system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it not possible to keep a decapitated human head alive?

Besides for the grotesqueness of a live decapitated head, what is the technical or medical reason that this is either impossible or never attempted.
I know that there were Russian experiments to keep dogs heads alive for some time, why never humans?
Assuming the high cost of doing such a thing was catered for (cost of experimentation is usually not an issue), I imagine the only technical limitation would be the complexity of the required mix of hormones produced by organs other than the brain. Blood can be oxygenated, warmed and cleaned by machines, and nutrition would not be a problem. What else would prevent this from working? I think I would rather lose my body if it was dying, and keep my head based senses, and mental faculty. It seems like such a waste to die if your body gives up. Currently there are thousands of quadriplegics who are maintained alive with a useless body either assisted by machine, or with the basic body functions to keep the brain alive, what difference if the body was removed?
gpt
You basically answered your own question, technically speaking. The body isn't just a blood pump, gas exchanger and glucose injector. Many aspects of body metabolism are dependent on things which don't happen in or near the brain, such as hormone synthesis and regulation. It is possible to keep a decapitated head alive, in a minimal sense, for a limited period of time, but long-term life support isn't possible.

So why don't we have a life support protocol for decapitation? Simple: There's no hope of recovery. It's not physically possible to anastomose the spinal cord; that is, once the spinal cord is severed, it's severed *forever.* It can't be patched up. Meaning once the head has been separated from the body, that individual — accident victim, let's say — has absolutely no hope of recovering from that injury. So such a protocol wouldn't actually do any good. It would just be, ethically and legally, mutilating a corpse.