WEBVTT - BrainStuff Classics: Does the Human Body Really Replace Itself Every 7 Years?

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<v Speaker 1>Welcome to brain Stuff production of I Heart Radio. Hey

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<v Speaker 1>brain Stuff, I'm more in vocal Bomb and today's episode

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<v Speaker 1>is another classic from our former host, Christian Sader. This

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<v Speaker 1>one addresses one of those science things that we hear

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<v Speaker 1>all the time, and we wondered whether it's true. Does

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<v Speaker 1>the human body really replace itself every seven years? Hey,

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<v Speaker 1>brain Stuff, it's Christian Sager. Today's question does your body

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<v Speaker 1>really replace itself every seven years? The short answer is no,

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<v Speaker 1>But don't worry. This isn't a case of Chicanerius researchers

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<v Speaker 1>pulling the wool of shoddy science over your eyes. Your

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<v Speaker 1>body mostly replaces itself every seven to fifteen years. Some

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<v Speaker 1>bits are never replaced. Others, like the lining of your

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<v Speaker 1>stomach and intestines, are renewed much faster due to constant

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<v Speaker 1>wear and tear from the process of digestion. These cells

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<v Speaker 1>have an average lifespan of just five days. Yes, the

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<v Speaker 1>organs that work the hardest have the fastest change over.

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<v Speaker 1>You get a whole new skin every two to four weeks,

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<v Speaker 1>and your red blood cells last less than half a year.

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<v Speaker 1>That's not bad considering that they're route through your circulatory

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<v Speaker 1>system is about a thousand miles. The average American car

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<v Speaker 1>doesn't even travel that far, and your liver renews itself

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<v Speaker 1>at least once every couple of years. As the human

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<v Speaker 1>bodies detoxifier, it goes through a lot. Other tissues take

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<v Speaker 1>longer to completely replenish themselves, like your bones. For instance.

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<v Speaker 1>Skeletal cells die and new ones grow constantly, but the

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<v Speaker 1>complete process takes about ten years, and the process slows

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<v Speaker 1>down as we get older, which is why our bones

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<v Speaker 1>tend to get weaker as we age. And like I said,

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<v Speaker 1>some parts of your body stay with you for life.

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<v Speaker 1>The cells of the ner lens of your eye formed

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<v Speaker 1>when you were just an embryo. Your tooth enamel wears

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<v Speaker 1>down with use, never to return, and evidence indicates that

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<v Speaker 1>you can't regrow the neurons of your cerebral cortex. It's

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<v Speaker 1>loss can lead to diseases like dementia. Luckily, other parts

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<v Speaker 1>of your brain do regenerate, like the hippocampus, which helps

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<v Speaker 1>us create memories, and the olive factory bulb, which helps

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<v Speaker 1>us smell. So how do we know all this? Well,

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<v Speaker 1>it turns out it's thanks to our old pal nuclear

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<v Speaker 1>weapons testing high fives for radioactive stuff being released into

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<v Speaker 1>the atmosphere no really above ground. Nuclear detonations during World

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<v Speaker 1>War Two and the Cold War spiked Earth's air supply

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<v Speaker 1>with extra carbon fourteen. It's been declining back toward the

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<v Speaker 1>norm at a predictable rate since the nineteen sixties, which

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<v Speaker 1>means that you can use the amount of it present

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<v Speaker 1>in any given tissue, sayful, to determine when those cells

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<v Speaker 1>were born. More carbon fourteen means older cells. Today's episode

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<v Speaker 1>was written by me and produced by Tyler Clain. Brain

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<v Speaker 1>Stuff is production of I Heart Radios How Stuff Works.

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<v Speaker 1>For more in this and lots of other replenishing topics,

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<v Speaker 1>visit our home Planet has to Works dot com and

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<v Speaker 1>for more podcasts for my heart Radio, visit the iHeart

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<v Speaker 1>Radio app, Apple Podcasts, or wherever you listen to your

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<v Speaker 1>favorite shows.