In reference to crocodile icefishes: "Their blood is transparent because they have no hemoglobin and/or only defunct erythrocytes"
[url]http://en.wikipedia.org/wiki/Crocodile_icefish/url]

Yeah, I guess you're right, just found this awesome thing on wikipedia!

The only thing I'm wondering though is, why do humans and most vertebrates have a complex respiratory system if they could instead just absorb oxygen through their skin like this animal?
I guess if the brain were put in a vat of highly oxygenated water that would allow it to absorb oxygen without drying out, though i'm not sure if cells in the human body are really designed to receive oxygen without the aid of red blood cells.

Dude, what?
Lets have more science less Yoga theory.
Brains need oxygen, carried in some sort of blood (see Duh's post on substitutes). That is all.
Although, you'd want to give the brain some sort of input/output, or it will go insane VERY QUICKLY.
I suggest something to do with the optical nerve, so one can watch TV while they set everything else up

Because in an evolutionary context, there was never any specific pressure to form this system for the vertebrates.

Likely having a dedicated respiratory system is more efficient. As a rule of thumb, a biological system is generally more efficient if it's main task is it's only task. So say the gastrointestinal system, who's main purpose is to break down food into base components for easier absorption. It is much more efficient than an amoeba's, who's entire body functions as GI system, skin, heart, nervous system, etc.

From that wiki page...
"This works because water can dissolve the most oxygen when it is coldest."
This means we (or our disembodied brain) must be dipped in arctic-ice-cold water to be able to absorb dem oxygen. Human brains can't think that good when they're freezing, though.
Also, some frogs absorb oxygen through their moist skin... but this has another water problem. They get dehydrated, they suffocate. Thus a complex respiratory system enable us to spread to all corners of the globe. They absorb oxygen without dehydrating us in the process... or at least, not as fast as skinbreathers.

according to DR the brain present in the game is not necessarily human.
that being said if we absorbed oxygen from our skin it would imply a very complicated circulatory system at the epidermis (skin).
this would cause many problems (in order of least to most serious):
1. the skin is not close to the heart (compared to the lungs)
2.your skin would have to be especially thin to allow oxygen to diffuse through
3.if you got cut you would piss blood out your wound from the milions of capillaries that were sliced open

Adressing the blood problem:
it might be possible to keep some bone marrow alive inside to produce red blood cells for the brain.

Yeah, thats what I said a few posts ago about the hemopoetic tissues, ie. bone marrow. You would also need a spleen and liver attached as they are also involved in the blood cell making process.

Doing this would probably be the best way to supply oxygen to the brain, because, as carriontrooper said, the brain wouldn't fare too well in freezing water. The reason why oxygenated fluid wouldn't work as well as red blood cells would be because oxygenated fluid can't selectively decide which cells to supply oxygen to, instead, it would oxidize the first veins it flowed through alot, which you wouldn't want, and not supply enough oxygen to the parts of the brain further down the veins. Red blood cells, on the other hand, only give oxygen to cells which are depleted of oxygen, instead of just oxidizing everything around them like an oxygen-rich fluid would do. Another important role which red blood cells play is removing carbon-dioxide from cells depleted of oxygen. Oxygen-enriched fluid couldn't do this.

alright, so, i think this is it. correct me if i'm wrong. we need artificial carriers for the red blood cells. they need to carry oxygen. their issue? they die too quickly. solution? extended lifetime of the cells and a bone marrow source that would constantly clone itself(for when it gets too old to be efficient[kept in cold storage until used]) to make up for the dead. and then the blood also needs to be cleaned, so i guess we would also need a dialysis machine?

Heh, this gets more and more complex, eventually were going to need a whole human body to operate this brain!

I don't understand what you mean by "we need artificial carriers" for the red blood cells though. If you had a biological system of generating, that would be self sustaining and wouldn't need artificial carriers.

I'm pretty sure red blood cells don't select either. It goes down to a matter of diffusion. When oxygenated blood passes by cells, it releases oxygen and absorbs carbon dioxide because there is a higher concentration of oxygen in it than in the surrounding fluid (the cells take in oxygen through active processes to the best of my knowledge) and the opposite is true with carbon monoxide. So, any fluid that is capable of carrying both carbon monoxide and oxygen can substitute for red blood cells, though it will not have as many useful functions such as vessel dilation and clotting properties.

i meant artificial because of the improvements to the blood cells. now, about preventing brain atrophy...

What the ♥♥♥♥ is this ♥♥♥♥? This thread is hard to read without hemorrhaging my sanity from every orifice.
We can already replace the heart, lungs, liver, pancreas, ♥♥♥♥, we can replace a lot of the torso. Also ears, (badly) eyes, and soon tongues. Fleshy bodies are fine, and if you know any biology, more effective for the (kilo) calorie than comparable mechanical prosthetics. However, the big advantage to a prosthetic is the inherent modularization of the human form. That is to say, once you fix a heart once, you can usually fix that new heart in a more routine way. Machines are more easy to predict inversely proportionate to their complexity, and a human heart is vastly more complicated than a peristaltic pump.

Glovedude, I think you are getting terminal shock confused here, as you do not need an organic heart to survive. There is a nerve response to your heart stopping, but it's not fatal (though usually really sucky, thus heat attack victims passing out). My grandfather's getting pretty close to triple digits, and has heart, ear, and eye issues. He's had a titanium plate installed on his skull, and an internal hearing aid. It's pretty freaking awesome; he can now plug his DS right into his head. His increasingly painful heart attacks are not.


I'm taking a med class in college now, just because I felt like it, and it was practically free.
We spent three days discussing this out of our textbooks, after a small group made it into a big debate.
In the end we concluded that humans will probably retreat from our physical bodies only if we've totally screwed over the world outside, as there are too many things that the flesh allows for that would be hard to emulate initially. Obviously, that will change for the better.

Damn, writing this sapped time I'll never see again.

Edit:
Now, to go the other direction, why not focus on first understanding how our flesh works more completely, and then producing cloned flesh replacements? With a little genetic tweaking, we can all be blood type O, perfectly moddable, and have powerful symbiotic bacteria for making the most out of our digestive tract. Imagine, a cut sealing itself because your red blood cells have the new feature of extending flagella and tying together, rather than coagulating slowly. You might be able to sustain more grievous wounds without dying of blood loss.
Or harness the awesomeness that is the virus particle! Genomic patches may be distributed in viral form, ready for injection and assimilation. For instance, vaccination by injecting T Cells with a modification for the immune system, to better fight a newly discovered disease.

Now he is talking.

Rather than removing the fiddly organics we don't understand and replacing them with more simple machines, we embrace the efficiency of biotechnologies (no, not yoghurt) and make ourselves indestructible and immortal THAT way.

It is possible, just a lot trickier.

Oh, I don't know about more efficient, but probably cheaper to grow in a lab out of gravy, and then recycle biomass with more biomass.
There will, however, be huge losses in energy transfer.

Also more flammable.

I respect your position, and it makes sense, but I still want my robotic body with nipple lasers.