system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do they re-attach severed limbs?

How do they re-attach severed limbs in surgery? Also, if you just physically reattach your severed finger by securing it with tape/stitches, would your finger reattach itself?
gpt
When body parts are reattached, the most important thing to get right is blood flow.

The arteries and veins are all reconnected as best as possible.  This is needed to keep the part alive.

Muscles and nerves are also reconnected to give you sensation and movement.

The skin is the last to be reconnected.

If you just taped a finger tip in place, it wouldn't have the blood flow, and just die.