Regarding the previous posts about differences between males and females on holding pee. Those who expressed the opinion that the differences are due to habit not sex are generally wrong. There are real, rather significant differences in the "biological machiney" that men and women use to hold their pee.
I researched this out seveal years ago and I thought I posted it on this fourm once maybe not -- in any case here is my "disscertation" (LOL) on the biological differences between the sexes as regards holding pee.
*****************Biology of Holding Pee by Doc Calloway************
last updated April, 2003
This forum has had numerous discussions about holding urine and many on this forum practice holding their urine. The question of who can hold it the longest men or women as often been discussed. Many people give examples from their own lives but this may or may not reflect the real world of the average person. Since I am a biological scientist (biochemist/ecologist) I spent some time reviewing the urology literature and so here are some medical facts about the “biology of holding urine”.
I know urine holding is a fantasy and is erotic for some people – if you think cold scientific facts will “ruin it for you” then please do not read this post.
First there are two factors that determine how MUCH urine you can hold:
1) Your bladder size and,
2) The power of your tensor muscles in your urethra.
If you are also considering how LONG you can hold it there is another factor:
3) That is how fast your kidneys make urine.
First, on bladder size:
We have heard arguments on this but the facts are that bladder size like all other internal organs (e.g., liver, spleen, kidneys, heart, blood volume etc) can be described by allometry. This means that, on average, there is a constant relationship between your body weight and your bladder size. Big people will tend to have big bladders and small people small bladders. OF COURSE there will be exceptions! (also this would be your “normal” body weight – an overweight person is not a large person in this context).
But a big person with a big bladder does not have any clear “advantage” over a small person with a small bladder. Why? Because a big person will probably also have large kidneys and more blood volume to purify so the big person will make more urine faster than the small person.
So on average men are larger than women so, on average they probably larger bladders so they can probably hold MORE urine – again on average. (obviously there are women in the world who can hold a lot or urine).
Second, what about urethral closing (holding) power?:
Well here males have a huge advantage. It all boils down to three factors these are plumbing, plumbing and plumbing!
The female urethra is about 3 – 4 cm long and the female urethral muscle is about 3 cm in length. In contrast, the male urethra is about 20 – 25 cm long and the male urethral muscle mass controlling his sphincter is over 6 cm long. It is just a much more powerful muscle system in males.
But the male advantage does not end there. The urethral sphincter muscles in females are located only on the sides or the urethra in females. In males the sphincter muscle totally surrounds the urethra and can totally clamp off the tube.
The sphincter on males in much more efficient. Because the treatment of urinary incontinence is a big medical business many tools and instruments have been developed in urology and are use in the science of urodynamics.
Small devices called micropiezometers and these can be inserted into the urethra to measure pressure generated when the patient “clamps down”. On average females can exert a pressure equal to about 60 cm-water – while the average for a male urethra is 85 cm-water. This means with the bladder pressure in the average women reaches 60 cm-water she will lose urine involuntarily while the average man would still be able to “hold it”. Of course there is biological variability but while it is rare for a female to be able to generate pressures as high as 100 cm-water while some males can clamp down with a pressure of 185 cm-water.
In the question an answer session of an incontinence conference a noted European urologist made the comment that a male should be able to contain a full bladder about twice as long as a female due to this fact.
In fact some interesting things have happened as a result of this difference. In the 1980’s when the United States military started letting women into combat positions a strange thing happened. About 15 – 20 % of the women who entered the airborne training experienced involuntary urine loss when they landed from a parachute jump. These women were young (18 – 23 years old), never pregnant and in excellent physical condition. The problem had never been seen in male paratroopers. Likewise 20 - 30% of female college-age atheletes in stress sports like basketball and volley ball have urine leakage problems when under stress. The clamp for holding pee is just not as efficient in females.
The stronger uertheral sphincter is common in other mammalian species also -- e.g., dogs. Nature has not chosen to give males biological advantanges in most areas (age, disease etc.) but this is one are where males are the stronger sex.
In fact, the weakness of the urethra is a major factor behind a large percentage of female incontinence problems. So there you have it this should stimulate some interesting discussion. If anyone is skeptical I can direct you to places where you can read this for yourself.
There is a biological reason for the powerful male urethral sphincter. During sex the male urethra must do double duty – keeping urine out of the semen and keeping semen from back washing into the bladder. Ejaculations are under tremendous pressure so the male urethra needs to be very powerful. In the female the urethra only has one function – holding urine.
So all for a male and female with equal bladder size the man should be able to hold for a larger volume because he can control a higher pressure. However, some of this advantage could be lost if the male produces urine at a faster rate because he would fill faster.
Summary, a male should be able (on average to hold more urine) but how long the urine could be held might be closer and also depend on the rate the two people make urine.
There is a short summary of this information here: http://en.wikipedia.org/wiki/Urethral_sphincter
Cheers Doc Calloway