Are there separate fart and poop muscles?
November 6, 2014 9:24 PM   Subscribe

I have an important human Kinesiology question: are there different muscles for farting and pooping? Specifically, when one has a fart feeling that might be a poop, it feels as though one has the control to selectively let out the potential fart but not the potential poop. Is this a dangerous delusion? Is it really just a "let it all out" switch?
posted by 256 to Health & Fitness (18 answers total) 29 users marked this as a favorite
 
"Sphincters prove effective in the mediation of the entrance or release of liquids and solids; this is evident, for example, in the blowholes of numerous marine mammals."

...and your butt. Further reading: Sphincter ani internus muscle and Sphincter ani externus muscle
posted by jessamyn at 9:27 PM on November 6, 2014 [5 favorites]


I... don't understand the question. Have you never farted without pooping?
posted by jesourie at 9:30 PM on November 6, 2014 [4 favorites]


I mean, usually you can tell the difference. But occasionally you get a feeling that is like both at once. Is it possible to selectively activate your butt to fart if it's a fart but not poop if it's a poop.
posted by 256 at 9:32 PM on November 6, 2014 [5 favorites]


Totally possible. If you're really good you can fart right past a poop.
posted by univac at 9:59 PM on November 6, 2014 [27 favorites]


It may not be a matter of muscle difference, but a matter of a fart and a turd being different. Muscles in your bowel propel both out while the sphincter is the gatekeeper. But a fart is gaseous, so it can slip out easier, whereas a turd is solid and may need more propulsion.
posted by EmpressCallipygos at 10:01 PM on November 6, 2014 [4 favorites]


If you're really good you can fart right past a poop.

If the poops are solid. If they're not solid, you're a lot more likely to shart yourself.
posted by Jacqueline at 10:21 PM on November 6, 2014 [15 favorites]


I'm not a professional buttologist, but I'd imagine solid fecal matter moving further towards its intended destination would push any gas in front of it, building up fart pressure which can feel like fecal urgency, and thus you get a couple of farts before a poop.

See also the cautionary tale of the person who sits, broken-hearted...
posted by Metroid Baby at 11:25 PM on November 6, 2014 [4 favorites]


We're actually looking at basics of physics here: gas, solids, liquid, a valve, a flexible hose, some means of propulsion, and their interaction. I mean. Circumstances vary.
posted by Namlit at 1:39 AM on November 7, 2014 [2 favorites]


Is it possible to selectively activate your butt to fart if it's a fart but not poop if it's a poop.

Yes, because a fart is just compressed gas, so if you just let go the sphincter a little bit without engaging the peristaltic pump, it will blow out on its own like the fizz from the world's least appealing soda bottle.

You do need to have done enough conscious practice with paying attention to what your rectum is telling you to be justifiably confident that any non-gaseous material also in the exit hopper is solid enough not to (be an) issue.

The other end of your digestive tract can do the release-only-the-gas trick more reliably, both because of gravity and because being able to breathe while chewing is pro-survival.
posted by flabdablet at 2:26 AM on November 7, 2014 [14 favorites]


You do need to have done enough conscious practice with paying attention to what your rectum is telling you to be justifiably confident that any non-gaseous material also in the exit hopper is solid enough not to (be an) issue.

A cautionary tale: "At some point in life, everyone has gambled on a fart and lost."
posted by Jacqueline at 5:28 AM on November 7, 2014 [12 favorites]


There's one key aspect of this equation which has thus far been neglected and it's my pleasure to describe to you.

In a normal human GI tract, the sigmoid colon is the "last stop" before waste enters the rectum and subsequently exits your body. If you examine the schematics on that page, you can see that it has a natural "dip" and waste has to sort of get over a bit of a speed bump to enter the rectum from the sigmoid. The physical upshot of this is that intestinal gas may rise, as gas tends to do, over the hump to be expelled through the anus while solid (and even liquid!) waste can stay in the lower part of the sigmoid, behind the speed bump.

Many people lose the ability to pass gas without pooping after surgeries like lower anterior resection that interrupt this natural geography of the GI tract.
posted by telegraph at 5:48 AM on November 7, 2014 [15 favorites]


I'm not a professional buttologist

I heard one on the radio a while back, and she was marveling at the sphincter's design, since it effectively controls the passage of solids, liguids and gases.
posted by Rash at 8:32 AM on November 7, 2014 [3 favorites]


You do need to have done enough conscious practice

You might want to google kegels, kegels exercise, pelvic floor exercise, pubococcygeus muscles, etc.
The aim of Kegel exercises is to improve muscle tone by strengthening the pubococcygeus muscles of the pelvic floor. . . . The many actions performed by Kegel muscles include holding in urine and avoiding defecation. Reproducing this type of muscle action can strengthen the Kegel muscles.
Kegel exercises are said to be good for treating vaginal prolapse, preventing uterine prolapse in women and for treating prostate pain and swelling resulting from benign prostatic hyperplasia (BPH) and prostatitis in men. . . . may be beneficial in treating urinary incontinence in both men and women. . . . may increase sexual gratification. . . . may be of benefit in cases of fecal incontinence and pelvic organ prolapse conditions e.g. rectal prolapse. . . .

 
posted by Herodios at 10:20 AM on November 7, 2014 [1 favorite]


Yes, because a fart is just compressed gas, so if you just let go the sphincter a little bit without engaging the peristaltic pump, it will blow out on its own

Do note that the peristalsis and control of the Sphincter ani internus muscle is entirely involuntary, so this is out of your control. So it comes down to how fine-tuned your valve control is for your external sphincter. That sphincter is the final gatekeeper for both gas and fecal outflow, so as mentioned above the difference between passing a gas and a solid is significant.

Now, if it feels as though you're using different muscles when just farting as opposed to pooping, it's probably because we often employ non-gastrointestinal muscles to help with the poop. You hold your breath, flex abdominal and back muscles, relax pelvic floor muscles, all which helps put pressure downwards.
posted by Kabanos at 10:54 AM on November 7, 2014 [1 favorite]


This may only be tangential to your question, but a worthwhile read nonetheless: The Mysterious Forces of Flatulence:
We will examine the delicate aspects of physics involved, including lift, pressure, velocity, and maybe even branch into complicated stuff like Bernoulli, stagnation effects and nozzle shape. I may even hazard to guess the speed and lift of a typical fart by its acoustic signature.
Includes an important section on "What would it take to fart levitate?"
posted by Kabanos at 11:39 AM on November 7, 2014 [4 favorites]


Well, this is a most dignified discussion!
posted by testmaven68 at 11:06 PM on November 7, 2014 [1 favorite]


"Professional buttologist" gave me the worst case of the giggles.
posted by sarcasticah at 11:49 AM on November 8, 2014 [1 favorite]


Oh man, oh man, oh man. I just took neurobiology and it has never been more relevant. My answer is less about muscles and kinesiology than about sensation which at least in part answers your question about the difference between a poop, a fart and a shart.

Your body has a number of different types of neurons designed to respond to specific stimuli. You have ones that respond to vibration, pain, and heat among other things. What you don't have is a somatosensory neuron that describes wetness, which presumably makes it difficult for your body to diagnose the difference between a fart, some poop and a bunch of diarrhea. However, your body is clever in that it is capable of coupling a few different somatosensory receptors (my professor described it as a cold receptor and a mechanoreceptor) to determine the phase (solid, liquid, gas) of the contents of your rectum. Several times an hour, your internal anal sphincter will loosen just enough such that it can sample the phase of your bowel, generate an appropriate somatosensory stimulus, and thus provide you with the knowledge of whether you want to fart or find a bathroom ASAP.
posted by ghostpony at 6:18 PM on November 13, 2014 [7 favorites]


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