system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If we make skin and muscle cells when we heal cuts and heal/generate bones after breaking them, why wouldn't we be able to grow a finger if one is cut off?
gpt
Our body heals like a blind handyman repairing a house.

If a ball crashes through a window, you call up the blind handyman and they feel around the impact. Glass shards. Window frame. Must be a broken window so that can be fixed completely by ordering a new window.

One day a car dries through the wall, taking out the entire window frame. After everything is cleaned up, you call up the blind handyman. However, they only feel the large hole in the wall and has no idea there used to be a window. The best and quickest thing they can do is seal up the hole to prevent things outside from getting in and things inside from getting out (scar).

Our body heals based on the surrounding tissues near the wound. If it can't figure out what was there or if the wound is too large, it becomes a scar.