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

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.

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.

2: Your Penis May Be a 'Grower' or a 'Show-er'
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.

3: Your Penis Is Shaped Like a Boomerang
In an MRI picture, the penis looks distinctly boomerang-like.

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 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.

4: You Can Break Your Penis
Here's how to avoid penile fracture: don't use your penis too roughly. It may happen 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.

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%.