21 things you didn't know about penises

And we don’t mean his watch. A rotten day at work will certainly kill the mood for most guys, but if he just can’t seem to get back in the saddle, a check-up is in order. 'ED can be one of the first signs of heart disease,' says Dr. Joshua Fiske, a urologist at Overlook Hospital in Summit New Jersey, USA 'and other chronic diseases like diabetes and hypertension (high blood pressure) have also been linked to ED.'

Cold weather and cold water are a penis’ mortal enemies. 'Testicles need to be warm to effectively make sperm and testosterone,' explains Dr. Fiske. So after a dip in the pool your guy’s tools will literally huddle up against him to stay toasty - kinda like you do.

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Turns out that human chimney you’re dating may actually be less of a stud than his healthier compatriots. It’s no secret that smoking clogs the arteries, including those that fill the penis with blood at that critical moment. This means smokers may have a harder time rising to the occasion. Bet he quits now!

We’ve suspected this since secondary school and now we have the medical chops to back it up. 'The penis is controlled by the nervous system,' says Dr. Fiske, 'which means erections can occur at random.' Take, for example, that morning wood he’s always so eager to share. It’s most likely the result of impulses firing from the brain during REM sleep. And all this time you thought he was dreaming about the FHM swimsuit issue!

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So forget what you saw in Boogie Nights. 'Adult penises typically measure between three and four inches when flaccid and five to six inches when erect,' says Dr. Fiske. What’s more, when it’s time to get busy, a man who started out on the small side, can end up expanding proportionally more than larger dudes. Just tread carefully when sharing this bit of anatomical trivia - none of the guys we talked to found it reassuring.

Here’s some good news to share with your sweetie: his erect organ is actually pretty large compared to other animals. Chimpanzees, for instance, have equipment that’s about half the size of the human male’s. Of course, our guys do pale in comparison to the blue whale, whose penis is 11 feet long (but who needs that!).

The vast majority of penises lean ever so slightly to the left or right when rigid (you were probably just too distracted to notice). However some bend so dramatically (or curve up or down) that having sex is almost impossible. This is known as Peyronie's Disease and happens when the penis doesn’t expand evenly during a hard-on.

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Unlike those baby blues, penis size, thickness and shape are not genetic. Penises are actually formed in utero when those wild and crazy male hormones kick-in. So if your guy’s unhappy with what he’s got, he has no one to point the finger (or any other appendage) at but Mother Nature.

So don’t take it personally. 'The true purpose of intercourse is procreation,' explains Dr. Fiske, 'and men have evolved to have sex just long enough to get the job done.' In fact 85 per cent of guys can seal the deal in three minutes or less, however it’s the wise man who hangs in there long enough for his partner to catch up - especially if he wants her to make breakfast in the morning.

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OK, no big surprise here, but we did learn that his 'O' actually starts with his spine.  'The signal to ejaculate is the result of muscle contractions in the spinal cord and pelvis,' says Dr. Fiske. Sort of gives new meaning to the insult, ‘you’ve got no backbone.’

Although blokes pride themselves on their ability to go at it like the Energiser Bunny, an erection that simply won’t go away isn’t a miracle, but a medical emergency. 'If the blood flow that causes an erection doesn’t eventually leave the penis,' explains Dr. Fiske, 'serious complications can result, like blood clots.'

Sperm are tenacious little suckers and can hang around, ready, willing and able to cause trouble, for up to two months post-op. So it’s important to use some kind of protection until your man’s doc gives him the all clear. And just in case he’s whining about having this simple little procedure (which, by the way, is far less invasive than a tubal ligation), Dr. Fiske promised us that getting snipped has no effect on a man’s sexual prowess.

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