What is between the internal organs?

We put this to Naked Scientist Chris Smith...

Chris - Right. We've got this question from Luke:

What is in between the internal parts of the body. I'm assuming it can't be air or blood which would get stale and prone to infection due to lack of circulation. It's not going to be a vacuum, and I doubt that the organs are all jammed in with absolutely zero space. So what is in there? Chris - What do you reckon Georgia - what's in there?

Georgia - in between? Jelly.

Laughter

Chris - In my case I think it's expanding amounts of flab. But the answer is, we know the answer to this rather well because we've actually got very good imaging modalities now. We've got CT scans, we have MRI scans, we have X rays and so we can see what's inside a body when it's in its intact state.

And the answer is that, actually, there is no free gas inside your body unless you have a problem. If you do a chest x ray on somebody you can see where the gas is in their lungs and you can also see that the lungs go right out to the chest wall and there's no gas outside the lungs. Now sometimes people get a condition called a pneumothorax, and this is where the lung pops and you get air outside the lung, and doctors looking at an X ray of the chest would see that there's a bubble of gas around the lungs and you can see that it's clearly where it shouldn't be.

The same is true in the abdomen. The innards, if you actually look inside the abdomen actually most of the stuff in their, your guts and all the internal organs, they're all slippery and slimy and covered in water. But they're very closely packed in and sliding past each other and there is no free gas in there.

If you do a chest X ray on somebody, you do this to diagnose abdominal problems because you do a chest X ray with someone upright and you can see where their diaphragm is and you can see a bubble of gas forming under the diaphragm. And that's always pathological and shows they've had some kind of rupture of one of their internal organs, or that a nice surgeon has been in there and done something recently and left some gas in there. Because when we do laparoscopic surgery, when they put a camera in, actually what you do is to put a needle in and you blow up the person's abdomen with carbon dioxide and inflate their tummy, so that it lifts the abdominal wall away from the internal organs and that way, when you put your instruments in to start with you don't do damage and you also create space for yourself in which to work. And you use carbon dioxide because it's easy for that to be reabsorbed into the body. It dissolves back in your body fluids and then it disappears off through your lungs. Peter.

Peter - Isn't there something called peritonitis? Isn't that something where there's an infection within the abdomen - what is that?

Chris - Well, peritonitis is where you have infected the layers around your peritoneum. Your peritoneal cavity is your abdominal cavity, and if things get out of your intestines and into that space, they set up peritonitis inflammation there. You can also get chemical inflammation of the peritoneal space but, on the whole, that's always pathological, and it can also be because of say, cancer. That can do that too. Doug?

Doug - Just quickly because we have two physicists in the room here. I think we would point out that the vast majority of the things in our body are, in fact, empty space between the nucleus and the electrons. So, we are mostly not there at all.

Chris - I thought you were going to say like in some people's heads there's quite a gap as well. Your non-adopted county's newly elected president has something going on in that department, doesn't it.

Doug - I can see a theme developing here! So the audience knows I am British now, okay.

Chris - To summarise the question: what's inside a body. Well the answer is that there is no free space, there is no wasted space, and it's largely fluid and things all in a position with each other. But where you do end up with a whole or something that's no there you do sometimes get a bubble of gas and doctors can spot that, and they know when they see that that there is something going wrong.