Why isn’t any air expelled when we urinate (through the urethra, not the anus, I realise it’s common to fart when you pee). You would think that some air would get trapped in the bladder and need to be either absorbed or passed.
What does happen to any air in the bladder since, as far as I can tell, I have never released any externally.
Remember, this is the Straight Dope, so no making jokes about farting penises.
How would air get in the bladder?
There is (usually) no connection between the urinary tract and anywhere that air or gas is produced. So, it’s not too surprising that we don’t fart through our urethrae (pee tubes).
Now, if you were talking about those unfortunate souls with fistulae (abnormal connections) between their bowels and urinary tracts, I could blow you away with information.
There is no way for air to get in there. The urine is extracted from your blood, and if you have air in your blood you will have more things to worry about than farting when you pee!
Farts are created by bacteria in the intestines digesting fecal material and producing methane gas. There is no such potential nutrient source for bacteria in the bladder. Since no gasses are produced in the bladder, and there is no other anatomical mechanism for air to be introduced into the bladder, there are no gasses in the bladder to be expelled during urination.
What is left in the bladder after a pee then? Nothing? Wouldn’t that make it a vacuum? If air cannot get into the bladder, how do we pee at all?
Nothing. The bladder is an elastic bag, not a solid, rigid tank. It collapses (flattens) and shrinks as it’s emptied, just like a tube of toothpaste or a rubber balloon.
It’s a bladder, not a beaker. It’s very good at stretching. Bladder tension coupled with certain muscle contractions causes the urine to be expelled.
See, that’s what I was wondering. According to the replys so far there is no function that would produce air (or any gas) in the bladder.
What about certain folks with a bladder infection? Do the bacteria in this case produce a noticeable amount of gas?
Also, is there any (im)balance of chemicals/nutrients/waste that collect in the bladder that could cause gas to develope?
As I said above - people with connections (fistulae) between their urinary tracts and their intestines will have pneumaturia (farts in their urine).
Another, rarer, possibility is so-called emphysematous pyelonephritis (almost always occurring in diabetics) where there is a huge amount of infection in the kidney, and, due to the presence of high sugar levels, the infecting bacteria produces a lot of gas due to its fermentation of the sugar.
No, the bacteria from a UIT won’t make a noticible anoumt of gas. For one thing, there is a LOT of bacteria in the intestine and a LOT of food there for them to eat and make gas with. For most people, there isn’t much food in the urethra or urine, so there isn’t as much bacteria, even with a UTI. Plus, they are certainly different types of bacterai with different wastes.
Gas is sometimes used during radiographic studies as a contrast agent. When gas is introduced into a dog’s bladder for a pneumocystogram, one of the humorous aspects are the mini-farts when the dog passes air via its urethra. (It is funny hehe, not funny HAHA).
Ah, now we’re on to something. Where does this gas go? In what fashion does it escape?
Obviously, it makes a pssssssssss sound.
Sorry.
Nitpick: Aren’t farts mostly carbon dioxide? Methane is awfully high energy to be expelling as a waste product.
I’m pretty sure that cows produce LARGE quantities of Methane, so much that it has occured to people to try and reclaim some of it. How, I have no idea.
Farts are mostly carbon dioxide, methane, and hydrogen along with a submixture of odoriferous compounds. They’re all gases produced by bacterial fermentation. Different species of bacteria working on different foods produce different mixtures of gases. Not everyone has methane-producing bacteria and only the breakdown of lactose produces hydrogen. It’s hard, therefore, to generalize about composition.
KarlGauss I, for one, am interested in these urinary fistulae. Please continue. Any sort of horrible personal anecdotes would be appreciated.
I don’t think they reclaim it directly from cow farts, but here’s a site on “biogas”.
Physiology 101.
Carbon dioxide is the product of oxidation or combustion. Also by photosynthesis.
Bacterial decomposition produces methane. Hence nasty smelling gaseous products…