12 Things Every Man Should Know About Sperm

12 Things Every Man Should Know About Sperm


It’s kind of hard to believe your body creates swimming, gene-toting cells designed to survive in someone else’s body. Not just that, but these are produced in the millions, all day, every day, for your entire life. Whether or not you’re hoping your sperm will make you a dad someday soon, you should brush up on information about these special creations and what yours may say about you. For just that purpose, we’ve enlisted the expertise of Michael Eisenberg, Director of Male Reproductive Medicine and Surgery at Stanford University Medical Center.

10% of Your Genes Are Devoted to Sperm Production

We’re custom-built to reproduce: “There are about 24,000 genes in the body, but in men about 10 percent of those are devoted to sperm production,“ says Eisenberg. This wealth of genes may be part of the reason why sperm vary so much within and between men. With that many genes involved, there is a lot we have yet to learn about the factors that make sperm function the way they do.

A Sperm’s Life Lasts Little More Than Three Months

It takes about two to three months for sperm to fully mature. Sperm begins in the seminiferous tubules in the testes. Once they develop a head and tail, they move into the epididymis, a coiled, 20-foot-long tube located behind the testis. It takes sperm about three weeks to pass through the epididymis, and it is fully mature once it reaches the end. Within a woman’s body, sperm can live for up to seven days. This is important because an egg is available for fertilization for only about 12 to 24 hours after being released from an ovary, and the sperm can take anywhere from half an hour to several days to reach it. This also means that a woman can become pregnant even if she releases an egg days after having unprotected sex.

The Vagina Is a Harsh Environment for Sperm

The average man ejaculates about 3 ml, or half a teaspoon, of semen. This fluid supports the sperm during its journey. “You need a certain amount of ejaculate volume to be able to buffer the harsher environment of the vagina,” says Eisenberg. Some women’s bodies even attack sperm as invaders, causing them to stick together (which inhibits motion), blocking them from the egg, or killing them. This reaction occurs as a result of sperm coming into contact with the woman’s bloodstream, which can happen through injury or infection. If sperm and blood come into contact in a man’s body, he can develop an anti-sperm response as well, but this is very rare.

Nearly Half of All Sperm Never Move at All

When you think of sperm, you think of little swimmers, whipping their long tails back and forth on their race to the egg. Some sperm move this way but many don’t. In fact, rather than judging them for skill or form, fertility standards often look at whether the sperm is moving forward and whether it’s moving at all. On average, only about 50 to 60 percent of sperm show any movement.

Most Sperms are Mutants

A common test used to measure the appearance of sperm, called the Kruger Strict Morphology, says that if 14 percent or more of your sperm looks normal, you have a good chance of fertilizing an egg. If it’s above 4 percent, the outlook is below average but still decent. “When I talk to men and they have 2 percent [normal] morphology, I always let them know that we’re not shooting for the moon with this, it’s a lower orbit where normal is 3 or 4 percent,” says Eisenberg.

Sperm Count Can Say a Lot About Your Health

Beyond fertility, the health of a man’s sperm can be telling of his general health and well-being. “If the overall being is not healthy, I think it can be reflected in its reproductive potential,” says Eisenberg. Reproduction isn’t necessary for survival, so if the body isn’t doing well, it may divert resources away from reproductive organs to other places where they’re more urgently needed. This could result in lower quality sperm. High body mass, poor sleep quality, high stress, cigarette smoking, and heart disease are all associated with lower sperm quality.

What Happens with Age

Men make sperm throughout their entire lives, but sperm quality likely declines with age. As men get older, there tends to be a drop in the volume of ejaculate (but not concentration), percent of motile (moving) sperm, and amount of normal-looking sperm. There have also been some studies that suggest that children whose fathers had them at an older age are more likely to have certain genetic disorders, including autism, epilepsy, and schizophrenia.

What Sperm Should Look Like

The basic parts of the sperm are the head (which holds the DNA), the midpiece (which contains mitochondria that fuel the sperm), and the tail. All of these parts have expected shapes and sizes. In most cases, however, sperm look far from ideal. “There’s a lot of biologic waste in the system,” says Eisenberg. “So, a lot of sperm that we make in general don’t look totally normal, but that’s not necessarily a problem.” Many of your sperm may have lumpy heads, two heads, two tails, or various other issues. Although it may be unsettling, these many deviations are the be-all and end-all determinant of sperm quality.

Sperm Count and Testicular Cancer

Poor sperm counts can be an indicator of testicular cancer later on. Given this all happens in the same area, the association makes sense. However, you shouldn’t feel your fate is sealed just because your sperm quality is low. “It’s important to know that testes cancer is very, very rare,” says Eisenberg. “Less than 1 percent of all men get it.” Also important to know: men who have only one testicle can still be fertile.

Are You Average?

The number of sperm in a man’s ejaculate is a common measure of fertility. This concentration is important, but it can fall within a wide range without being a problem. “The average in this country, interestingly, varies by different regions of the country,” says Eisenberg. “It probably also varies by race or ethnicity.” Average in the United States is around 60 to 100 million sperm per milliliter. Less than 15 million per milliliter or 39 million per ejaculation is considered low.

How to Boost Your Sperm Count

Nothing you read online can take the place of one-on-one help with a medical professional, but there are a few changes we know can help sperm production. “In general, anything that’s good for the heart is good for fertility, but there may need to be some caveat to that,” says Eisenberg. First, eat healthy and don’t smoke. Exercise is usually a great idea as well, except in special cases, such as long-distance cycling. Sperm like to be about four degrees colder than the rest of your body, which is why your testicles hang away from you. When you cram them into tight, hot shorts for a long time, it can affect your fertility. Avoid saunas and hot tubs too if you’re worried about conceiving.

Semen’s Role

You probably already know this one, but sperm and semen are two different things. Sperm are the individual cells that carry DNA intended to fertilize an egg. They are ejaculated with semen, which is everything else that comes out during ejaculation. Sperm’s importance is obvious, but semen plays a vital role as well. “It’s fluid that contains proteins and sugars that allow the sperm to survive in the vagina and give it the energy to get where it needs to go — which is ultimately to the egg,” says Eisenberg.

By Taylor Kubota

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