system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why do we get a bump on our head when we bang it against something but nowhere else on the body?
gpt
Easiest way to put it is there’s no padding/fat. You can get bumps on other parts but it would take a more severe hit. When you get injured blood rushes towards it. Think of it like plugging a dam. Now picture the dam is your fat. Now if you take the dam away and it starts to pour rain aka a head injury the blood still rushes there but now it’s trying to act as a damn. By doing this the body tries to go into a survival mode and it typically adds a calcium like layer which is usually the bump on the head.