There’s a vas deferens between your epididymis and your ejaculatory duct

vas deferens mnemonic with Prof. Sperm at the chalkboard

You’ve almost made it through a semester of anatomy.  Like a sperm cell, you sometimes feel like just another face in the crowd, but you know there’s light at the end of the tunnel!

But first, you need to make sense of that tangle of tubes known as the male reproductive system.

The epididymis – which rhymes suggestively with “did he miss” – is the site of final sperm maturation.  Twenty feet of tiny tubing is coiled so tightly it fits in a structure less than two inches long, that hangs like a comma over the testis.  The epididymis is also where the sperm bide their time until ejaculation occurs.

But most of the semen is not sperm, and is instead produced by glands, found further down the assembly line.  The seminal vesicle, in particular, plays a seminal role, producing 60% of the semen, a concoction of nutrients, signals and other molecules.

On Professor Sperm’s chalkboard diagram, the ejaculatory duct represents the confluence where the wriggling sperm are doused with this sticky cocktail.  Other glands down the pipeline (prostate and bulbourethral glands) complete the mix, as it travels through the urethra on its way to the exit.

If all those tubes are starting to sound alike, take heart!  Between the epididymis and the ejaculatory duct, there’s truly a vast difference, and also, a vas deferens.  This longest of the male tubes (18 inches or so) is called into play only at the time of ejaculation, transporting the sperm all the way up the scrotum, along the inguinal canal and finally hurtling them into the ejaculatory duct.

In place of “vas deferens”, many books now use the term “ductus deferens”.  To that, I say, “same difference!”

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