system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why can humans regrow things like skin and muscle but not organs like eyes and kidneys?
gpt
I think you're confusing how skin and muscle *heal*, with *regrow*. 

Your organs heal on a daily basis from natural cell death and the toxins you ingest or are exposed to (such as alcohol), just like how your skin and muscle heal. But if you remove a muscle from the body, like if you removed a kidney, neither of them are going to regrow. 

Your skin doesn't regrow easily - scars don't count as regrowing. Scars are basically the body saying "We can't regrow the original skin, use scar tissue to plug up the wound." like putting a poster over a hole in a wall.