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Emily_Ge t1_ixlpuf6 wrote

Reply to comment by Entheosparks in If freezing tissue generally damages the cells, how are we able to freeze human eggs and embryos for birthing later? by badblackguy

And at some point, there is no way to physically freeze something fast enough. Because the rate at which the heat is ‚sucked‘ out of a body, is dependent on the distance it has to travel.

Even if you replace a humans blood with glycerine and do everything you can to inhibit crystal formation: there‘d still be too large distances, and you‘d cause damage.

Not to mention the brain being extremely sensitive to cell loss.

And even when freezing embryos like in your example: some won‘t be able to be revived.

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RationalFragile t1_ixm7f0i wrote

But, the blood system in warm blooded animals like humans already have less than 1mm contact with all tissue (so that they can get oxygen).

And they can freeze small animals (like hamsters) and unfreeze them and they live...

So what exactly prevents us from hooking the circulatory system to a liquid nitrogen pump and freezing the body that way?

Well, one issue I can think of is that unfreezing would be much more difficult, you'd need some advanced microwave that can focus the waves in a grid of 1mm points too. (The microwave was literally invented to reanimate frozen hamsters but they are small...)

Another issue is that it's just too finicky when freezing because droplets of blood will come into contact with the freezing liquid and freeze immediately and block the blood vessels.

One possible solution I have in mind is that they could use multiple liquids in quick succession like this: quickly and fully flush the blood out with the help of some cold liquid that won't freeze blood and that has a very low freezing point, monitor blood being flushed out, then once done, flush with a freezing liquid with a temperature above the freezing point of the first liquid but below or at your target body freezing temperature.

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