system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If every cell in our body is replaced every 7 years, how do we retain scars and other signs of battle?

Furthermore, what about scars as children? Surely the body is growing fast enough to heal that up... What do I know though, I'm 5.
gpt
Your skin gets replaced by skin cells. Your hair gets replaced by hair cells. When you get a scar you have a wound. The wound gets filled by fixer cells. The fixer cells don't really have a purpose other than to fill in for the other cells that got damaged when you got the wound. So the cells that fix your scar on your arm aren't specific arm cells or the cells that fix your liver aren't liver cells. They are generic fixer cells. Because of that, when your cells are replaced, you get the same generic fixer cells to replace the scar cells.