How Much of Your Body Is New Every Year? | Compilation

My body's been trying to get rid of me for 72 years ☹️

"Regrowing your liver isn't as great as it sounds" -Prometheus

The reason we are bad at regenerating lungs, is because for most of our evolution these injuries were almost entirely fatal. The same is true for brains and hearts etc. If an injury is always lethal, there is no selective pressure to regenerate it, and regenerative mechanisms get lost over time. The very fact we can live without a spleen is probably why it regenerates so well - it is non-essential but its presence confers a selective advantage. Likewise you wouldn't last a day without your liver, but you could last a long time with maybe 20% of your liver. You can also think about how a small animal like a salamander with a low metabolism and low flow blood rate would be more likely to survive losing a leg than a human or a frog. The salamander can still slide along on its belly, while the human will bleed out and the frog will become immediately vulnerable if it doesn't also bleed out - and surprise, salamanders regenerate legs, humans and adult frogs do not. Fish and salamanders can survive some pretty major heart injuries that would kill a human in seconds (probably because their metabolisms and oxygen flux are very low compared to mammals), AND they can regenerate their hearts. I don't think this is a coincidence. This sort of removal of selective pressure is commonly used to explain many phenomena in nature, such as the fact that many rodents age rapidly and are super vulnerable to cancer because most of them die to predation before these pressures become relevant. Of course the truth is way more complicated this. For example, traumatic liver and spleen injuries that don't also destroy other critical systems are pretty rare, suggesting that maybe these mechanisms are retained because of damage from disease or toxins, or because they are pleitropically linked to developmental and regenerative processes that are under stronger selective pressure. The liver, and other organs also adjust their size (slightly) to reflect demand as part of homeostasis, so regeneration of the liver and spleen might be linked to that. I'm just one regenerative biologist with an opinion, many others would disagree with me, and that's ok, it's how science should work. A bit of shameless self promotion, my thoughts on regenerative evolution are here: https://www.frontiersin.org/articles/10.3389/fcell.2023.1206157/full Some other citations: Why slow metabolism vertebrates are better at regeneration https://pubmed.ncbi.nlm.nih.gov/32914411/ Regeneration of organs as an extension of homeostatic processes https://pubmed.ncbi.nlm.nih.gov/22542702/

"Eager beavers"...someone on the team is VERY pleased with that line 😂

How long till I get a new lower back?

14:04 Was the rat who regrew his liver 12 times named Prometheus? 🐀

Thank you for all the wonderful and informative videos, it’s been a fantastic 2023. Here’s to another year of amazing science videos!

still a good video... but, I was kind of hoping this video would be about all the cellular turnover in a given year. Such as how many new skin cells, how many new cells in your stomach lining and just a grand total somehow of all the cells that the body replaces, on average, in a given year for an adult.

Thanks to all the scientists working on this and special thanks to the scientific uteruses letting humanity put their old decorations to use.

Accessory Spleen sounds like a good band name

"Monthly redecorating" 😆😆😆

Please tell me the rat in that liver study was called Prometheus

You know that famous paradox where if you repair a boat over time until eventually every single part has been replaced with new parts, is it still the original boat? And what if you made another boat out of all of the old parts from the original, is considered that a new boat or is that the original boat? The fact that you're still you after all these years of living and your body replacing parts leads me to believe the boat is still the same boat even if its parts get changed.

I’m almost 80 but my hair stayed the same color as when I was 18. I’ve a few of those wild curly grey eyebrows and plenty of age-appropriate wrinkles but no grey hair. Weird.

To be fair, no known regeneration on earth is infinite. Even the axolotl, the creature with the best regeneration on earth that is capable of regenerating nearly half its brain, will lose the ability to restore its limbs after they have been severed enough times. Each time their regrown it becomes a little less efficient and perfect as if part of the code is lost.

I started turning grey at 17. I liked how it was growing in, plus it has more body than the original.

VICTIMS OF ABUSE... Just think, one day, your attacker would have never touched a single cell of you. i find that healing <3

So glad sci show dropped the all caps style… used to never be able to read them

I figure a lot of people would volunteer for liposuction if it was paid for, lol.

Happy new year!