Ejaculation Process
THE EJACULATION PROCESS
is really all about sperm.
But only in the sense that the greatest percentage of seminal fluid is designed to deliver and to protect a relatively miniscule percentage of actual pay-load. Sperm constitute only about 5 % of our total ejaculatory fluid output.
The average healthy, fertile male produces 2.0 – 6.0 ml of ejaculate. This converts to close to 2.00 – 6.00 cubic centimeters. If you happen to average in the 4.0 ml range, this is a bit less than 1 teaspoon. However, within each milliliter of seminal fluid, assuming it were well-mixed (and it is not when it first leaves your body), there can be as many as 100 million sperm.
Q: How come we don’t just ejaculate pure sperm?
A: Because if we did they’d die on the way out and there wouldn’t be any people around to have sex with.
Our reproductive system also functions as our liquid waste disposal (urine travels the same channel out as sperm do – through the urethra), therefore we need a rather complicated series of back-up glandular functions to assure the safety of sperm on what would otherwise be a treacherous trip into a vagina. Urine is acidic and deadly to sperm. Our urethral linings are normally highly acidic because we pee far more often than we cum, whereas sperm thrive in alkaline environments. How then to get sperm safely out from Point T, the testes, to Point V, the vagina?
The first line of sperm defense is the Cowper’s glands. We have two of these. They are pea-sized and nestle below the prostate on either side of the urethra, into which they drain. When we become somewhat sexually excited, the Cowper’s glands activate and drip into the urethra, bathing it with a few drops of a clear, slippery, alkaline fluid we call “pre-cum.” This neutralizes the acid lining of the urethra and eventually becomes another 5 % of our total seminal fluid output.
But let’s not get ahead of our story. Many perils yet face the sperm, which have not even begun to move from their storage place, in the epididymis.
Most of us assume that our testicles manufacture fertile, active sperm, which we then ejaculate, along with some other fluids. This is only partly true. There is a very critical, long (about 6 meters, or 18 feet fully extended) and yet tiny tubular organ called the epididymis outside each testicle and attached to it. The spermatozoa produced within the testicles (at the normal rate of 50,000 an hour) are immature, usually non-motile, not even fully-formed. Without the epididymis, we would be largely infertile. During sperm production, the testes move the “incomplete” sperm to the epididymis along with a relatively large amount of water. Much of this water is removed by the epididymis as the sperm are concentrated there. Mature sperm will remain in the epididymis for up to 60 days, depending on the number and the frequency of ejaculations that occur.
Q: What if we don’t ejaculate for over 60 days? What happens to all those sperm then?
A: If you were to wait that long without masturbating or having sex, you would likely have an involuntary ejaculation during sleep during that period. If you didn’t, the most mature sperm would be metabolized by your body.
It is inside the epididymis that sperm maturate, are concentrated, and through a series of complicated hormonal “baths,” become viable and increasingly motile. They are stored, waiting as it were, before they begin to move up the vas deferens on their way out through the urethra as ejaculation approaches.
The vas deferens (we have two of these) extend from the epididymis to the prostate; they are about 8 inches long. These tubes are capable of contracting during ejaculation, propelling the sperm on to meet up with other fluids. During vasectomy, a small section is removed from each of these tubes, preventing sperm from joining the rest of the ejaculate fluids. Thereafter, for the “clipped” guy, total ejaculate fluid only decreases by the small amount that is comprised of sperm, about 5%.
Meanwhile, other important sexual accessory glands are constantly doing their own work toward the moment when we will ejaculate, even while we are contemplating our navels, sleeping, or washing our cars.
The Seminal Vesicles, which reside above the prostate, and against it near the base of the bladder drain into the vas deferens then the urethra, independent of the prostate’s own fluid. The vesicles produce about 70 % of total ejaculate volume. Their contribution is a complex mix of fructose, prostaglandins, spermine, citrate ion and more, all of which serve to further mobilize and nourish the sperm when they come into contact with it just a bit further down the urethra during ejaculation. The vesicles also produce androgen-dependent proteins. These cause the clotted or “clumped” areas in the ejaculate you see when you masturbate. The seminal vesicle fluid portion is thick and alkaline.
The prostate gland is about the size of a walnut and is seated just below the bladder neck. The urethra begins at the bladder neck and runs smack through the middle of the prostate. (This is why we have trouble peeing when we have a prostate inflammation.) The prostate creates about 10 percent of ejaculate fluid, sometimes more. High in citric acid, choline, and zinc, this fluid is watery, grayish in color, alkaline, and opaque. It is suspected that prostatic fluid contributes to the later liquefaction of clotted ejaculate, a process which occurs as proteins break down over a period of about twenty minutes after ejaculation. You’ve probably noticed when removing a condom sometime after intercourse, or after dozing following ejaculation that the original, thicker puddle on your abdomen has become quite watery. During this protein-breakdown stage, all of the various glandular contributions do finally mix and very well. The same protein breakdown occurs to ejaculate within the vagina.
As you’ve seen, all these accessory fluids contributing to total ejaculate are alkaline. Not only does this alkalinity protect sperm through the acid environment of the urethra, but also within the vagina, which is an acidic environment as well.
Q: I’m getting bored. I have all my stages set and lit. All these fluids are at the ready. So what starts the good stuff happening?
A: A thoughtful, impatient, and very complicated question. For our purposes, here’s the shortest answer.
When you are having sex or masturbating, you move through stages which Drs. Masters and Johnson broke into four distinct ones: Excitement during which you get an erection; your blood pressure, breathing, and heart rates increase, your testicles tighten closer to your body, your nipples may become erect, your torso skin may even redden. (This happens to women more often than men).
Then you move into what they called somewhat abstrusely the plateau during which heart, blood pressure, breathing rates increase even more. The testicles may pull up tighter toward the pelvic wall. The glans of the penis may redden deeply. If they haven’t already made an appearance, clear, slippery drops of pre-cum manufactured by the Cowper’s glans arrive at the meatus, the end of the urethra. Still, even though you are getting close, you are not quite ready to cum.
What tips you over the edge (orgasm stage) and into ejaculation is a highly orchestrated series of events broken further into two sub-stages beginning with the “emission” stage. This is when things begin to move along their pathways but during which the “moment of inevitability” (you know you are going to cum no matter what you do) hasn’t quite arrived.
Mature sperm stored in the epididymis on each testicle move out into the vas deferens and around, then down to the urethral bulb which holds them and enlarges as they accumulate. This is what Masters and Johnson refer to apparently as “emission” in this context. As sperm do accumulate, you feel the beginning sensation that you are going to cum. Two sphincters close: at your bladder neck to prevent retrograde ejaculation into the bladder; another sphincter closes just below the prostate, trapping sperm within the urethral bulb. [Some sperm may have been propelled farther forward from the bulb and up through the urethra by the fluid from the Cowper’s glands which is already moving, to mix with that. (For this reason, women can become pregnant via vaginal contact with pre-cum alone.)]
As the urethral bulb fills, all accessory gland functions very rapidly shift into high gear for the expulsion stage or orgasm. The vas deferens begin to contract, forcing even more sperm toward the urethral bulb. The prostate begins to contract expelling some of its own fluid, the seminal vesicles contract. A substantial amount of seminal vesicle fluid (remember that this comprises most of your ejaculate volume) joins with the prostate fluid and arrives at the urethral bulb to converge with the hundreds of millions of sperm already collected there. Fluid “clumping” is immediate. The bulb contracts, as does smooth muscle along the shaft of the penis, pressing fluids rapidly outward. Since this is all happening at the rate of about 35 miles per hour within an area smaller than your spread fingers, you are now powerless to do anything but… shoot.
The first expulsion of fluid from the meatus contains more sperm than subsequent ones. Each successive contractual wave – they occur 0.8 seconds apart - contains less sperm and more (by relative volume) seminal vesicle and prostatic fluid. As you deposit your ejaculate in the vagina, and thrust while doing that, you tend to mix a bit better what was not a perfect mix to begin with. Never mind. The process of protein breakdown will liquify the entire ejaculate. Your safely alkaline, fructose, sperm, prostaglandin, etc, etc, contribution to the perpetuation of the species has been delivered.
Resolution
This is the last of the four stages of sexual response, as defined by Masters and Johnson. During the resolution period, your orgasmic contractions become weaker, then end. Some fluids continue to ooze from the urethra. By now your pituitary gland (way up there in your brain) has signaled that prolactin levels must increase sharply. Prolactin causes your erection to deflate and you tumble, very often gratefully, into what is called the “refractory” period during which you usually can’t get hard again for some period of time ranging from minutes to hours, or days, dependent primarily on aging factors.
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