If my liver goes to shit they can swap it out with a new one. If my kidneys break down they can cut me open and drop a new one in. There are heart and bone marrow transplants, skin grafts and blood transfusions.
Well, how far can we take this? Let’s say I have a magic cooler that can provide an endless supply of organs that my body would accept. What kind of organs? Whatever I want. Skin, muscle tissue (are there even surgeries where muscle tissue is transplanted? If not, ignore this one), kidneys, livers, lungs, hearts, eyes, valves, arteries, fingers, toes and hair.
With this magic cooler, 24/7 medical support and today’s technology could I live forever? I’m assuming the one thing that couldn’t be transplanted successfully is the brain- would it deteriorate due to age? How long would it take me to die eventually? What would be the eventual cause of death?
How much functionality do you expect from the new parts? - I expect it’s technically possible to transplant eyes (in the sense of the eyes surviving the process and not just rotting in your head afterwards), but you’re not going to be able to see through them, with anything like our current technology.
Same problem for anything else that needs a lot of nerves wired up - you can get an arm transplant, but its effectiveness will be limited by the extent to which motor nerves can be joined up (individual fingers are a different deal, because most of your hand movements are just puppeted via tendons from muscles in your forearm)
IMO the brain aint going to last all that long. You always hear the 100 year old thats as sharp as a tack, but I’d bet that is the rare exception.
And you can handwave and say “we will fix it” or “we will take stuff to keep it like new”.
Problem is, you might NOT be able to fix it. Or the stuff you’d like to take to keep it like new might keep it from working right.
Yeah, you can postulate supper science and all will be well. But, IMO, in the near future, all these good transplants are going to do is keep you healthy/youngish longer and perhaps buy you some time. Which is great, but far from the live a damn long time scenario people dream of.
Leaving out the obvious chance of multi-organ infection or cancer, your bones will gradually lose their strength. At some point you’ll fall and break a hip. Sure, they can replace the hip, but while you’re bedridden, you’ll come down with pneumonia. Or, your arteries will become encrusted with plaque and you’ll have a heart attack or stroke. Or, you’ll get a deep vein thrombosis, a piece of the clot will break off and lodge in your heart or lungs.
Think of a car. You can replace the tires, the brakes, even the engine and transmission. But once the frame goes, there’s no repair possible.
Also, with a “brain transplant”, it would probably be more correct to think of it as a “body transplant.” The “person” who is aware of the result of the operation is the one who donated the brain.
If this were possible with today’s medical technology, all you’d need is a continuing supply of fresh, young bodies to keep yourself “like new”. You could start cloning replicas of yourself so that, when the time comes, there will be a perfect tissue match waiting for you to inhabit.
Even if you somehow could magically transplant your brain to another body and have all the nerve/blood/etc connections made accurately and fully functional, the brain itself will not live indefinitely. There are plenty of people where the brain is the first thing that gives out.