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This might sound like a silly question at first, but think about it; Marine ribcages are fused together, right? One solid lump of bone, basically. I'm sure that makes them harder to stab to death, but it can't be easy for them to move their torso around with zero spinal flexibility above the stomach and below the neck. And if they suffer injury or disease to their diaphragm, exactly how do they get air into their three lungs, eh? You try moving around and doing everyday tasks whilst keeping your ribcage completely tense and see how far you get.

Yay, a question I can answer knowledgeably! I spent a stint in a medical unit in the army(I shoot big guns but medics need protection too) and picked up a bit of butchery/battlefield surgery.

The ribcage does flex a bit, but has nothing to do with movement. The flexibility we gain from the handful of vertebrae the ribs attach to is negligible, so we don't even worry about it when bracing people for transit. Breathing SHOULD move the lower gut primarily because of where the most oxygen grabby parts of the lung are(read: the bottom of the lung).

Power armor doesn't flex anywhere but at joints, so them trying to arch their back would yield no results anyway. The rest of it has to be chalked up to fluff and 'it just works'. I poked around the SM codex a bit and found what they say not implausible but not happening in my lifetime.

Again, I gotta stress that I am a trigger jockey, not a doctor or nurse. I put holes into people more than I fix them up, so take the above with a grain of salt.

-cgmckenzie

cgmckenzie wrote:
Again, I gotta stress that I am a trigger jockey, not a doctor or nurse. I put holes into people more than I fix them up, so take the above with a grain of salt.

-cgmckenzie

ill take your field experience over a dry medical report any day of the week

I'm just a pre-Med student, so not a final authority or anything but I do know human anatomy/physiology fairly well.

As already mentioned, yes there would be reduced mobility involved with having a fused ribcage. The structure of power armor would restrict movement even more though, so the ribcage structure handicap wouldn't be noticable comparatively.

The real problem would arise from the fact the Marines wouldn't have useable intercostal muscles. During high intensity physical activity the human lung tidal volume (amount you breathe in and out) increases, meaning with each breath you inhale and exhale more air. The increase in inhalation is caused by the external intercostal muscles (muscles on outside of the ribcage) flexing, and increased exhalation is caused by the internal intercostal muscles (muscles on inside of the ribcage). These muscles change the volume of the chest cavity, thus altering the pressure in the lungs relative to the external atmosphere. Abdominal muscles also help with exhalation. If you had a solid ribcage you would only be breathing with your diaphragm, and during exercise you'd have a hell of a time increasing the amount of oxygen you recieve. IMO that is the huge handicap. Solid ribcage= less oxygen=less energy=less effective in combat/exercise. Realistically, someone with the anatomy of a Space Marine would have less endurance than a guardsman (aka an in-shape human) would.

Sorry Marine fanboyz, their anatomy is highly flawed. There are others, but this is one of the bigger ones. Good thing its just a game.

The biggest problem with having a fused rib-cage medically is the inability to fully inhale. What allows humans to inhale to the fullest is the flexibility of the ribs which is from them NOT being fused together. But with all the other incredible things done to marine's physiology one can just say "Its the 41st millennium. They can do that."

Pre-RN here btw.

-Cypher- wrote:The biggest problem with having a fused rib-cage medically is the inability to fully inhale. What allows humans to inhale to the fullest is the flexibility of the ribs which is from them NOT being fused together. But with all the other incredible things done to marine's physiology one can just say "Its the 41st millennium. They can do that."

Pre-RN here btw.

The third lung probably also helps in that particular department.

So a marine is more likely to have ribs that have enlarged but rather than fusing overlap each other to retain movement. I had a quick look on the net and insects which are surrounded by a hard shell don't even have lungs.
An interesting observation here, thanks for the thread.

Having an extra lung doesn't make it any easier to draw air into your lungs without any rib movement. Try holding your chest and seeing how much you can breathe in - and out - whilst keeping your ribs still. Now try meeting the oxygen needs of a body that's likely got several times your muscle mass for several hours of constant fighting with that kind of air intake...

It's important to remember that SM are not humans, not anymore at least. Major differences that affect this particular problem(in no particular order):

1)Different metabolism means different needs/rate for oxygen consumption. It is possible they can get what they need from a whole slew of different gases.

2)Improved muscle strength all around would lend some to the diaphragm.

3)3rd lung will absorb more oxygen/what ever gas they can breathe.

There are more that will affect this, but not as directly and I don't remember the rest w/o pulling out my codex.

Tech wise, they could be breathing a specialized gas through in-helmet that has more of what they can process.

Most of the air drawn into our lungs is 'dead space', meaning it isn't used. Their lung system probably has a way to use as much as possible of that area.

-cgmckenzie

In regards lung intake and rib expansion, you're all assuming that the lungs are right behind the ribcage in a marine like they are with us. It may be that the ribcage expands to a greater extent than the lungs do leaving more of a gap between them. This would allow the lungs to operate at full capacity without being pushed up against the ribs.

cadbren wrote:In regards lung intake and rib expansion, you're all assuming that the lungs are right behind the ribcage in a marine like they are with us. It may be that the ribcage expands to a greater extent than the lungs do leaving more of a gap between them. This would allow the lungs to operate at full capacity without being pushed up against the ribs.

So there would be a cavity between the lungs and ribcage, allowing them to expand?

According to lexicanum, Space Marine bone ossification doesn't form a solid, turtle-like shell out of the ribs, but forms "interlocking plates," like cadbren had brought up.

Jordan wrote:According to lexicanum, Space Marine bone ossification doesn't form a solid, turtle-like shell out of the ribs, but forms "interlocking plates," like cadbren had brought up.

+1

IMO, SM are still able to breathe normally (as well as turning around, I have some doubts with bending over though) because their ribcage is not completely fused.

Just imagine the ribs of a normal human:

but being extended, larger if you wish, forming some kind of bone strip around the lungs, where each rib is overlapping on the rib immediately below it. A bit similar to the chest armor of roman legionaries:

Lexicanum wrote:Ossmodula
Phase 2: A small, tubular and complex organ, the ossmodula secretes hormones that both affect the ossification of the skeleton and encourage the forming bone growths to absorb ceramic-based chemicals that are laced into the Marine's diet.1 This heavily alters the way the Space Marine's bones grow and develop. Two years after this implant is first put in the subject's long bones will have increased in size (along with most other bones) and the rib cage will have been fused into a solid mass of bulletproof, interlocking plates.

This is what prompted me to start the thread. I interpreted this (and the - now retconned as a mad biologist's heresy - fluff about 3E Tyrant Guard having solid fused ribs being from absorbing Marine DNA) to mean 'turtleshell'. The 'overlapping extended ribs' interpretation makes a lot more sense to my A-level Biology; is there any official fluff that contradicts the 'turtleshell' interpretation of 'fused' ribcages and lays the matter to rest?

Why would a SM bend over if he could just kneel. Nothing looks stupid when a Space Marine is doing it.

Frolicking through a garden might look stupid in power armor...

-cgmckenzie

Not if it's the Garden of Nurgle.

htj wrote:

cadbren wrote:In regards lung intake and rib expansion, you're all assuming that the lungs are right behind the ribcage in a marine like they are with us. It may be that the ribcage expands to a greater extent than the lungs do leaving more of a gap between them. This would allow the lungs to operate at full capacity without being pushed up against the ribs.

So there would be a cavity between the lungs and ribcage, allowing them to expand?

Maybe not a cavity, but a plastic substance that functions like packing foam so the lungs aren't banging around on their own but are able to expand "normally" into this substance while the hard outer shell of the ribcage protects the whole lot.

They would look stupid trying to shuffle...

lindsay40k wrote:

Lexicanum wrote:Ossmodula
Phase 2: A small, tubular and complex organ, the ossmodula secretes hormones that both affect the ossification of the skeleton and encourage the forming bone growths to absorb ceramic-based chemicals that are laced into the Marine's diet.1 This heavily alters the way the Space Marine's bones grow and develop. Two years after this implant is first put in the subject's long bones will have increased in size (along with most other bones) and the rib cage will have been fused into a solid mass of bulletproof, interlocking plates.

This is what prompted me to start the thread. I interpreted this (and the - now retconned as a mad biologist's heresy - fluff about 3E Tyrant Guard having solid fused ribs being from absorbing Marine DNA) to mean 'turtleshell'. The 'overlapping extended ribs' interpretation makes a lot more sense to my A-level Biology; is there any official fluff that contradicts the 'turtleshell' interpretation of 'fused' ribcages and lays the matter to rest?

It is possible for a biological joint that is fused to be flexible? Plants have spongy cells that allow wood and leaves to bend, perhaps the fused surfaces are some type of spongy bone, perhaps filled with fluid, that allows more flexing than normal bone does. Heck, with the way a marine's body can repair itself, maybe these fused joins are constantly tearing and being repaired, several different possibilities here.

[heresy]SM's as portrayed look stupid without having to do anything [/heresy]

There is a lot about SMs imho that make them look daft and the ribcage is but one.

A friend of mine has a condition in which the bones fuse together. Her father has this and his rib cage is fused so breathing and movement is difficult.

Not recommended for a fighting demi god

The there must be more space in the chest cavity, so lung capacity is most likely increased.

Playing with kittens would also make them look stupid.

-cgmckenzie

I would also like to point out that they have better blood then the standard humie as well. Their blood is MUCH more efficient so they actually don't need to draw as much breathe as we do either.

They're ribcage is not one solid mass. it is composed of overlapping plates which are free to move over each other, whilst still plugging any gaps that those nasty bullets and knives would otherwise squeeze through. So they can draw as much breath, it would just require more effort. Hope that resolves some stuff.

A wizard did it. Anyway, I think the example of Legionnaire armor above is the only plausible explanation. The ribcage presents a solid front of bone for any attacks, but still has the flexibility to permit breathing. Add a fancy third lung that can probably inflate/deflate itself, and there you go. Space Marines are incredibly wide, so having chest-cavity real-estate is not really a concern.

I'll echo what several people above me said;

One - the ribcage is made of overlapping plates, allowing some degree of flexibility.

Two - much more efficient oxygen transport (more/large red blood cells).

Three - they're so much BIGGER than a human. Even saying the lungs were slightly impeded (which I doubt, in the Emperor's wisdom, he would allow) the size of the lungs negates this.

Four - the human body only takes on a portion (1/4-1/3) of the oxygen we breathe in with each breath. I'm assuming Astartes lungs would be far more efficient at this than ours.

Not being contrarian here, but many of these points don't ring true with me.

The 'better blood' point is perfectly fine, as is the 'power armour feeds them better air' one.

The 'greater lung capacity/extra lung' point doesn't help, because a Marine has a LOT more muscle mass to oxygenate than a normal human. Whether the increased oxygen demand is matched or exceeded by the increased lung capacity is unclear.

The 'better quality lungs' suggestion feels off to me. The structure of a lung is pretty much determined by the individual's genes. You can induce growth with hormones, you can Igor in extra organs, but this is a structural rather than a measurement change.

The 'third lung can inflate/deflate itself' postulation is very unlikely. That would require building a lot of biological supporting structures that aren't hinted at in the fluff (to my knowledge) and would be extremely difficult to piggy-back onto a human nervous system. (Not discounting this, as 40K science has wings being grafted onto humanoids.)

The 'flexible overlapping plates' interpretation seems to me to ignore the word 'fused'. If bones are fused, they don't slide over one another. That's the point of fusing bones together. If GW were to Squat the fused ribcage in favour of an overlapping ribcage, that's all well and good. But to my knowledge, they haven't.

If the ribcage was fused into 3 overlapping segments it would make sense in their use of the word.

cgmckenzie wrote:Frolicking through a garden might look stupid in power armor...

-cgmckenzie

You mean like this?

http://www.dakkadakka.com/gallery/15029-.html

That doesn't look stupid at all. It needs to be in a GARDEN. Jeez, its not a hard concept.

-cgmckenzie