What Is Sperm?

A Technical Explanation

When your body works, it works. And it’s not until you get injured that you appreciate just how well the pieces work together. And for a few days, you’ll feel grateful to be fully healthy, until you go back to not thinking about it at all.

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When was the last time you thought about your sperm? For most men, the answer is effectively never, and that’s entirely normal. But understanding how sperm works is important, not just as a marker of your overall health, but also because most men want to preserve the option to have children in the future – and the option to freeze your youngest, healthiest sperm has become an increasingly common one. 

The goal of this guide is to provide a more technical explanation of what exactly sperm is, how it works, and how the sperm freezing process works. It’s ideal for those of you who want to understand, at a technical level, how everything works.

 

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What is it?

In the simplest of terms, sperm is the male sex cell – the male “gamete” – which combines with the female gamete in a process known as fertilization. Sperm cells are haploid, which means they carry half the amount of chromosomes that typical somatic (non-sex) cells do. A refresher from biology class – chromosomes are made up of DNA, which carries our genetic information. Thus, when a sperm cell combines with the egg, which is also haploid, they join chromosomes, making a diploid organism with 46 chromosomes. This is why you inherit some traits from your father and some from your mother. Sperm have 2 distinct parts: the head, which contains the nucleus where genetic material is carried, and a tail, which propels it for swimming and helps breach the egg.

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Time of the fertilization

Conditions are hostile from the very beginning – the acidic environment of the vagina will eliminate any sperm that linger for too long. Once they reach the cervix, they must navigate through an intricate web of mucus that can trap many. A great deal of sperm are then lost to crypts, side-channels where they can survive for several days. Once they reach the Fallopian tubes, many are bound to its surface, and only a select few are freed and continue on to the egg. It is believed that this long, arduous journey is nature’s way of weeding out the weak, so only the healthiest, strongest sperm survive.

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Does it divide or reproduce?

Sperm cannot divide or reproduce on its own, as well as have a limited life span. This makes fertilization a race to the top, from the vagina to the fallopian tubes, where they meet the egg and fertilization occurs. On average, anywhere between 80 and 300 million of them are released per ejaculation, after which they navigate a complex obstacle course to reach their final resting place. However, most are eliminated along the way; any abnormal or otherwise defective sperm fall to the many dangers of the journey, along with a good chunk of healthy sperm. In fact, less than 1 in a million from the original ejaculate will reach the egg at the time of fertilization.

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How do you determine the quality?

Sperm quality is determined through 3 main parameters: quantity, motility, and morphology. For one, you are more likely to be fertile if your ejaculate contains at least 15 million sperm per milliliter. Motility refers to a sperm’s movement and is of crucial importance to overcome the dangerous journey to the egg. You are more likely to be fertile if at least 40% of your sperm is motile. Morphology means the sperm’s structure – normally, smooth oval heads and long tails. Defects in morphology reduce the likelihood of being fertile. Specialists look at sperm holistically; just like with your overall health, doctors will put all the pieces together before coming up with a diagnosis. This is why Legacy doesn't limit its analysis to just count and concentration, but looks at additional factors like motility and morphology, both of which are important data points to understand your overall sperm health.

 
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When and where is it produced?

Sperm production does not begin until puberty, usually around ages 11-12. Once puberty begins, a whole host of physical and mental changes occur, among them the process of spermatogenesis, the development of mature sperm in the testis. Once sperm production starts, it will typically continue uninterrupted until death. Nonetheless, discernible defects in quality, quantity and motility increase with age. The whole process of spermatogenesis, from newly formed sperm to a fully mature one, usually takes around 74 days.  

 The testis produce around 50-100 million viable sperm daily. More specifically, they are produced in vessels within the testis called seminiferous tubules, and move to the epididymis and vas deferens for maturation.  Cool temperatures favor spermatogenesis, which is why during puberty the testicles descend from our body and start to hang between our legs. This keeps them about 4 degrees Farenheit below the usual body temperature of 98.6 Farenheit. Since sperm is constantly being produced in the testis, if there is no ejaculation after a period of time, the sperm are reabsorbed into the body.