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313983.  Thu Apr 10, 2008 10:23 am Reply with quote

Please can someone help me on this. It's been bugging me for months.

What is the largest internal organ in the human body?

Now EVERYWHERE says it is the liver.

But looking at pictures of the body, I reckon the small intestine is bigger.

Wiki says:

On average, the diameter of the small intestine of an adult human measures approximately 2.5-3 cm


In humans over 5 years old it is approximately 7 m (23 ft) long

My maths says this would give a volume of between 3,500 and 5,000 cm3.

Now, according to this paper (and a load of others online), the liver's volume is in the 1500 cm3 range.

But the problem is that this is a huge difference; so I think perhaps some of my figures are wrong.

Does anyone have any idea? Anything at all?

314017.  Thu Apr 10, 2008 11:09 am Reply with quote

What about the lungs - at about 4 to 6 litres?

314034.  Thu Apr 10, 2008 11:26 am Reply with quote

ARGH! Don't complicate things Will!!!

According to the first site I found, it's claiming around 5000-6000 cm3; but that's for 2 lungs. So I reckon they're still behind my small intestines.

314051.  Thu Apr 10, 2008 11:38 am Reply with quote

Top of head idea which could be utter testicles.

The small intestine is essentially a hollow tube. Does the empty space in the tube count? I know I was once told that the intestinal tract is topologically outside the body, which probably means more to you than it does me.

If I'm right, then the volume of the small intestine would be rather smaller than calculated above. You'd need to know the thickness of the intestinal wall, which is a figure that a bit of Googling has so far failed to reveal.

314059.  Thu Apr 10, 2008 11:45 am Reply with quote

That may be medically correct; but I think to the common-man, "largest" would mean biggest in volume. People would say that a balloon is larger than a golf ball; even though one is hollow, wouldn't they?

314066.  Thu Apr 10, 2008 12:00 pm Reply with quote

Well yes, but then the largest organ of the body is the skin (not the answer to the question because it's not an internal organ).

We wouldn't quote the volume of the skin as being the same as that of the entire body - the figure we would quote would be surface area x thickness (which, incidentally, would typically be in the range 4000 to 6000 cm³). Incidentally, the skin of an adult typically weighs around nine pounds, so a pound of flesh would be about the size of a grapefruit.

So while I take the point that the way you've calculated the volume of the small intestine might coincide with common understanding, I reckon that's not the way it's done by those who cite the liver as the largest innard.

314080.  Thu Apr 10, 2008 12:16 pm Reply with quote

I can't get my new computer to search itself like the old one used to, so I haven't checked this, but I think I recall our mentioning that the skin is the largest organ and then forfeiting Arthur Smith for saying "speak for yourself".

314125.  Thu Apr 10, 2008 2:30 pm Reply with quote

suze wrote:
Top of head idea which could be utter testicles.

Testicles ..... No!

suze wrote:
I know I was once told that the intestinal tract is topologically outside the body, which probably means more to you than it does to me.

That is a fair point and would rule out the lungs too. Not too certain of the finer points of anatomy to know what the human body is actually topologically equivalent too (it would be nice if it was a donut, but I fear there are too many orifices).

314205.  Thu Apr 10, 2008 5:05 pm Reply with quote

Well, have we stumbled on a question here?

Topologically speaking, where are your lungs and guts?

314370.  Fri Apr 11, 2008 5:31 am Reply with quote

Except they're not, really.

It's correct to say that the contents of the lungs and guts are topologically outside your body, but the lungs and guts themselves...? I'm not so sure.

Topologically speaking, the outside of the body can be traced from the skin, through the mouth and intestines, and out the anus (or the other way 'round if you're so inclined). Thus you can say that the "inner" surface of the intestines is topologically external to the body and any food that's "contained" within the intestines is topologically outside the body. Likewise, any air in your lungs is similarly external.

However, to go from that to claim that the intestines and lungs themselves are outside your body would doubtless invite a flood of letters from angry mathematicians.

I also agree with suze about the size of the intestines. Surely the diameter will increase or decrease depending on how much stuff is inside them so, to count that as their total volume is, I think, cheating.

314377.  Fri Apr 11, 2008 5:38 am Reply with quote

I see what you're both saying; but most* medical papers that I have read in the last couple of days, when discussing the size of the lungs/liver/intestines, give the volume in the sense that I gave .

Maybe I could keep everyone happy with the question:

What, by volume, is the largest internal organ in the human body?

Still don't have an authoritative answer tho.


314402.  Fri Apr 11, 2008 5:55 am Reply with quote

Indeed. If you took the intestines out of someone and emptied them, then let them flop on the table, I reckon their volume would be considerably less than the liver.

By contrast, you could probably take out somebody's bladder and inflate it massively. Would that make it that largest organ by volume?

314409.  Fri Apr 11, 2008 6:00 am Reply with quote

dr.bob wrote:
you could probably take out somebody's bladder and inflate it massively. Would that make it that largest organ by volume?

Ooh, I can feel another Boris Johnson joke coming on!

314430.  Fri Apr 11, 2008 6:21 am Reply with quote

Sensing that a person with medical knowledge would be useful for this one, I had a quick chat with Fiona (smiley) about it last evening.

She made the same point as dr.bob about the topological matter - while the empty space inside the organ is topologically outside the body, the organ itself is not. So we can't say that the intestines and lungs are outside the body, but we can say that they are on the outside of the body.

Which causes a bit of an issue with the question as now phrased. We seem to be in general agreement that the skin is the largest organ of all, but it's not an internal organ. Only problem is that on our topological basis, neither is the small intestine or the lung, while the liver is. (Fiona agrees with the suggestion of 1500 cm³ as a typical liver volume, and with 6000 cm³ as typical of two healthy lungs - but that last includes air space, as does egg's value for the small intestine.)

Hmmm, we seem to be able to justify skin, small intestine, and liver as possible answers to the question. Damn. One thing which is undeniable; the liver is the largest gland in the human body. (Rude drinking songs notwithstanding, the male member is not a gland.)

314580.  Fri Apr 11, 2008 11:01 am Reply with quote

What about mammary glands? I'm sure I've seen some that would be larger than the average liver.


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