Urinating from sex organs

July 22, 2006 6:14 PM

Why do humans and animals(?) urinate from their sex organs? Are these two bodily functions in some way related? Are their examples of animals that pee & have sex with parts of their bodies that are spaced far apart?

It seems like a good idea for our eyes to be close to our ears, nose and mouth and all those things to be on our heads: so we can see/smell/hear from greater distances. It doesn't really seem like a great advantage to urinate from where I'm gonna, hopefully later, be having sex though.

I have only a rudimentary knowledge of human biology gleaned from occasional forays into the underwear of the opposite sex, so if I'm using the wrong terminology (organs/genitals etc.) please be generous with your interpretation of my clumsy question.

posted by selton to science & nature (32 comments total)

Incompetent Design
posted by IronLizard at 6:31 PM on July 22, 2006

Just taking a wild guess here... one less opening into the body is one less place for germs to enter?

Women do not urinate from their sex organ (vagina)... they have a separate urethra.
posted by IndigoRain at 6:33 PM on July 22, 2006 [1 favorite has favorites]

And on the flip side, chickens do all three from the same hole. Ergo, chickens < men < women on the evolutionary scale.
posted by hincandenza at 6:35 PM on July 22, 2006

Slight side-note, but worth noting that the Monotremes are the only mammals who have just the "one hole", hence the name.
posted by AmbroseChapel at 6:40 PM on July 22, 2006

This question needs the "cloaca" tag.
posted by Guy Smiley at 6:47 PM on July 22, 2006

I recall reading somewhere that urine will reacidify the urinary tract after the higher ph semen has been ejaculated. Lowering the risk of an infection.
posted by stavrogin at 6:48 PM on July 22, 2006

Like the joke says: Whoever designed the human body must be a civil engineer. What other profession would put a toxic waste pipeline through a recreation area?
posted by pheideaux at 6:53 PM on July 22, 2006 [7 favorites has favorites]

Thanks AmbroseChapel and Guy Smiley: I've added Cloaca and Monotremes as tags.

And many thanks to all the generous answerers so far.
posted by selton at 7:17 PM on July 22, 2006

I've always understood that urinating helps to clean out ones bits, especially for women.
posted by rossination at 7:18 PM on July 22, 2006

Stating the obvious for the good of all: Human women do not urinate from their sex organs- it's actually two separate openings.
posted by ThePinkSuperhero at 7:27 PM on July 22, 2006 [1 favorite has favorites]

Look at it this way. Giving birth is similar to making a big poop.

The bilateral class of animals is ancient (but it includes humans). Members are basically are a long internal tube from mouth to anus. Any differentation from this scheme has to happen at the two ends - because that is where the only gradual change relevant to the outside can happen.

I don't know why bilaterals located sex at the anus. But it seems to be universal. Maybe it was just an accident in the proto-bilateral. Even animals like squids that have special arms (spermataphors) to impregnate their girls have to collect the the sperm from their ass region.
posted by MonkeySaltedNuts at 8:00 PM on July 22, 2006

funny, i've always wondered this myself. I think its in order to force a mental aporia during oral sex.
posted by jak68 at 8:38 PM on July 22, 2006

Well, there are examples of animals that carry their gonads at other locations of their bodies. With earthworms for example the gonads are located at two points along the body.

Also as previously pointed out, women's bodies are not built that way.

For some possible explanations, look at the anatomy of early aquatic chordates. You have your gills up front, which should not be blocked. You have a mouth, which eats everything that fits into it. Both of these together need to be large for maximum efficiency. You don't want to waste energy creating gametes only to eat them, (or have to clear them off your gills) so the gonads go rearward.
posted by KirkJobSluder at 9:12 PM on July 22, 2006

I think the best explanation would be that the animal that would give rise to all other animals had this anotomical design. Thus, this particular trait was inherited by all other animal species that evolved from this animal.
posted by Paul KC at 9:20 PM on July 22, 2006

Hold on, I thought the cloaca was a variant of the tango...

Say, this reminds me of a great quote from Fried Green Tomatoes. Oh, it don't make no kinda sense. Big ol' ox like Grady won't sit next to a colored child, but he eats eggs. Shoot right out a chicken's ass!" (205 K)

I wish guys had a separate pee hole. Because sometimes when you go try to pee after having... you know... the hole is, like, partially glued shut, and pee shoots everywhere, all different directions. I'm just saying, a second tube would be nice.

PS- I'd have put the pee hole on the back of the heel if it had been me designing things.
posted by kookoobirdz at 9:32 PM on July 22, 2006 [1 favorite has favorites]

kookoobirdz writes "PS- I'd have put the pee hole on the back of the heel if it had been me designing things"

I'd hate to pass a kidney stone thru that urethra.
posted by Mitheral at 9:56 PM on July 22, 2006

I can't answer the question, but have a bit of related poetic commentary on the topic:

A woman can be proud and stiff when on love intent; but love has pitched his mansion in the place of excrement; for nothing can be sole or whole that has not been rent.
William Butler Yeats
posted by madamjujujive at 10:16 PM on July 22, 2006

The Pink Superhero - I beat you to that revelation.
posted by IndigoRain at 10:24 PM on July 22, 2006

What is a "mental aporia"? I looked aporia up, but I still don't get it.
posted by joaniemcchicken at 10:27 PM on July 22, 2006

Urinating flushes out bacteria that may have been pushed up inside during intercourse. But why does the urethra need to be so close to the vaginal opening in the first place?
posted by saffron at 3:14 AM on July 23, 2006

While women, unlike men, do have a separate urethra (see labeled photos of a woman's vulva here), the pee still comes out of one place served by one set of pod bay doors, Hal. The original question was fair enough.

As sex bits, those bits are not often used compared to the use they get as piss bits, so the piss bits take priority. Piss goes out the bottom (so as not to get it all over you), and the crotch is the bottom (legs don't count, especially when you're a four-legged beast, as we really are).

Now you have a waste elimination system at the bottom of the body. You could add an entirely new system or double up where possible. (Reusability!) Because these bits rarely are needed for both activities at the same time (though there are a few of you out there), it won't hurt to combine the systems. Fancy parts are biologically expensive.

So that's why your sex bits are at the bottom and (to one extent or another) combined with your piss bits.
posted by pracowity at 3:51 AM on July 23, 2006 [1 favorite has favorites]

Perhaps their similar location is due to both systems, the reproductive and the lower parts of the urinary systems' need to 1.) utilize gravity (i.e.. walking can accelerate labor; gravity helps prevent urine from back-flowing up to the kidney's that filtered it as excretion waste) and 2.) both systems need similar protection that is provided by the pelvic floor muscles (which hold everything up against the gravity) and the hip bones (which support and protect the pelvic muscles and nerves, and help protect all structures from possible external injuries).

Men have a particularly nice design in that their urethra is longer then women's and acidic urine helps flush the tube of some pathogens, helping to prevent kidney infections. And an internal urinary sphincter contracts to prevent sperm from entering the bladder during intercourse. The door to the urinary system is shut when the reproductive system is in action.

Like pracowity said, these systems are doubling up on the (well-protected) real estate.

As for women, the shorter urethra is a shorter route to the bladder for infectious pathogens. And there are 8 external ports of entry to the body cavity unlike men's two, if you include 4 vulvular glands and the cervix at the top of the vagina. Thus women often suffer more from the effects of STD's because there's more places to get in.

Despite the greater risk of infection for women, both systems in women benefit from the protection from the pelvic bones and muscles. A baby in utero is also protected by these structures.

This part of the body is an important one we want to function well in both systems for a long time so we should all, men and women, be doing our Kegal exercises to keep those muscles in shape.

And as for the urethra extending to the heel, while this is very funny, that location would not be protected from external injury (what if that leg was amputated), and circulation problems that develop with age might also help create blockage that would make the heel-urethra stop working. Plus the leg muscles of the heel are nothing compared to the pelvic floor. I imagine the heel-urethra would get pretty leaky. Sorry if I'm blowing that idea. It's still pretty funny.
posted by dog food sugar at 4:50 AM on July 23, 2006

Rephrasing what other people are already saying.... in essence, it may be an accident. Back in the primordial soup, the class of critter that outcompeted everything else well enough to give rise to virtually all animals did it this way. As soon as random variation hits on something that works, that strategy tends to be preserved.

As was also pointed out, since virtually all animals are some variant on the 'long tube' design, the reproduction system would almost have to be somewhere along the tube. Limbs were a relatively late development in evolution, so central functions are not usually located there. (and this is why many creatures can lose one or more limbs and remain functional.) The mention of squid using an arm for reproduction is quite interesting... the hybrid approach between tube and arm is a great example of the weird sorts of things evolution ends up doing.

One big advantage to putting the reproductive organs at one end of the tube is maximum flexibility and reach. This translates to an improved chance of reaching a mate. The mouth is often good at grasping, so putting the organs at the other end gives both an anchor point and a lot of reach. Whether or not this was a determining factor in evolution or just a ride-along with something else... who knows? We weren't exactly there at the time to look. :)

Whenever asking questions like this, remember that we are the sum total of everything that has come before us... a couple of billion years of successful organisms. You share a great deal of genetic material with worms, fish, and even, dare I say, Led Zeppelin.

<hippie>It's all connected, man!</hippie>
posted by Malor at 5:09 AM on July 23, 2006

Great post. I always assumed that, on men at least, it was to "flush out" that canal, but now I'm having second thoughts.

I wish guys had a separate pee hole. Because sometimes when you go try to pee after having... you know... the hole is, like, partially glued shut, and pee shoots everywhere, all different directions. I'm just saying, a second tube would be nice.


Me, Myself, and Irene uses this to idea great effect in one of the best (IMO) comedic scenes in modern cinema.
posted by mkultra at 9:09 AM on July 23, 2006

Which one of your current orifices would you prefer urine to come out of?
posted by blue_beetle at 9:12 AM on July 23, 2006

Which one of your current orifices would you prefer urine to come out of?

My navel doesn't seem to be doing anything important.
posted by horsewithnoname at 2:34 PM on July 23, 2006

I never expected to learn so much, thank you all.


"Which one of your current orifices would you prefer urine to come out of?"

The obvious answer, to me anyway, would be the anus. But that could've been a different question. ie. "why don't we defecate and urinate from the same hole?"
posted by selton at 3:40 PM on July 23, 2006

Could be that males using the same pipe is evolution's way to make sure it's clear when the important business of reproducing comes along. One wouldn't want to have ones guys blocked by the happy place equivelent of belly button lint when the time came.
posted by Mitheral at 4:37 PM on July 23, 2006

The obvious answer, to me anyway, would be the anus. But that could've been a different question. ie. "why don't we defecate and urinate from the same hole?"

The urinary tract abhors bacteria (see: urinary tract infections). The anus is one big bacteria-loving party. The vagina has bacteria, but does not welcome THAT kind of bacteria. It's all rather incompatible.

I second the "Incompetent Design" answer.
posted by heatherann at 6:13 PM on July 23, 2006

a woman can be proud and stiff[...]
Forgive the ignorance, but what was he trying to convey? I read it as an awesome account of needing the buttsex. Or is it supposed to mean something else?
posted by pantsrobot at 10:28 AM on July 24, 2006

pantsrob, there is a copy of the entire poem - Crazy Jane and the Bishop - along with a great discussion of what the poem might mean - it's the last poem on the page. (BTW, this is a pretty good site that discusses many poems and poets.)
posted by madamjujujive at 5:28 PM on July 24, 2006

eh, pardon my typo on your name, pantsrobot!
posted by madamjujujive at 5:29 PM on July 24, 2006