Why Can’t Humans Regrow Body Parts?
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Why Can’t Humans Regrow Body Parts?

September 1, 2019

Hey there and welcome to Life Noggin, Have you ever wondered if it was possible
for humans to regrow body parts? Why is it that when a person loses an arm,
only the wound is healed rather than the body regrowing their lost limb? In the spirit of Dr. Connors, let’s find
out. I just hope we don’t all turn into Spider-Man
villains. So humans can’t regrow their own limbs,
right? Well, that may not be entirely true. As an embryo, long before your birth, you
may have had the ability to replace your developing limbs. Through scientific surgery, researchers have
shown that at the embryonic stage of development, frogs can regenerate their developing limbs. This has even been shown in mice, which like
humans, are mammals. It is yet to be proven the same with human
embryos, but with this evidence, the theory is that vertebrate embryos, including humans,
can regenerate their limbs if they are damaged or amputated. However, other than a few special and small
cases like the regeneration of fingertips, humans don’t really have this ability after
birth. But do any other animals? It just so happens that salamanders have this
super awesome superpower! They are the only vertebrate that can regrow
their limbs and many other body parts throughout their lifetime. In fact the axolotl, a Mexican salamander,
can regenerate almost anything; from their eyes, to their spinal cord, to even parts
of their /brain/. These adorable little guys are amazing! I want 20 of them. So how do salamanders do it? Well, when a human losses a limb, their cells
close the wound and a blood clot forms. This leads to a scab over the wound and an
eventual scar in the place of where the limb was. But for a salamander, scar tissue never forms;
a striking difference between their regeneration and human wound healing. A salamander’s wound closes more rapidly
and cells rush to the amputation site. These cells revert back to a less specialized
state and begin creating the blastema, which is the bud of a new limb. As the blastema grows, it begins to form the
outline of the new limb and the foot. The cells begin creating new tissues by proliferating
and differentiating into things like muscle and bone. The new leg lengthens, filling out the missing
segments between the amputation site and the toes. The whole process usually lasts around two
months, and then the salamander has a fully regenerated limb. Perfect for a high five! But in humans, that blastema never grows. Some scientists think that’s because humans
don’t have all the genes necessary to facilitate such a level of regeneration. But others think that humans don’t have
this regenerative ability because it might make them more likely to develop cancers. But even if humans could regrow their limbs,
there still might be an issue. Let’s take a look back at that adorable
little axolotl with the findings of two recent studies. The researchers found that, like biological
wrecking balls, certain jumping genes need to be shackled in the axolotl’s cells or
they might disrupt their process of regeneration. They discovered that proteins found within
the little water monsters allow them to prevent these jumping genes from causing havoc. So, regeneration is really complicated and
maybe for right now, humans can’t regrow their limbs. But these studies at least give scientists
hope that we could learn better methods for treating human conditions, like wound healing
and regenerating simple tissues. Hey, even becoming just a little bit more
like Wolverine would be awesome! I’m Blocko, and I’m the best at science
communication. And i have claws. So what do you think? What limitations of humanity would you want
science to be able to overcome? Let me know in the comments below! Make sure you come back every Monday for a
brand new video. As always, I’m Blocko and this has been
Life Noggin. Don’t forget to keep on thinking!

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  1. Growing an entire limb
    For a limb to regenerate, you need bone, muscle, blood vessels and nerves. There are adult stem cells, a kind of undifferentiated cell that can become specialized, that regenerate muscle, but they don't seem to activate. "You can regenerate blood vessels and even nerves," Gardiner said.

  2. tbh humans too op since we human players been griefing and trolling other species players so the Dev worked on us to minimize the exploits.

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