system
Given the following post, respond as if you're commenting on Reddit:
human
If someone loses a part of their body that can be reattached, how do all of the nerves/veins/tendons etc. Find their way back to each other?
gpt
Replantation or limb reattachment via surgery is microsurgery, therefore requires a microscope to operate under. 

With such surgery often the route of reconnecting the various vessels to each other is done manually. This takes many hours 'under the knife'. 

Usually when people ask this question they're thinking about 'vascular remodeling', where after an amputation the blood vessels reorganize themselves to restore proper blood flow. 

With reattachment of limbs this process must not occur, otherwise the severed limb would merely be a dead limb sewn on. Hence the manual reconnection.