11:55 AM on June 8

Yeah, you're going to want to be careful with your terms. As has been pointed out, certain cells, neurons but also cardiac muscle, basically never divide. The cells in your heart when you die are numerically identical to the ones you had in your heart when you were born. There are more when you're an adult than when you're a kid, but that's just because you've grown. The cells themselves are not replaced. Same goes for nerves.

But if you're interested in continuity of specific atoms, that turns over about every seven-odd years. Even a cell which is never replaced will be constantly replacing parts of itself. Links provided above will get at that idea.
posted by valkyryn at 12:35 PM on June 8

Neurons regenerate. Just very slowly.
posted by kldickson at 12:45 PM on June 8

All very, very interesting.
Thank you very much.
posted by sam and rufus at 12:47 PM on June 8

I can't speak for the CNS, but I did have a doctor that always reminded me that all the cells in a skeleton are replaced every 2 years. Thats a big chunk of you, so it will at least provide a MINIMUM.
posted by hal_c_on at 2:02 PM on June 8

Previously.

I'll repost my answer from that question:

"New" is a misleading term, because every new cell is just half of a bulked-up old one. When a cell divides, which one is new and which one is old? Are they both new?

Since every cell you have is derived from one progenitor cell, (created from the fusion of sperm and egg) no cell is ever really 'new'.

I suspect that looking at the question in terms of molecular turnover is slightly more interesting, but exceedingly difficult to quantify.

In areas exposed to the outside world, like your gut and your skin, the distinction can often be made a little more clearly. When the progenitors of skin cells divide, one gets pushed upwards towards the surface and differentiates, while the other remains behind and continues to grow and divide.

posted by chrisamiller at 2:36 PM on June 8

The lining of the stomach regenerates very rapidly, because the part of it that's exposed to food is being digested away constantly.

Neurons regenerate. Just very slowly.

Depends on what you mean by "regenerate". A nerve with a myelin sheath where the axon gets severed can reconnect. But nerve cells stop dividing and reproducing at about age 6 months.

It has to be that way, because the details of neuron interconnect is the most important thing about them. If a neuron divided, what would that do to the interconnection topology?
posted by Chocolate Pickle at 3:20 PM on June 8

If you're lucky, those teeth of yours will be the same dentine when you die as they are right now.

Tattoos don't change at all either.
posted by Jilder at 4:39 PM on June 8

The lining of the stomach regenerates very rapidly, because the part of it that's exposed to food is being digested away constantly.

No it's not. The gut lining does slough off for various reasons (it's a defence mechanism for example) and is a normal physiological process, but in a healthy person it's not digested. There's a thick mucus lining along the entire GI tract making sure that doesn't happen.
posted by shelleycat at 6:10 PM on June 8