system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When a person gets one of their appendages amputated, how does the blood get back to the heart?

Do they have to attached the blood vessels together? How did they do this in like the wild west or back in the late 1700's?
gpt
Blood doesn't rush around your body in one big tube.  What happens is the blood vessels split and become thinner and thinner.  Think of a fan where the bottom is the main artery which splits into finer tubes called capillaries. 

This splitting happens all through your skin, so there are millions of very fine capillaries covering your body.  Once the cells have taken the oxygen from the blood through the walls of the capillaries and given up the waste products back into the blood,  then the capillaries then all join back up again into veins and travels back to the heart. 

So,  when you chop off an arm some of the fine capillaries are lost but the vast majority are still there. The amount of blood and the pressure of the blood get messed up for a while,  but the circuit still exists.