A Natural History of the Penis

Ah, the penis, that most essential male organ. No other aspect of the male anatomy demands such attention. Stop for a moment and consider the plethora of names men have conjured for this illustrious male member. It’s kind of like the Eskimo and their hundred words for snow. Priorities, I guess.

As a firefighter, I was surrounded by penises. They were everywhere. At the station, on the trucks, fighting fires… I was completely at ease waking up in a dorm full of woodies.

So let’s take a closer look at this enigmatic appendage.

Sex, of course, is determined before birth by the joining of the sperm and egg and the blending of their associated chromosomes. X plus Y and Poof! - you have a boy. The recipe for a penis is embedded on the Y chromosome, but it takes about eleven weeks of gestation before the genital tuber (from which the penis will sprout) emerges. Ironically, at this stage in development, the genitalia of both sexes look about the same.

But by thirteen weeks, the penis is a penis. This is a lonely stage in its development, for the testes are still tucked away in the abdomen. They’ll descend and join the party by the seventh or eighth month. The descent of the testes leaves behind a weakness in the abdominal wall, thus laying the groundwork for future hernias. So if you’re diagnosed with an inguinal hernia, you have your balls to blame.

We’re all pretty familiar with what the penis does. First off, it’s a conduit for urine (let’s get the dull stuff out of the way). The bladder empties into the urethra before traveling the length of the penis to exit. Since the urethra runs in close proximity to the prostate, many men suffer from incontinence when the prostate is damaged or removed.

But urine is not the only fluid carried via the urethra. Let’s talk semen.

The male reproductive system, at its most basic, is composed of the penis and testicles, but includes all the organs, ducts, and vessels that allow it to do what it does. Let’s start with the testicles and work our way forward.

The scrotum is a fleshy sac that holds the testes. It is composed of skin and muscles and forms two side-by-side pouches: one testis per pouch. It’s the smooth muscles of the scrotum that allow it to magically rise and fall. Body too hot? Scrotum drops. Body too cold? Scrotum draws up. Temperature extremes wreak havoc on sperm production. It’s the scrotum’s job to keep things comfy.

The testes (testicles) are responsible for sperm production. They also produce testosterone, which is why boys destined for the opera in 18^th century Italy were castrated. That way, they could continue singing in those beautiful falsetto voices.

Sperm produced in the testes then move into the epididymis – a network of thin tubules, several feet in length, that are bundled on the top of each testicle. This is where the sperm mature before being transferred up into the abdomen to the seminal vesicles – a pair of lumpy glands located on the backside of the bladder. The vesicles produce some of the liquid portion of the semen, which contains proteins and mucus, and has an alkaline pH. This enables the sperm to survive that oh-so-acidic environment of the vagina. And here’s an interesting tidbit: the liquid also contains fructose, which provides a snack for the sperm should there be a lag time while awaiting an egg.

The ductus deferens carries the semen from the vesicles and joins the urethra at the ejaculatory duct (things are getting interesting). It’s this amazing little duct that propels the sperm up and out during ejaculation. In fact, it’s so effective that it can propel semen up to two feet away (please don’t try this at home)!

Enabling all the magic is the penis itself. This mesmerizing cylinder of flesh contains large pockets of erectile tissue which, when aroused, fill with blood, making it stand at attention. The erectile tissue also increases the size of the penis (goody!) and assists with insertion. Once inside, movement and friction along the shaft provide just enough gumption for the ejaculatory duct to do its thing and voilà! Ejaculation!

Recent research has shown that boys, like girls, are reaching sexual maturity earlier; by approximately two and a half months per decade since the 1800s. Scientists attribute it to better health and nutrition. As boys hit puberty, though, their chance of death increases, mainly due to higher levels of risky behavior. When testosterone production peaks, apparently you guys go bonkers and your tendencies for "dangerous and reckless shows of strength, negligence, and a high propensity to violence" increase your chances for fatal accidents; what researchers call the “accident hump” (let the snickering commence). So for you youngsters out there... should you have the urge to jump off a building, try masturbating instead.

Lastly, we must address the issue of size. And how do our males fare when compared to our closest primate relatives? Quite well, actually. Compared to chimps, humans are much more endowed. Even gorillas can’t measure up, although I’d pay good money to see a side-by-side comparison. And while we’re talking size, let me clarify a misconception. Bigger is NOT always better. The female body can only accommodate so much girth before pleasure morphs into pain, so quit your bragging.

I’ll close with a fascinating bit of information from evolutionary biologist, Jerry Coyne. His website provides a world map of penis sizes, compiled by Dr. Eduardo Gomez de Diego. Keep in mind, lengths are based on self-reporting (and we know how you boys exaggerate!) and the sizes are in centimeters (didn’t want the Americans to fall out of their chairs). So take a look and see how you fare. Without going into detail, I’ll simply say for my readers in Thailand and India: don’t sweat it. As for my readers in the Congo – give me a call!

I'll leave you with a video tour of your junk. Have a great week and don't forget to share the blog!