November 17, 2010

The Different Kinds of Sperm

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So everyone knows what semen is for, right? Right, being the main subject of the final scene in a porno. Did you ever stop to think what’s really going on in our semen? Probably not, but I promised to write the article, so here’s the skinny on the spooge.

So everyone knows the story of the birds and the bees: your wingmen bees filter off the lady bee’s friends; you fill the lady bee with booze; and then you spend the next 10 minutes explaining to her that this never happened to you before (or is it just me?). Well, if you’re not me, you probably slept with her and sent forth your sperm soldiers.

Soldiers is a really appropriate nickname for sperm. Most people don’t know there are many different kinds of sperm that all work together to make sure you’re the father of that little kid no matter what you claim on the next Jerry Springer show. So far, we’ve identified four different kinds of sperm:


These are fast swimmers who hunt for the egg to deposit your mini-me into the egg. This is the kind that everyone thinks make up all the sperm in semen. The truth is that these only make up about 10 to 20 percent of sperm. The rest are a mix of the following types.


These are slow swimmers. They usually linger around the cervix like underage kids trying to get into a strip club (shout out for the hard-working ladies in the clubs). These sperm link tails together like they’re re-enacting the Hands Across America video. When they link up, they form a wall to block out other people’s sperm. It’s nature’s sponge.

Search-and-destroy sperm

These are killers. They have no DNA, so they wouldn’t know what to do with an egg even if you put them next to one and got both liquored up real good. Instead, they have an extra dose of enzymes that pop other sperm (called lysing enzymes). They recognize foreign sperm and kill them. And you thought we men were jealous.

Family-planning sperm

These sperm are indiscriminate killers. They linger behind and kill every sperm in sight, even your own. We’re not exactly sure why they do this. Could be partly to keep others from getting you pregnant, could be a way to kill off slower, defective sperm. Shrug.

Superglue Goo

There’s a common myth that washing semen with water turns the proteins into scrambled eggs, and that’s why it turns to rubber cement (sement?). This isn’t the case. Guys make a natural superglue in our semen (and you thought we weren’t handy). This gelling protein has two jobs.

First, it makes sure sperm get stuck inside our lady instead of running out. The warmer temperatures inside the woman cause the protein to join up into a mucus plug. This isn’t at all what happens when you cook an egg. That makes the protein lose their shape and clump together. The mucus plug is much more efficient.

The second job of the gelling protein is defensive. It makes a gel to keep others from coming in after you and getting your lady pregnant.

Feel-Good Drugs

Some women say they’re in love with semen. Science to the rescue! We have evidence that backs up the thought they are on to something. A university study looked at 293 female students, and divided them into groups depending on how often their partners wore condoms, and assessed their happiness using the Beck (not the soccer player) Depression Inventory.

The team found that women whose partners never used condoms scored better when compared to women who sometimes used condoms. Women who always used condoms scored the worst. They looked for women who weren’t having sex, but this is college, that’s an impossibility! I guessed they looked harder, because they found some. They scored a little worse in the depression test than the women who always used condoms.

So was there something brewin’ in the spooin’ that had an effect on their mood? Well, semen does contain several mood-altering hormones, including testosterone, oestrogen, follicle-stimulating hormone, luteinising hormone, prolactin and several different prostaglandins. Some of these have been detected in a women’s blood within hours of exposure to semen!

Also, the question many people will ask is whether oral sex could have the same mood-enhancing effects. The conclusion was that since the steroids in birth control pills survive the digestion process, they would assume that the same holds true for at least some of the chemicals in semen. So next time your lady looks depressed, offer her some man-juice, stat!

So semen is awesome. All hail the semen! Where would semen be without the delivery mechanism? Evolution has fine-tuned the schlong into an efficient tool (ha!) that performs a few really important jobs.


Everyone talks about how hot the mushroom tip penis is. Well, it’s not just the looks. Although, aren’t you tempted to pet it and talk baby talk to it? It’s that darned cute. It turns out that mushroom head serves a very real purpose. Remember above where we talked about goo-glue? The mushroom head is the perfect shape to schlorp (great descriptive word) that goo out from a previous lover so we can replace it with our own. It’s sort of an arms race between lovers.

Wait, size really might matter? Fu… I mean yay, for us hung behemoths! This hasn’t been fully proven yet, but the current theory is that a larger penis has one distinct advantage. According to the journal Evolutionary Psychology, “A longer penis would not only have been an advantage for leaving semen in a less accessible part of the vagina, but by filling and expanding the vagina it also would aid and abet the displacement of semen left by other males as a means of maximizing the likelihood of paternity.”

So the natural followup question is, how big is big enough? The average length of the vagina is four inches. Add in one inch for the outer labia (lips), and your have five inches. The vagina can stretch like an accordion by about one to one and a half inches to accommodate longer penises, but it’s not needed. So the optimal length is 5 to 6.5 inches.

That happens to be the average length of the penis. Anything longer is a waste.

Mental note: Next time I see a male porn star in person (as if), point and laugh at his waste of real estate. Followup mental note: run.

So now everyone who read these articles on the science of semen should be more educated than 90 percent of the population. Go forth and spread the … wealth.

Part 1: Debunking Semen Myths
Part 2: The Ingredients in Semen

Image by John Tann.

Alex Tresor

A bonafide scientist type, doctor-person who’s way too educated for his own good.

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