5 Things You Didn't Know About Your Penis - CBS News

> Here are some things you might have wondered about your penis, but wereafraid to ask.

No. 1: Your Penis Does Have a Mind of Its Own

You've probably noticed that your penis often does its own thing. You mayremember times when it was completely inappropriate to have an erection; andyet you couldn't wish it away.

It's true that you have less command over your penis than body parts likeyour arms and legs. That's because the penis answers to a part of the nervoussystem that's not always under your conscious control. This is called theautonomic nervous system, which also regulates heart rate and bloodpressure .

Sexual arousal usually isn't voluntary. The conscious mind is complicit init, but a lot of sexual arousal goes on in the sympathetic nervous system. Inaddition, impulses from the brain during the REM phase of sleep causeerections, whether you're dreaming about sex or about a test you forgot tostudy for. Heavy lifting or straining to have a bowel movement can also producean erection.

Just as the penis grows without your consent, sometimes it shrinks. "Theflaccid penis varies in size considerably within a given man," says DrogoMontague, MD, a urologist at the Cleveland Clinic. Exposure to cold water orair makes your penis shrink. That's a function of the sympathetic nervoussystem.

Psychological stress also involves thesympathetic nervous system, and stress has the same effect as a cold shower,Montague says. When you're relaxed and feeling well, your flaccid penis looksbigger than when you're stressed out.

The penis is "kind of a barometer of the sympathetic nervoussystem," Montague says. So the greeting, "How's it hanging?" ismore apt than you might have realized.

(What are the questionsyou have about your penis ? See what other guys have to say on WebMD's Men's Health: Man to Man message board.)

No. 2: Your Penis May Be a 'Grower' or a 'Show-er'

Among men, there is no consistent relationship between the size of theflaccid penis and its full erect length.

In one study of 80 men, researchers found that increases from flaccid toerect lengths ranged widely, from less than a quarter inch to 3.5 incheslonger.

Whatever the clinical significance of these data may be, the locker-roomsignificance is considerable. You can't assume that a dude with a big limppenis gets much bigger with an erection. And the guy whose penis looks tinycould surprise you with a big erection.

An analysis of more than thousand measurements taken by sex researcherAlfred Kinsey shows that shorter flaccid penises tend to gain about twice asmuch length as longer flaccid penises.

A penis that doesn't gain much length with an erection has become known as a"show-er," and a penis that gains a lot is said to be a"grower." These are not medical terms, and there aren't scientificallyestablished thresholds for what's a show-er or a grower.

Kinsey's data suggest that most penises aren't extreme show-ers or growers.About 12% of penises gained one-third or less of their total length with anerection, and about 7% doubled in length when erect.

No. 3: Your Penis Is Shaped Like a Boomerang

Your penis is shaped like a boomerang. Just like you don't see all of a bigoak tree above ground, you don't see the root of your penis tucked up insideyour pelvis and attached to your pubic bone.

In an MRI picture, the penis looks distinctly boomerang-like, as noted by a Frenchresearcher who studied men and women having sex inside an MRI scanner.

One method of surgical "penis enlargement" is to cut the ligamentthat holds the root of the penis up inside the pelvis. This operation may givesome men a little extra length if more of the penis protrudes from the body,but there are side effects. This ligament, called the suspensory ligament,makes an eection sturdy. With that ligament cut, the erect penis loses itsupward angle and it wobbles at the base. The lack of sturdiness can lead toinjury.

No. 4: You Can Break Your Penis

There is no "penis bone," but you can break your penis all the same.It's called penile fracture, and it's not a subtle injury. When it happens,there's "an audible pop or snap," Montague says. Then the penis turnsblack and blue. And there's terrible pain.

Penile fracture is rare, and it typically happens to younger men becausetheir erections tend to be quite rigid.

Here's how to avoid penile fracture: don't use your penis too roughly. Acommon way that penile fracture happens, Montague says, is when a man isthrusting too hard and fast during sex, and slams into his partner's pubicbone. Also, a woman who moves wildly while on top of a man during sex can breaka man's penis.

Peyronie's syndrome is a related condition that tends to show up more inolder men, Montague says. An older man's erection may not be as rigid, butstill is hard enough for sex. Over time, if the penis bends too much a certainway during sex, small tears in the tissue can form scars, and the accumulatedscar tissue gives the penis an abnormally curved shape.

Not all penis curvature is a problem, however. "There is a lot ofvariability in what normal is," Cummings says.

No. 5: Most Penises in the World Are Uncut

A report by the World Health Organization (WHO) and the Joint United NationsProgramme on HIV /AIDS (UNAIDS) estimates that worldwide only 30% ofmales aged 15 and up are circumcised.

Rates vary greatly depending upon religion and nationality. Almost allJewish and Muslim males in the world have circumcised penises, and togetherthey account for about 70% of all circumcised males globally.

The United States has the highest proportion of males circumcised fornon-religious reasons. A whopping 75% of non-Jewish, non-Muslim American menare circumcised. Compare that to Canada, where only 30% are. In the U.K. it's20%; in Australia it's merely 6%.

The practice of circumcising baby boys for medical and cosmetic reasons hasbecome controversial in the U.S. But recently the World Health Organization(WHO) and the UUNAIDS recommended circumcision for adult men, based uponevidence that men with circumcised penises have a lower risk of being infectedwith HIV.

The CDC estimates that about 65% of all newborn boys get circumcised in theU.S.

By Martin Downs Reviewed by Louise Chang©2005-2006 WebMD, Inc. All rights reserved

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