Back to Basics With Semen: What It Does and How It Looks

The origin and purpose of semen are probably among the most misunderstood concepts in the history of humankind.

For instance, in the 4th century B.C.E., Greek philosopher Aristotle believed men generated heat inside their bodies to change blood into semen when the time came.

In the 15th century, Italian scientist and artist Leonardo da Vinci theorized there was a channel inside the penis that connected directly with the base of the spinal column and, from there, to the brain. This was in keeping with the then-current idea that semen originated in the brain.

Individual sperm cells were first viewed in the 17th century by Dutch merchant and amateur scientist Antony van Leeuwenhoek. He spotted the little swimmers when he rushed over to his prototype microscope with a handful of semen immediately following sex with his wife.

Unfortunately, van Leeuwenhoek concluded that spermatozoa were just parasites that had invaded his precious semen, a belief that prevailed until well into the 1800s.

Before we get too smug about how much smarter we are today, let's not forget there's still a lot of confusion about semen. This includes beliefs with little or no scientific grounding, such as:

• Semen does wonders for your skin.
• It is good for your hair and teeth.
• Retaining semen and declining to ejaculate boosts your testosterone, gives you more facial hair and makes women flock to you.

What does semen really do, anyway? We'll examine how the essential fluid is produced and discuss certain qualities of semen, such as consistency, smell, color, volume and more.

What does semen do?

Semen is the whitish, opalescent fluid a man expels when he ejaculates. It's responsible for providing nutrition, fuel and protection for sperm cells as they make their journey to connect with a female's egg and initiate conception.

The environment of the vagina is slightly acidic, and sperm cells need a more basic pH environment, so semen is more of a base—the opposite of an acid. That's in order to ensure the sperm cells live long enough to have a chance to fertilize the egg.

Some of the basic components of semen include the following:

• Fructose (provides energy to the sperm)
• Amino acids
• Potassium
• Prostaglandins (hormones to suppress the woman's immune response against "invading" semen)
• Zinc
• Potassium
• Protein-splitting enzymes
• Spermatozoa (sperm cells)
• Mucus and galactose (provide lubrication to help sperm along)

How is semen produced?

We often think of semen as a product of the testicles, and of course, it's true that sperm are produced there. But the actual sperm make up a mere 2 percent to 5 percent of the total volume of semen. There's a whole lot more going on in the semen factory that is the male reproductive system.

"The sperm is created in the testicle, and it's a reproductive cell with a life cycle of about three months," said Neel Parekh, M.D., a men's fertility and sexual health specialist with Cleveland Clinic. "It takes about three months for the sperm to reach its final form in the testicle. From there, it travels through the seminiferous tubules, which are in the testicles, and goes into the epididymis."

The epididymis is the long, tightly packed, squiggly tube that arises from the upper back part of each testicle to carry the maturing sperm to the next staging area in its journey.

"As it travels from the head of the epididymis to the tail of it, that's where it gains its motility, its ability to swim," Parekh said. "The epididymis turns into the vas deferens, and that's the tube that carries the sperm to the ejaculatory duct, where it joins with the seminal vesicles. That's where the majority of the fluid in semen arises from, where fructose and other nutrients are produced. Then the vas deferens and the seminal vesicles come together in a confluence called the ejaculatory duct, and from there, it's expelled into the urethra."

Sounds exhausting—until you think about how easily it can happen sometimes. Then there are the contributions to semen that come from the prostate gland (25 percent to 30 percent of the volume) and the bulbourethral glands (less than 1 percent).

Semen appearance

The appearance of semen can vary wildly, and probably the first thing most guys notice is the volume of the ejaculate.

Volume

Semen volume can be a big concern for some guys.

"I spend a lot of time explaining to guys that it's not like in porn," Parekh said. "The amount of volume that's normal is 1.5 milliliters."

Normal volume from ejaculation can range anywhere from 1.5 mL to 5.0 mL, which is still a much smaller amount than you might think.

If the amount of fluid is consistently very low—less than half a teaspoon—it could indicate a blockage or point to retrograde ejaculation. For the most part, though, your diet, hydration and frequency of ejaculation are going to be the main factors that determine semen volume.

Color, consistency and odor

The color and consistency of semen can also cause concern for some guys. Know, though, that they vary a lot naturally and because of environmental factors.

"Typically, color and consistency are more an indication of diet as opposed to anything worrisome," Parekh said. "Consistency varies a lot from guy to guy. Sometimes it can be watery, or today I had a guy tell me it was like Jello. So it can vary a lot and, typically, that's affected by diet, hydration and whether they smoke."

It's normal for semen to quickly devolve to a more liquid state after being exposed to the air for 15 to 30 minutes. An interesting theory on semen consistency is that the way semen coagulates is an evolutionarily useful adaptation. The idea is that while the first part of the ejaculate remains more fluid and mobile, the latter part coagulates quickly to help keep the liquid stuff in place long enough to reach the egg.

Usually, semen has a slightly bleach-like odor and a variety of shades, ranging from bright white to yellowish to grayish. If you notice your semen has a strong, foul odor or it's brownish or reddish, it could indicate a sexually transmitted infection (STI) or a condition called hematospermia, in which blood is mixed with the semen.

Conclusions

It's no mystery why people from ancient times to those living in the present day were and are fascinated with semen. It's rather an important substance, after all.

Understanding the details of what it does, how it's produced, and what is considered the normal range for volume, color, smell and other parameters can, hopefully, help guys to be more realistic about it; maybe even enabling them to recognize when there might be a problem.

If you do have any questions or concerns, a conversation with your healthcare provider is always advised. Don't have a doctor you see regularly? You should. Fortunately, telehealth makes it easy to connect with a professional who can answer your questions and evaluate your situation. Many physicians offer video visits, which are a good 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, including men's health.