When a piece of skin, muscle, bone, nails, or hair gets removed or damaged, those usually grow back like nothing happened. So, why isn’t it possible for hands, or even something smaller like a finger to regrow? Or would a piece of meat just regrow there instead of something useful?
In: 563
actually in many cases bone, muscle, and even skin can’t regrow properly.
simple example: a skin scar is visible because it’s a different type of tissue, specifically connective tissue, which is weaker than normal epidermis in many ways.
more in general: as we grow up in the womb, our body parts are built starting from a mass of all-same “stem cells”. Stem cells *differentiate* into other types of cells in a very organized, multi-step process that takes place mostly in the womb. We are born with some niches (small groups) of partially-stem cells (= some steps before the final one in the differentiation) in some parts of the body, but mostly we can only regenerate wounds by making more of the types that are already around the wound.
To make a hand, you would need the cells to “know” that they have to make only this many cm of bone, then build an articulation, then another shorter bone, another articulation, all the muscles and tendons and nerves required to control them, and finally a nail. It’s extremely complex and the cells don’tknowhow to do it anymore.
Axolotl and a few other species can do it and we still don’t know how they do.
Latest Answers