Life's Journey Under the Microscope. How Long Do Sperm Live?

Stages of sperm development

Spermatogenesis

Before we answer the question of how long sperm live, let's discuss the process of their creation. Sperm are created in the seminiferous tubules of the testicles. The temperature in the scrotum is 2 to 3 degrees Celsius lower than in the rest of the body, which is important for the proper course of spermatogenesis . This is the process of sperm maturation, lasting from 72 to 74 days, which begins at puberty and can last until old age. Once the sperm reaches its final form, it learns to move in the epididymis (the reservoir of the upper surface of the testicle) for another 10 to 12 days, so that after ejaculation and entering the vagina , it can efficiently pass to the egg. However, if they do not wait for ejaculation for a longer period of time, they degenerate and disappear.

Sperm structure

Wait a minute. What is a mature, complete sperm? Everyone knows what a male gamete looks like, but do we know what functions its individual elements perform?

A sperm is about 20 times smaller than a female gamete, which we would be able to see with the naked eye. The volume of a human sperm is between 20 and 40 µm³ (it is even smaller than a red blood cell – its volume is close to 100 µm³), but despite its microscopic size, it is divided into 3 important parts:

• the head , consisting of genetic material and a cap, which enzymes allow to break through the wall of the egg cell;
• the insert , or neck, containing mitochondria, which are the source of energy;
• tail , which is responsible for the sperm's motility.

It’s worth knowing, though, that not all sperm are built the same. Many have defects—multiple heads, oddly shaped tails, or missing parts—that make them simply unsuitable for their journey through the female reproductive system.

Environment and sperm viability

Elimination path to the egg

How long do sperm live in the vagina?

When trying to reach their destination, sperm undergoes elimination not only because of their shape, but also because of their mobility. Many factors negatively affect sperm quality, which I will discuss in a separate paragraph. On the other hand, sperm released during ejaculation can reach speeds of up to 45 km/h. A good pace, but also a long way to go. The vagina-cervix-fallopian tube-egg route is about 15 centimeters long. The first section is the most demanding for sperm. The acidic environment of the vagina is actually toxic to male gametes (the optimal pH for sperm viability is 6.5 to 7, and the normal pH of the vagina is in the range of 3.5 to 4), but semen and cervical mucus change its pH to a more alkaline one.

Cervical mucus, exactly! I have already written extensively about it on our blog and mentioned, among other things, that it plays a significant role in the transport of healthy sperm. Thick, post-ovulation mucus blocks the sperm's path to the egg, while the one close to ovulation, i.e. watery, stretchy and clear, is like a highway leading to it. And those sperm that do not immediately encounter an egg on their way can survive for 3 days in the crypts of the cervix, thanks to the mucus flowing out of it (at a convenient time, stronger sperm can survive up to 5 days). The cervix is ​​therefore a reservoir for sperm, from which viable sperm are gradually released into the fallopian tube.

The extended life of sperm thanks to mucus means that the fertile period of people with uteri is not limited to the day of ovulation . Even if intercourse takes place a few days before ovulation, there is a good chance (the highest from 48 hours before ovulation to 24 hours after ovulation) that fertilization will occur. This is because the sperm, which is in the crypts of the cervix all this time, still has a chance to penetrate the egg. It is therefore possible to get pregnant if you have unprotected sex during menstruation - whenovulation occurs quite soon after the end of the period, the sperm can still live and fertilize the female gamete. A certain number of healthy, motile male reproductive cells can also contain pre-ejaculate - a fluid produced by the male reproductive system during sexual stimulation but before ejaculation. Sperm are present in it spontaneously or come from semen remaining in the urethra after the last sexual intercourse. The conclusion is that during interrupted intercourse, pre-ejaculate can enter the uterus and lead to fertilization.

Sperm – Olympians, knights

It is worth noting that although sperm do indeed move quickly, they do not swim like Olympians, despite the fact that this comparison is very popular in the media. Firstly, the process of human fertilization is more of a giant lottery, not a sprint competition for sperm. Secondly, male gametes do not swim completely straight , but rather move in a slalom, which means that the actual distance they cover is longer. Therefore, out of 250 or even 500 million sperm produced during ejaculation (for comparison, the European Union has 447 million inhabitants), only a few hundred reach the fallopian tube. There, they undergo another selection – the process of capacitation, or preparation for fertilization. Only after this do several dozen male gametes reach the egg cell (usually located in the ampulla of the fallopian tube, i.e. its widest and longest part), whose lifespan from the moment of release during ovulation is from 12 to 24 hours. The male reproductive cells weaken its shell during the siege, which lasts about 3 hours. And as it happens in knightly skirmishes, only one of the battling sperms will manage to get into the fortress, i.e. penetrate the female gamete and consequently lead to fertilization.

Stop. I got carried away and started fantasizing like a real macho. As I know, at least from a great article by British biological anthropologist Robert D. Martin, it is a cultural, patriarchal stereotype that sperm are superactive and the egg is a passive participant in fertilization. This is the third myth, in addition to the aforementioned direct swimming of sperm and their competitive spirit. As RD Martin explains, sperm do not swim competitively through the entire female reproductive system, but rather are passively transported through part or all of this path by contractions and pumping movements in the uterus and fallopian tubes . This fact, like the importance of cervical mucus, indicates that the reproductive role of the body of people with uteruses is not as passive as is unfortunately often assumed.

How long do sperm live outside the body?

When I wrote at the beginning of the article about urban legends about sperm, I had in mind, for example, those that were printed in the once-hit magazine "Bravo". Who remembers the "Difficult Questions" corner? Readers sent questions to the editors, such as whether they could get pregnant if they dried themselves with their boyfriend's towel after a bath or if they used the toilet after him, because there could be sperm on the toilet seat. Supposed experts answered superficially that it was rather impossible, but the doubt, additionally fueled by cheap emotions, was sown in the minds of reading youth anyway.

Some of us remember "Bravo" with a nostalgic tear in our eyes, but it's good that it's a relic of the past. Many young people looked for information about sex there, although in the end they got access to entertainment, not actual knowledge. And what about the viability of sperm outside the body? In favorable conditions, i.e. high humidity and a temperature of about 37 degrees Celsius, the lifespan of sperm outside the body is from 15 to 18 hours . So it all depends on where the sperm lands after ejaculation.

In a bathtub filled with warm, not hot, water, sperm could survive for quite a long time. However, as we remember, they are not Olympians and traveling the path of the female reproductive system extended by a certain section of a water bath would be a crazy challenge for them, most likely ending in failure.

Neither a toilet seat nor a towel or a sheet provide favorable conditions for sperm. Male gametes dry out and die very quickly in the air, within a few minutes. And sperm on a finger? Some people fear that pregnancy can occur during caresses without penetration. However, sperm on a finger die about as quickly as sperm on sheets, so unless we are talking about direct insertion of semen into the vagina with a finger, the chance of pregnancy is zero.

There is a possibility of fertilization during anal sex, but these are extremely rare cases. There is no connection between the rectum and the vagina, although a rectovaginal fistula may develop as a result of infection or perinatal complications. In both cases, there is a possibility that the semen will leak from the rectum towards the moist vaginal opening and, through the already known route, will reach the egg. The chances of this are, as I mentioned, very small, but to be able to fully control the situation, use protection. A condom during anal sex is recommended not only to avoid unplanned pregnancy, but primarily to prevent inflammation of the male urethra from feces.

Lifestyle and sperm quality

The last myth I would like to address today is the claim that men remain fully fertile indefinitely. As I have already written, the process of spermatogenesis can last until old age, but with age – most often after the age of 50 – sperm motility and quality deteriorate . In addition, the risk of genetic diseases in the fetus increases . An inappropriate diet or weight, stress, sexually transmitted infections, smoking, exposure of the scrotum to heat – all of these and many other factors can negatively affect sperm production. For this reason, taking care of fertility means having it checked by a doctor and, above all, accepting the message that haunts us today, although it is true: lead a healthy lifestyle.