How can embryos grow bones, organs and limbs, but once they pop out they can’t anymore?

Question

I mean like, e.g why can’t we grow back a limb we already grew at one point while we were in our mother’s womb?

In: 1

Answer 1

Embryos are comprised of a special kind of cell called a pluripotent stem cell. This means those cells are capable of differentiating into any kind of cell in your body. Once your cells have differentiated (become a skin cell, or muscle cell, or bone cell) they remain that kind of cell. Organisms that can regrow limbs have the ability to stimulate cells to revert back into their undifferentiated state, allowing them to become the type of cells necessary to regrow the limb. Unfortunately, humans do not have this ability, although scientists are working on methods to induce this effect artificially.

In fact, we’ve already successfully mastered the process of reverting human cells back into pluripotent stem cells in the lab! This is still a long way from being achieved in vivo (in a living organism), but we are making significant progress in that direction.