5 Things You Didn't Know About Your Penis

>
Here are some things you might have wondered about your penis, but were
afraid 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 may
remember times when it was completely inappropriate to have an erection; and
yet you couldn't wish it away.

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

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

Just as the penis grows without your consent, sometimes it shrinks. "The
flaccid penis varies in size considerably within a given man," says Drogo
Montague, MD, a urologist at the Cleveland Clinic. Exposure to cold water or
air makes your penis shrink. That's a function of the sympathetic nervous
system.

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

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

(What are the questions
you 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 the
flaccid penis and its full erect length.

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

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

An analysis of more than thousand measurements taken by sex researcher
Alfred Kinsey shows that shorter flaccid penises tend to gain about twice as
much 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 scientifically
established 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 an
erection, 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 big
oak tree above ground, you don't see the root of your penis tucked up inside
your pelvis and attached to your pubic bone.

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

One method of surgical "penis enlargement" is to cut the ligament
that holds the root of the penis up inside the pelvis. This operation may give
some 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 its
upward angle and it wobbles at the base. The lack of sturdiness can lead to
injury.

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 turns
black and blue. And there's terrible pain.

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

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

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

Not all penis curvature is a problem, however. "There is a lot of
variability 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 Nations
Programme on HIV /AIDS (UNAIDS) estimates that worldwide only 30% of
males aged 15 and up are circumcised.

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

The United States has the highest proportion of males circumcised for
non-religious reasons. A whopping 75% of non-Jewish, non-Muslim American men
are circumcised. Compare that to Canada, where only 30% are. In the U.K. it's
20%; in Australia it's merely 6%.

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

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

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