How come it’s possible to cryopreserve things like sperm and very young embryos, and to later thaw them out so that they can live, but it’s impossible to do that for older humans or anything that consists of more than a few cells?

Question

I mean, sure, there is mummification and and some bodies being naturally preserved due to coldness or dryness, but I’m talking more about the idea of cryonics- the idea that you could stop a biological organism’s entire metabolism in some kind of suspended animation and then later thaw them out and be able to continue living. Most of this is just science fiction though and greatly exaggerated. All of the people who have gotten their bodies cryopreserved as adults are people who have died and it’s essentially just mummification instead of suspended animation.

In: Biology

Answer 1

It’s incredibly difficult to get everything back up and running at the same time. If it’s sperm or embryos that are very small, it’s not that difficult to warm everything up at once.

For an adult human body, that’s much harder; by design, the body insulates its organs, making it hard to warm them up before other things are already warm and need the organs to live. For example, if you were thawing someone out and thawed their skin first before the heart, the skin would start dying because there’s no blood or oxygen being provided by the heart and lungs.