Understanding Sperm: The Foundation of Human Reproduction

Oct 7

6 min read

Updated: 3 days ago

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026

Quick Answer: What are sperm?

Sperm are tadpole-shaped male sex cells, also called gametes or spermatozoa, that carry genetic material to an egg. [1] They are produced in the testicles starting at puberty. [1] A healthy sperm uses its tail to swim through the female reproductive tract, where it can survive for up to five days, and only one needs to penetrate an egg for conception. [1]

What the research says

WHO reference values show what “normal” semen looks like in fertile men. Using semen samples from more than 4,500 men in 14 countries, the lower reference limits (fifth percentile) in men whose partners conceived within 12 months were: sperm concentration 15 million per ml, total sperm number 39 million per ejaculate, progressive motility 32%, total motility 40%, vitality 58% live, and morphologically normal forms 4.0% (Cooper et al., Hum Reprod Update, 2010) [2].
Sperm counts fell sharply among unselected men in Western countries. A meta-regression of 185 studies (42,935 men, samples from 1973 to 2011) found that mean sperm concentration among unselected Western men declined by 52.4% and total sperm count by 59.3%. No significant trends were seen in the “Other” geographic group (South America, Asia and Africa), and the authors called for urgent research on causes (Levine et al., Hum Reprod Update, 2017) [3].

What is the structure and function of sperm cells?

Sperm cells are highly specialized biological units with a singular purpose: fertilization. Each cell is divided into three distinct anatomical regions that work in harmony to ensure the successful delivery of DNA to an ovum.

Part	Component	Primary Function
Head	DNA and acrosome	Contains genetic material and enzymes to penetrate the egg.
Midpiece	Mitochondria	Generates the energy required for movement.
Tail	Flagellum	Provides propulsion through a corkscrew-like motion.

The head of a healthy sperm is typically almond-shaped, allowing for efficient movement. The acrosome, a protective cap over the head, releases specific enzymes that break down the outer layer of the egg cell during contact. The midpiece acts as the “engine room,” housing mitochondria that supply the chemical energy needed for the tail to whip and drive the cell forward. [1]

Illustration of a sperm cell showing its head, midpiece, and tail, beside a diagram of the male reproductive tract with arrows tracing the path sperm take from the testicle. – rinnit.com — A sperm cell has a head, midpiece, and tail, and travels through the male reproductive tract during ejaculation.

How are sperm produced, and what is their lifecycle?

The production of sperm begins during puberty, typically between ages 10 and 12, and occurs within the seminiferous tubes of the testicles. [1] Unlike female egg cells, which are present from birth, sperm are produced continuously throughout a male’s life.

Once produced, sperm follow a specific pathway through the reproductive system. They exit the testicles and travel to the epididymis for maturation before moving through the vas deferens and prostate gland. (See our guide to the seminal vesicles for another part of this system.) During ejaculation, sperm enter the urethra and are released within a fluid called semen. [1] Sperm that are not ejaculated can stay alive in the testicles for about 2.5 months, after which they die and are reabsorbed by the body. [1]

What factors affect sperm health and fertility?

Sperm health is generally measured by three primary factors: count, morphology (shape), and motility (movement). Imbalances in these areas can lead to infertility or difficulty in achieving conception. [1]

Factor	Definition	Normal Range or Description
Count	Concentration of sperm in semen	15 million to 200+ million per milliliter.
Morphology	Physical shape and structure	Almond-shaped head with a single, straight tail.
Motility	Ability to swim effectively	Swimming strongly in a straight line.

Several conditions and lifestyle factors can negatively impact these metrics. For instance, varicoceles, which are swollen veins in the scrotum, can increase internal temperatures and hinder sperm growth. [1] Some sexually transmitted infections, including chlamydia and gonorrhea, can also harm sperm. [1] Environmental factors such as smoking, alcohol consumption, and prolonged exposure to high heat (such as in saunas or hot tubs) are known to reduce sperm quality. Testosterone replacement therapy also causes the body to stop producing sperm (read more about low testosterone). [1]

Illustration comparing a normal sperm with acephalic, double-headed, and coiled-tail sperm on the left, and on the right the effect of heat exposure from a sauna and of smoking on sperm. – rinnit.com — Abnormal sperm shapes, heat exposure, and smoking can all affect sperm health.

What are common sperm disorders and how are they tested?

When fertility issues arise, healthcare providers often perform a semen analysis to evaluate the health of the sperm. This test provides a comprehensive look at the quantity and quality of the cells released during ejaculation.

Recognized Sperm Disorders

Oligospermia: A low sperm count, defined as fewer than 15 million sperm per milliliter of semen. [1]
Azoospermia: The complete absence of sperm in the semen [1], often caused by a blockage in the reproductive tract.
Teratospermia: A high concentration of sperm with abnormal morphology [1], which can prevent successful fertilization.

In some men with no sperm in the ejaculate, sperm can be retrieved surgically (see our guide to microTESE) and used in intracytoplasmic sperm injection (ICSI).

How can you support healthy sperm and reproductive vitality?

Many aspects of sperm health can be supported through proactive lifestyle choices, even though some sperm conditions are genetic or medical. Protecting the testicles from trauma and maintaining a healthy internal environment are essential steps.

Illustration of four pillars around a central sperm icon: keeping the testicles cool (ice pack and thermometer), no smoking, protection against infections (a shield with a condom), and healthy foods such as fruit, vegetables, nuts, and fish. – rinnit.com — Four everyday pillars that support sperm health: staying cool, not smoking, protection against infections, and a healthy diet.

Health Care Pillars

Temperature regulation: Avoid prolonged exposure to high heat, as the testicles require a slightly lower temperature than the rest of the body for optimal sperm production.
Lifestyle modifications: Reducing or eliminating tobacco, alcohol, and marijuana use may improve sperm count and quality.
Regular screenings: Testing for and treating sexually transmitted infections (STIs) like chlamydia and gonorrhea can help protect sperm from harm.
Nutritional awareness: A balanced diet with plenty of fruits and vegetables, along with a healthy weight and regular physical activity, helps support sperm quality. [1]

Conclusion

Sperm cells are remarkable examples of biological engineering, designed for the high-stakes journey of fertilization. By understanding their structure, the factors that influence their health, and the importance of regular diagnostic testing, individuals can take informed steps toward protecting their reproductive future.

Next Steps

If you and your partner are experiencing difficulty with conception, or if you have concerns about your reproductive health, consult a healthcare professional for a comprehensive semen analysis. Early detection of sperm disorders can often lead to effective treatments and improved fertility outcomes.

Trusted resource: Cleveland Clinic: Sperm.

Frequently Asked Questions

What is the main function of a sperm cell?

A sperm cell's sole function is to travel to and fertilize a female egg cell to begin the process of reproduction.

How long does it take for the body to produce new sperm?

The entire production and maturation cycle takes approximately 2.5 months.

Can sperm survive outside the body?

At room temperature, sperm can live for up to an hour, though they are highly sensitive to temperature changes.

How long can sperm live inside the female reproductive tract?

Healthy sperm can remain viable and capable of fertilization for up to five days.

What is a “normal” sperm count?

A typical count ranges from 15 million to over 200 million sperm per milliliter of semen.

What does “morphology” mean in relation to sperm?

Morphology refers to the physical shape and size of the sperm, specifically the head, midpiece, and tail.

Does the body stop producing sperm at a certain age?

No, unlike women, men can continue to produce sperm throughout their entire lives.

What are varicoceles and how do they affect sperm?

Varicoceles are swollen veins in the scrotum that can raise the temperature, potentially damaging developing sperm.

Can medications affect sperm quality?

Yes, certain drugs for high blood pressure, heart failure, and prostate cancer can impact sperm health.

What is the difference between sperm and semen?

Sperm are the microscopic reproductive cells, while semen is the fluid that carries and protects them.

How does smoking affect male fertility?

Smoking and vaping can decrease both the count and the overall quality of sperm cells.

What is azoospermia?

Azoospermia is a condition where there is no sperm present in the ejaculated semen.

Can the immune system attack sperm?

Yes, in some cases, the immune system produces antisperm antibodies that mistakenly target and kill sperm cells.

What is the acrosome?

The acrosome is a cap-like structure on the sperm head that contains enzymes used to penetrate the egg’s outer layer.

How can I improve my sperm health?

Maintaining a healthy weight, avoiding excessive heat, and quitting smoking are among the most effective ways to support sperm quality.

References

Cleveland Clinic. Sperm. Cleveland Clinic. July 25, 2024. https://my.clevelandclinic.org/health/body/sperm
Cooper TG, Noonan E, von Eckardstein S, et al. World Health Organization reference values for human semen characteristics. Hum Reprod Update. 2010;16(3):231-245. PMID 19934213. https://doi.org/10.1093/humupd/dmp048
Levine H, Jørgensen N, Martino-Andrade A, et al. Temporal trends in sperm count: a systematic review and meta-regression analysis. Hum Reprod Update. 2017;23(6):646-659. PMID 28981654. https://doi.org/10.1093/humupd/dmx022

Medical Disclaimer

This article is for informational purposes only and does not constitute medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read in this article.