system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If all the cells in our body are replaced every ~month. Why do we keep things like scars and wrinkles if they're not in our DNA?
gpt
Scar is formed of extracellular collagen, ie outside the cells.  When people say that cells are replaced every month this is true, but the extracellular components are not changed and the scaffolding stays the same, ie the scars remain even though the cells are replaced.  In ELI 5 terms, think of an apartment.  Even though a new family may move into the residence every month,  the building itself remains the same.