Medical Fun Facts Podcast

MFF0010: Is it sperm or semen?

Why do people say sperm when they mean semen?

Content Notice: Strine used.

You often hear people say sperm. What is sperm?

A sperm is a bloke’s reproductive cell. If it’s motile it’s a spermatozoon (spermatozoa plural) and if it’s not motile it is a spermatium. Human sperm cells have 23 chromosomes and can join with the 23 chromosomes in a sheila’s egg cells during fertilisation.

Semen or seminal fluid may contain sperm or spermatozoa and it’s secreted by our sexual organs. Now I say may, because you can still produce semen if a bloke has had a snip job (vasectomy) or been castrated (orchiectomy or orchidectomy).

So when you ejaculate, sperm passes from the testicles through the ejaculatory ducts and mixes with fluids from the seminal vesicles, the prostate and the bulbourethral glands to form semen. If you don’t have any sperm during ejaculation your semen is the fluid from the seminal vesicles, the prostate and the bulbourethral glands but without sperm. The seminal vesicles produce most of the fluid in semen and it’s yellow and viscous. The prostate provides a clear or whitish fluid which contains a range of good stuff. The bulbourethral glands produce a thin clear lubricant for the urethra.

The average volume of semen in a man’s ejaculate is 3.4 mL.

Did you know milt refers to the male genitalia of fish which contain sperm and are used as food?

Did you know that a 24-hour culture of Hæmophilus influenzæ on chocolate agar smells like stale semen? I remember when I was learning to read the respiratory plates as a boy, the scientist teaching me reckoned Hæmophilus influenzæ smells like semen the following morning. I told her I wasn’t in the habit of sniffing stale semen. So if you’re a budding microbiologist and you’re in the habit of disregarding modern work health safety regulations about sniffing agar plates let me know what you think.

And one last thing which I think is a fact but it may be just one of those internet things. Apparently, the first director of what is now MI6 (the UK’s international intelligence service), a man with an apt name, viz., Sir Mansfield George Smith Cumming noted every man is his own stylo (short for stylograph) because semen apparently can be used as invisible ink.


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