The Male Reproductive System – Physiology

Remember Eric? Remember Eric’s hypothalamic-pituitary-gonadal axis? Well, that’s sort of where it all begins. The whole thing starts in the area at the base of Eric’s brain called the hypothalamus-pituitary axis, a system of glands, hormones, and chemical messengers called neurotransmitters, all of which are critical for Eric’s reproduction.

$Eric\'s Brain$

Eric’s Brain

Copyleft and © 2002-2008 Steve Cook. Thank you Steve. :)

The first step in Eric’s fertility is him getting ~~horny~~ I mean, aroused, by whatever stimuli. Since Eric is my invention, and as such is like most men I know, then just looking at linoleum will do it for him. :)

Introducing Eric’s Hormones

Ok, now Eric’s seen or heard or felt or smelt or even thought something which works for him (back to the linoleum again), and his hypothalamus gets cooking and produces gonadotropin-releasing hormones (GnRH).

GnRH now make their way (by an anatomical route you really won’t be interested in, trust me) along to the relevant part of Eric’s pituitary at the base of his brain. Like the postman, the GnRH deliver the message to Eric’s pituitary to start producing FSH and LH.

Unlike when the postman brings Eric his bills, Eric’s pituitary responds to this delivery immediately.

So now Eric’s pituitary is doing its thing and producing FSH and LH.

FSH regulates Eric’s sperm production and development (spermatogenesis), and LH stimulates Eric’s other glands to produce testosterone. Testosterone is also necessary to continue Eric’s spermatogenesis, by the way.

Very useful stuff, that testosterone.

Testosterone is produced in Eric’s interstitial cells (Leydig cells) in his testes, and he needs it for his ongoing spermatogenesis. Testosterone is also necessary for developing Eric’s male characteristics, including his muscle mass and strength, his fat distribution, his bone mass, and (surprise) his libidinous linoleum-driven sex drive.

Gosh, where would we all be without testosterone.

Well, extinct, obviously. ;)

Physiology – Introducing Colin The Sperm

Eric’s Testis

So here we are, in Eric’s testes, and his testes have just received an express mail package with a covering letter which essentially says:

Right, come on, let’s go, chop chop, it’s time to get a move on!!

(can I just say here that I’m really glad that Eric’s testes aren’t in Ireland right now, because if they were, that express mail package would likely have either been delayed in the wrong depot with claims of “insufficient address” or “unable to gain access”, or else just totally gone missing, and Eric’s fertility would have ended up being Eric’s impotent sterility. I just wanted to make that clear. Ok, moving on.)

Time: Around 74 days ago – Things are starting to stir…

It’s dark. The postman has just left. It’s just possible to hear the remains of the tune he’s whistling, and the sound of his shoes as he ambulates to the next address. He’s just safely delivered his parcel full of discount mail order hormones, including FSH and LH.

Silence reigns.

In the distance, we hear the opening strains of Richard Strauss’s “Also Sprach Zarathustra“

Deep in the folds of the dark recesses of Eric’s testis, nestled in the curving comfort of his seminiferous tubules, encased in the nurturing, nourishing embrace of his Sertoli cells, an itty bitty baby sperm cell begins to stir.

Anthropomorphically, the little sperm cell (whom you will come to know as Colin), having been there since Eric’s birth, stretches and yawns, as he begins developing and preparing for the journey of his life.

Ok, that’s quite enough of that, thank you. :)

Back To Reality

So, anyhow, it’s 74 days earlier (cos you can time travel in this blog, for real). Eric’s hormones have been correctly delivered to their destination in his testes, and spermatogenesis has begun.

At this point I would like to formally introduce you to Colin, the itty bitty baby sperm cell. I made him up for the same reasons I invented Eric; for ease of explaining, and also just because I liked the idea of anthropomorphically imbuing a sperm cell with a personality (which is more than I can say for…. oh, never mind, moving on). :)

So anyhow, Colin the sperm cell has just started maturing after having been in Eric’s testes all this time since Eric was born.

Colin Stirs

Our Colin began his life partially embedded in nurturing amoebae-like cells known as Sertoli cells, which are located in the lower parts of the seminiferous tubules. Several hundred of these make-up most of Eric’s testicles.

Colin has a shitload of neighbours. He’d better not start playing the tuba anytime soon, or somebody might start complaining.

(or they would, if sperm had ears)

Clumps of tissue surround Eric’s seminiferous tubules, containing interstitial (or Leydig) cells, which manufacture Eric’s testosterone.

Our Colin would be nothing without testosterone.

Literally.

As Colin develops and moves along in the testis, he leaves the comforting nourishment of Eric’s Sertoli cells in the lower part of his seminiferous tubules behind. Now Colin is going to live in his new home in the upper part of the tubules. It’s more expensive, but the neighbourhood is better.

Young sperm cells (like Colin is at this point) are known as spermatids.

Colin Gets Promoted

After awhile, our Colin develops a head and tail, although he’s not yet ready to go play with the grown ups. But he has grown up a bit, so he gets promoted along with all the others in his class, and they all straggle along into an area of spongy tissue on top of Eric’s testis called the epididymis, which is a 20 foot long scrunched-up tube. Colin’s journey through Eric’s epididymis will take about three weeks.

But Colin doesn’t know any of this. All he’s worried about is if any of the other Colins got more fructose than he got. Cos Colin’s getting a bit cranky, what with all these hormones, not to mention all the anthropormorphising I’m doing, by making Colin into a cranky adolescent spermatid.

Colin and his buddies are carried along in this fluid which is rich in fructose. They all get their energy from this as they mature. They might possibly squabble over who gets more of it.

Early on in Eric’s epididymis, Colin and his pals make a really poor showing at the disco, since none of them can move in a forward direction. All they can do is weakly vibrate their tails. But Colin won the prize for his weak tail vibration as “Best Newcomer Spermatid, 2008”.

However, by the time Colin and his classmates have reached the end of Eric’s epididymis, they’re all growed up and can strut their stuff with all the best wriggly sperm.

Now Colin has a head which is packed full of Eric’s DNA, and a tail which lashes and bashes and crashes back and forth fast enough to swoosh himself forward by his own length every quarter of a second. That’s pretty fast.

Time: 74 days later – The Present

Colin da sperm is in da house.

Eric’s Penis

Physiology – Eric Does Linoleum

So Colin’s all growed up and ready to go, and Eric has been looking at linoleum again and is feeling pretty chock full of hotness.

Eric’s Linoleum Penis

This hotness was accompanied by the release of GnRH, which in turn has triggered the release of FSH and LH, which in turn has triggered Colin to go ahead and develop, or, spermatogenesise (or, Colinogenesise).

Yes, I made those words up. Deal with it.

Just in case you’re wondering, this all happens just a bit rapidly, much quicker than I can tell it.

Colin Leaves Eric’s Epididymis

Eric’s Reproductive System

So, Eric’s feeling pretty hot, what with all that linoleum and everything, and what happens next is that his central nervous system is triggered, which in turn triggers a bunch of his muscles to contract.

And the result of that is, that Eric’s testes are drawn up closer to his body, and the contracting muscles in his epididymis shoot Colin and his mates out into Eric’s vas deferens, much to Colin’s amazement.

But Colin’s a game wee sperm, and never once said “Hey! I wasn’t ready!”

Eric doesn’t care about Colin at this point, he’s much too busy getting hot over the linoleum catalogue.

Eric is strange. Let’s just accept that, shall we?

When Eric experiences sexual excitement (like now), his nerves stimulate a bunch of his muscles to contract, which pull Eric’s testicles up closer to his body, and also force Colin and his buddies out into one of two rigid and wire-like muscular channels, called the vasa deferentia. (A single channel is called a vas deferens.)

All the Colins are propelled up Eric’s vasa deferentia by muscle contractions triggered by sexual activity. Colin moves up through the vas deferens from Eric’s epididymis into Eric’s pelvic cavity, around his urinary bladder, and along to his seminal vesicles. Each of Eric’s vas deferens joins one of his seminal vesicles to form his ejaculatory ducts. Eric’s seminal vesicles contribute fluid to the sperm. Eric’s vas deferens also collects fluid secreted from the nearby prostate gland later on.

(waves to Colin)

So, there’s all kinds of fluidy stuff happening in Eric’s reproductive system right now. His prostate will be swelling, which will be noticeable to any gloved fingers which might have innocently wandered into the area. ;)

Why Eric’s Urethra Cannot Multitask

At the same time that Colin is travelling up Eric’s vas deferens, Eric’s prostate will have closed off urethral access to the urinary bladder with a sphincteral muscle ring. I personally can’t prove it (what with not being a doctor or anything even close), but I’m fairly sure there is a relationship between when that happens and the secretion of pre-ejaculate.

Eric’s bulbourethral glands, or Cowper’s glands, are pea-sized structures located alongside his bulbous urethra just below his prostate gland. These glands produce a clear, slippery fluid which empties directly into Eric’s urethra. This fluid lubricates his urethra, and neutralizes acidity from any residual drops of urine.

(or, in other words, Eric’s pee is acidic enough to kill Colin stone dead. This is why it’s so important that pee and semen don’t co-inhabit Eric’s urethra)

The clear slippery fluid secreted by Eric’s bulbourethral glands might be recognised by some as pre-ejaculate, or Eric’s “pre-come”

Eric’s urethra serves as a conduit for both urine and semen. But one of the functions of Eric’s prostate is to ensure that his urethra will only carry one at a time, and never both simultaneously.

(what with the killing Colin stone dead and all)

During heightened arousal, Eric’s prostate tightens that smooth muscular sphincteral ring around his urethra, thereby isolating his urine and urinary bladder from any Colins who might be innocently hanging out in the vicinity. As a result, Eric’s urine cannot enter his urethra when his arousal has been all heightened up by that damned linoleum catalogue.

And thus, Colin is saved. :) (for the moment, anyhow)

So, I mean, why would Eric’s bulbourethral glands be preparing his urethra for the safe passage of all the Colins by neutralising any acid from urine, if Eric could still pee after the his pre-ejaculate entered his urethra, but before Colin’s arrival there?

So I’m going to conclude that Eric’s prostate tightens that smooth muscle ring cutting off access to his urinary bladder, and then his bulbourethral glands start secreting their viscous alkaline lubricant.

In that order.

If anybody has any objections to that conclusion, please leave a comment including your reasons for the objection. Thank you. :)

Anyhow, back to Eric’s excitement (cos, you know, it’s really hard to find aroused excited males, right? ;) ).

Colin Chills Out In A Hot New Night Spot

So all the Colins wriggle up the vasa deferentia into Eric’s pelvic cavity, over and under some stuff, passing the seminal vesicles before heading for the ejaculatory ducts just behind the base of Eric’s bladder.

Then Eric’s seminal vesicles produce fructosey, alkaliney goodness which Colin and his chums chow down with relish (and maybe also some ketchup) before they energetically swim into the hottest new night spot in town, the ejaculatory ducts.

All the Colins will hang out there and strut their stuff til just before Eric ejaculates.

A Polo Mint

© Nestec SA

Eric’s prostate gland (which feels like a polo mint) has been swelling up with seminal fluid all this time, which can clearly be felt by any gloved fingers which might happen to be around.

Because of Eric’s prostate closing off urethral access to the bladder with that smooth ring of muscle thingy, a separate personal private duct system connects Eric’s prostate directly to his bulbous urethra.

As Eric gets increasingly turned on by the utter hotness of his glossy new linoleum catalogue, his hotness leads him closer and closer to his ejaculation. All Eric’s fluid builds up pressure around the place, and this triggers all the Colins to squirm out of Eric’s ejaculatory ducts into Eric’s bulbous urethra.

Eric’s prostate contributes additional nutritional alkaliney goodness for Colin through the personal private prostate ducts, and this all combines to make a bunch of semen in Eric’s bulbous urethra.

Or, if he’s one of us, then he’ll more than likely be imagining what he wants that linoleum to do to him.

Eric’s prostate surrounds his ejaculatory ducts, as well as his urethra. So in addition to his prostate swelling with its own content of seminal fluid, his prostate also enlarges around his swelling ejaculatory ducts as they fill with the growing amount of semen Colin’s hanging out in. This all makes the prostate easier to feel, and also much easier to gauge the level of Eric’s excitement, depending on the relative size of his prostate at any point in time.

Eric’s prostate really does vary quite significantly in size from his pre-linoleum-droolfest to the moment of ejaculation. I’m sure you’ll find it quite considerate of Eric’s prostate to do that for you. :)

(I really wanted to use the word “squirtaciousness” here, but I just couldn’t bring myself to do it. But it was such a great word, I had to mention how I wasn’t mentioning it. I hope you understand.)

Eric’s Past The Point Of No Return

So, right now we’re at the stage where Eric is so turned on that he’s just going to have to ejaculate. All the Colin-fluid is muscularly propelled along from Eric’s ejaculatory ducts into his bulbous urethra.

Colinless seminal fluid from Eric’s prostate flows through its personal private prostate ducts straight into Eric’s bulbous urethra, increasing the volume of Colin juice by quite a lot actually.

(about 60%)

Then everybody is propelled from Eric’s bulbous urethra by all sorts of yummy muscular contractions, through Eric’s urethral channel and out the tip of his penis.

That is, unless you’ve milked Eric, in which case Colin sweetly exits the tip of Eric’s penis, after slowly draining from Eric’s bulbous urethra, propelled along only by the gentlest of muscular ripples, gravity, and your finger running up the underside of Eric’s penile shaft.

I know which one I like the sound of better. ;)

And then it’s nap time for Eric, because his body will enter the post-orgasmic exhausted state known as the refractory period (unless somebody is around to make him stay awake).

However, if Eric has been milked, then he will not experience the refractory period, or at least, he won’t experience it anywhere near as intensely.

A milked Eric will be entirely more likely to stay awake after all the Colins have vacated the area, than an Eric who has ejaculated with strong muscular contractions.

Interesting things to note and learn. :)

Meanwhile, Colin, the 74 day old sperm, dies heroically, trying desperately to fertilise a hanky.

So, the average Colin spends a total of about two and a half months making the journey from the beginning of spermatogenesis to Eric’s ejaculation, in the sole hope of fertilising a woman’s egg. Throughout the journey, Colin and his Coliny pals live more or less independently of Eric, on a continual sugar high from the fructose in the semen.

It wasn’t Colin’s fault that Eric aimed him at a hanky. :) I suspect that aim is a rather significant issue most days. :p

So What’s Next?

If you had any difficulties with any of the material on this page, I’ve done you up a hugely abbreviated and seriously summarised version, because I really feel that you’ll need at least a basic understanding of what goes on inside Eric when you milk him.

If you feel confident about your understanding of the stuff here, then the next thing is probably to have a look at the page with details of the structure of the anus and rectum.

Enjoy. :)