system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How you can survive getting a limb blown off, but if a main artery gets cut you bleed out and die.
gpt
It all depends on how quickly you gain medical attention, the size of your blood vessels, stress of the patient, and where exactly you get hit.

Your body has actually evolved to automatically retract your blood vessels to shunt off the flow of bloo if you are missing a limb, but a cut in one of your vessels doesn't allow them to retract into the body so that you'll quit bleeding out.