Here’s a million dollar question: From whence does the ejaculate come? The word “semen” is actually Latin, derived from “cemani” meaning “juice.” Great, Doc, but where does the juice actually come from?
A Complex Sauce
Fluids from several different body organs mix and mingle before being expelled as ejaculate. The much-maligned prostate, a reliable cause of urination issues with age, is actually important for normal, fertile semen. It secretes a clear, acidic fluid in small amounts (10% of total volume) that comprises the first part of the ejaculate. Sperm, whose reputation far exceed their size, enter the fluid fray after being pumped all the way from the scrotum (i.e. the epididymis to be exact) through the muscular vas deferens and into the ejaculatory duct within the prostate, like a bullet being loaded in a chamber. The seminal vesicles, which you likely have never heard of and have no idea that you actually had, hold most (80%) of the sugar-rich seminal fluid and push the sperm pellet into the urethra and, eventually, out into the world.
But it gets even more complex than that. Think of the ejaculate as the opposite of epoxy glue: instead of two liquids mixing to become a solid, semen is first delivered as a sticky semi-solid, and after mixing, liquefies over time. It is only after semen becomes fluid that that sperm are released to go forth and conquer.
When Sex Kills
Geez, why all the anatomical muss and fuss just to ejaculate? Because, in many species, males must get out of Dodge as soon as their work is done as females immediately turn predatory on their sexual partners. They don’t call them “praying mantises” and “black widow spiders” for nothing. When sex is life threatening, evolution has its way of getting that sperm dollop to stick where it’s planted inside the female before all hell breaks loose.
Good for Men
Observing changes in the ejaculate also helps us take care of men. A low ejaculate volume is characteristic of ejaculatory duct obstruction or absence of the vas deferens. A dry ejaculate often indicates retrograde ejaculation. Blood in the ejaculate, termed hematospermia, may be alarming, but is usually benign. And don’t worry, guys, nobody can tell that you had a vasectomy as it causes no detectable change to the ejaculate.
Now how’s that for mixing fun, fertility and science? Pretty natural thing to do, according to the poet Ralph Waldo Emerson, who said: “Men love to wonder, and that is the seed of science.”