What if someone were sitting exactly upright and a super thin, super sharp blade cut all the way through their neck? The blade is so fine that it does not disturb the surrounding tissues at all, so the arteries and veins and trachea and stuff are still all lined up. Assume that there is support provided so that the head and body never shift from the muscles being severed. I’m assuming paralyzation from the neck down from the nerves being disconnected, but would you die, if nothing knocked you over? What if you were just cut to the bone and the spinal cord was not severed, but all the fleshy bits were? Would stuff just seal itself back together eventually?
Arterial pressure would cause massive bleeding.
ETA: the temporary paralysis would include breathing.
Wouldn’t the artery be effectively sealed by the pressure of the head itself?
Yeah, the breathing thing would be an issue…
On the other hand, there is such a thing as internal decapitation, where the bones separate, but the rest of the connections between head and body remain intact. It’s apparently survivable.
Wouldn’t work.
The carotid arteries are under significant pressure to pump large of volumes of blood through your brain. Even a weakening, let alone a complete separation, of the arterial walls can cause a dissection.
Nerves also won’t conduct once you disrupt their cell membrane, so, paralysis will also kill you.
Any motion would cause disruption. However small, the heartbeat does cause a little bit of bouncing inside the body. Breathing causes even more motion, assuming you’re still breathing at all at that point. And you’d have to. Repair time takes more than a minute or two. Run water through a garden hose. Not high pressure, just a small dribble. Have somebody hold it so they can keep both parts completely still. And then slice the hose completely through. Even with the sharpest scalpel you could find, you’ll see that water still leaks substantially through the slice, no matter how hard you try to hold the hose together. So you’d have internal hemorrhaging and that can’t be a good thing.
How much does your head weigh? Certainly not heavy enough to apply enough pressure to stop carotid arterial bleeding.
Almost forgot. When suffering any kind of trauma, even slight, the body goes into some level of shock almost instantaneously. I had a heavy piece of plate glass come down and slice open the back of my wrist. There was no pain that I was aware of, just the pressure of the glass. Looking at it, there was little blood, no more so than you would expect of a paper cut. I figured it was just something that needed a bandage to close the wound. It was everyone around me who insisted that I allow them to take me to a hospital. Even though I couldn’t see myself, they said I had turned almost bloodless in my face, I was so pale. Within just a few minutes, I became weak and unsteady.
I figure all the severed arteries, veins, nerve endings, and muscles couldn’t possibly repair themselves fast enough to prevent someone from keeling over and literally losing their head, so to speak. (My wrist took over a week just to heal enough to remove the stitches and continue repairing itself internally.)