I know that our bodies have a mechanism for replacing dead cells with live ones. And that numerous parts of the body ‘grow back’ if removed.
So why do so many poor fellow men lose hair (in an ugly manner too)? why have I lost all nasal hair? Why does eyesight and hearing deteriorate? Why, with the amazing ability of cells to replicate and replace old with new, do we grow old and die?
Other than the nails…what lost body parts do humans have that grow back?
Most of the adult human body is only a few years old. The whole lot is regrown cells from what we eat.
By ‘lost body parts’ I mean the cells that die or get taken away by small injuries such as cuts and grazes on the skin. I realize that losing a whole arm does not result in an arm growing back.
There’s a huge difference between cells dividing to replace dying cells and the regeneration of a whole limb or organ. The latter would require coordination between a whole lot of cells from a whole lot of cell types. Say you lose an arm. Or even just a finger. You’d have to regenerate bone, nerves, blood vessels, muscle, connective tissue, skin, etc, etc. That’s hugely different than having some epithelial cells in your gut lining constantly sloughing off and replenishing. Our healing system is designed to just close up any gaps as quickly as possible.
The liver can grow back:
This article is a pretty good discussion on the topic
I found it an interesting read anyway.