What Is the Difference Between Semen and Sperm?

When we were growing up and learning about the mysteries of human sexuality—often from friends who were as misguided as we were—no doubt we all harbored some insane ideas. One question we probably all had, for example, was what is the difference between semen and sperm?

Some mysteries of male sexuality continue to confuse people, even a lot of adults. Take semen and sperm, for example. Confusion can include mistakenly using these words interchangeably, even though they're not the same thing.

For starters, there's much mythology surrounding the "stuff" that comes out of the male sexual apparatus. Much of it is laughable. Among other things, semen is claimed to be good for your skin, treating a sore throat, preventing cavities and, somehow, even for treating depression when a man ejaculates during unprotected penis-in-vagina sex.

Let's take a look at some of the facts about semen and sperm.

What is semen?

Semen is the thick, whitish, pearlescent liquid that men discharge from their penises when they ejaculate. At various times, it can appear watery, thick, yellowish or even have a red or brown tint. The latter may indicate a medical condition called hematospermia, or blood in the semen.

Made up mostly of water, semen typically contains nutrients, a little zinc and a bunch of other substances. Most importantly, the purpose of semen is to carry the man's reproductive material: sperm.

The actual spermatozoa, or sperm cells, comprise a minority of the volume of semen. The 15 million to 200 million sperm per milliliter (mL) ejaculated in semen account for about 2 percent to 5 percent of the ejaculate.

"Semen is basically fluid that includes the proteins, nutrients and enzymes that are all necessary to allow the sperm to survive," said Neel Parekh, M.D., a men's fertility and sexual health specialist with Cleveland Clinic. "Without the semen, the sperm wouldn't make it to the egg. When all this gets to the egg, that's where the sperm's purpose is, and that's to fertilize the egg."

A big reason sperm never travel solo and roll only with a whole bunch of muscle is they're heading to a neighborhood, so to speak, where they need protection. The environment of the vaginal canal through which sperm must travel to reach an egg and fertilize it is opposite to what sperm need to thrive.

"The vaginal canal is more acidic, while the semen is more alkaline," Parekh explained. "When we get a semen analysis, one of the things we check is the pH, or the acidity of it. If we find that it's very acidic, that could be a sign that there's a blockage, meaning that the fluid from the seminal vesicle isn't making it into the semen because the fluid from the seminal vesicle is very alkaline. That's what gives the semen its alkalinity."

Semen's slightly alkaline pH is typically between 7.2 and 8.0. Pure water is considered to have a neutral pH of 7, for comparison's sake.

A woman's vaginal canal, on the other hand, typically has a more acidic pH of between 3.8 and 4.5, if it's healthy. The semen's job, then, is to protect sperm by using its slightly alkaline pH and provide nutrients to give the sperm cells the energy they need to make the journey up through the vaginal canal to reach an egg and fertilize it.

What's in semen?

If all is well and the man is healthy, a semen sample should be packed with sperm cells, the little tadpole-looking organisms that squiggle and squirm and swim their way up the vaginal canal to try to reach an egg.

Medical guidelines typically point to a healthy range of 15 million to 200 million sperm per mL. A sperm concentration of less than 15 million per mL, or a total sperm count of fewer than 39 million per ejaculation, is considered low.

But again, sperm, which come from the testicles, represent just 5 percent of the total volume of semen, or even less. So what else is going on in there? What's joining the sperm cells on their quest?

The seminal vesicles provide about 60 percent of the volume of semen with the following:

• Fructose (provides energy to the sperm)
• Amino acids
• Citric acid
• Phosphorus
• Potassium
• Prostaglandins (hormones)

The prostate gland provides about 30 percent of semen's volume with the following:

• Citric acid
• Calcium
• Sodium
• Zinc
• Acid phosphatase
• Potassium
• Protein-splitting enzymes
• Fibrinolysin (an enzyme)

From the bulbourethral glands, semen picks up less than 1 percent of its volume in the form of the following:

• Galactose (a simple sugar)
• Mucus (provides lubrication)
• Preejaculate (provides lubrication and neutralizes the acidity of any residual urine in the urethra)
• Sialic acid

What is the difference between semen and sperm?

While semen and sperm are related, it's clear they aren't synonymous. Semen contains sperm, not vice versa.

One way to remember the difference is to remember that we often talk about spermatozoa "swimming." So if sperm swim, semen is their favorite pool.

If you set up an appointment with a fertility specialist with any questions about your semen or sperm, they may suggest a semen analysis. After all, it's better to know what's going on rather than worrying when there might not be anything wrong at all.

Chances are you don't have a fertility specialist in your contacts list. Fortunately, telehealth makes it easy to connect with a doctor who can answer your semen and sperm questions and evaluate your situation. Many physicians offer video visits, which are an excellent way to see a doctor quickly since a lot of them have same-day appointments. Giddy telehealth is an easy-to-use online portal that provides access to hundreds of healthcare professionals whose expertise covers the full scope of medical care, and if labwork is warranted, they can help you set it up.