The Penis: Everything You Need to Know

Zachary Levin

Most men would agree that the penis, though clearly attached, often seems to have a mind of its own. Call it what you like: a unit, trouser worm, or schlong, it's still a strange, disorderly, and frequently disobedient creature. It can be friend or foe, but its inner workings remain a mystery to most of us.

To help us understand the "why" behind some of the most maddening and mystifying tricks the penis can play on its would-be master, we sat down with an expert on the family jewels, Vito Imbasciani, Ph.D., M.D. Imbasciani is a urologist with the Kaiser Permanente Medical Group in Southern California, and he agreed to try to explain some of the penis' most baffling behavior.

Zachary Levin: First of all, what causes "post-pee dribble?"

VI: With a lot of older guys I see, it's because they're peeing through their zipper, and they're obstructing the urethra. If they'd just open their pants and free Willy a little bit, it wouldn't happen. But for most people who consistently dribble after they pee, they're probably over 40, and probably have an enlarged prostate. In a young guy, it's most likely that he's wearing tight jeans, and he's trying to get it out and over his zipper-think of an inverted V. It's just mechanical.

Zachary Levin: Why do men sometimes get hard for no apparent reason?

VI: You can get an erection for any of three main reasons. Sometimes your brain causes it when you see, smell, taste or hear something that turns you on. This centrally originated signal is sent down the spinal cord to the pelvic ganglion, or central relay system, which then sends signals down to the penis.

Then there are the erections you bring on by yourself, by touch. The other unwanted ones are triggered not by the brain, but by the nerves in the penis itself. It could be you're driving along and the motion of the car stimulates the pelvic nerves; you could wake up with a full bladder, and that stimulates the pelvic nerves. A sensory input to the spinal cord sends a signal back to the penis and says to the arteries, "open up!" And you wind up with an unintended erection.

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