Body renews itself every seven years

[snopes]

Comment: I know I read an article about whether the physical body is
completely new every 7 years or so, because all of our cells have a
lifespan shorter than that except some neurons.

[Insensible Crier]

House M.D. uses this information in one of its episodes in the first season. I know. It's a completely reliable source and verifies everything. Case solved.

[snapdragonfly]

Well, I guess that depends on how specific and accurate you want to be. I know that some cells renew much faster than that - for example the esophageal and stomach lining turns over very quickly, in just a few days, IIRC they need to be able to reproduce so quickly because of the acid in the stomach. That's also why esophageal cancer is usually too far gone by the time they catch it, because the cells turn over so fast and therefore any cancerous changes are reproduced at a really fast rate. (I found out about all this stuff when I was researching my acid reflux disease.)

I don't know which parts of the body take seven years to completely regenerate. I assume this number is just an average. It takes about, what, 6 months to grow out your nails? So you'd have new toe and finger nails in under a year.

[Flagg]

I got my first tattoo in 1994. If this UL were true, wouldn't it be long gone by now?

[compass]

Originally Posted by Flagg

I got my first tattoo in 1994. If this UL were true, wouldn't it be long gone by now?

Please somebody explain this! How does the ink manage to stay there? Where exactly is it anyway? How come scar tissue over tattooing loses colour?

But anyway, aren't there things which can be permanently absorbed? Stuff like heavy metals which can't be excreted? Or does that not count as part of the body?

Is the rising inflection the most annoying in the world?

Compass (points to Birmingham)

[TripleAAA]

I've heard of your body changing every 7 years. But if new cells restore themselves, wouldn't scars and tattoo's (as Flagg said) be gone?

[Jahungo]

The OP is false, according to this, since there are several classes of cells which basically last a lifetime.

As for tattoos, there is rapid turnover of cells in the epidermis (the very outside layer of skin), but the tattoo ink actually goes a bit into the skin in the dermis, according to this. The ink is insoluble in water, so it doesn't move much in the aqueous environment in the body. It doesn't say in the article, but I doubt the ink is actually within individual cells. I'd bet that the ink droplets within the skin are far larger than the skin cells themselves, and stay in place while cells die, divide and migrate around them.

[ganzfeld]

Originally Posted by Insensible Crier

House M.D. uses this information in one of its episodes in the first season.

I thought it just mentioned cell regeneration. I don't recall anything about seven years. Any House fans remember the episode?

[Salamander]

Originally Posted by ganzfeld

I thought it just mentioned cell regeneration. I don't recall anything about seven years. Any House fans remember the episode?

Not well enough to recall the episode name for reference... but yes, I recall the episode. I can't verify that the "whole body is replaced every 7 years" was used but the fact that various internal organs are "refreshed" at varying rates was used to describe why the patient was suffering from a chain of supposedly unrelated symptoms.

I took a quick glance at the episode guide in Wikipedia but I couldn't find it... I'm pretty sure it happens within the first 3 seasons though.