Facts About Sperm You May Not know (2024)

Sperm are the reproductive cells produced by the testicl*s (testes) that carry the male partner's genetic material (chromosomes).

During vagin*l sexual intercourse, sperm are ejacul*ted from the penis into the vagin*. They can migrate to the uterus and fallopian tubes, where they can fertilize the egg, which carries the chromosomes of the female partner. If conception occurs, the combined genetic material will influence the baby's traits.

Every day, around 100 to 200 millionsperm cells are produced by the testes. The process by which sperm cells are produced, called spermatogenesis, takes around 74 days.

This article explains what sperm are, including their types and composition, their role in reproduction, and how many sperm cells are needed to achieve pregnancy. It also explores ways to improve sperm counts if you are faced with infertility.

Sperm Composition and Production

Sperm cells, also known as spermatozoa, serve one purpose in the human body: to fertilize the egg (ovum).

Each sperm cell is comprised of three parts:

• A head, which contains enzymes that help it penetrate the outer membrane of the egg
• A neck, which contains cells called mitochondria that power the cell
• A tail (flagellum), which creates wave-like movements to propel the cell toward the egg

Each sperm cell carries 23 chromosomes that provide the father's genetic information. When fertilization occurs, these chromosomes combine with 23 chromosomes from the egg, creating a fused cell with 46 chromosomes called a zygote.

Among the 23 chromosomes that each parent contributes, one will be a sex chromosome. Sperm carry an X or a Y chromosome, while the egg carries an X chromosome. If an XX pairing is typical for a biologically female offspring, then an XY pairing is typical for a biologically male offspring.

Spermatogenesis and Life Cycle of Sperm

Spermatogenesis is the biological process responsible for the production of sperm that takes around 74 days from start to finish. It starts when the pituitary gland secretes two hormones (chemical messengers) that act on the testicl*s in different ways:

• Follicle-stimulating hormone (FSH) causes immature germ cells inside the tubes of the testicl*s to divide and multiply, eventually yielding four spermatozoa per germ cell.
• Luteinizing hormone (LH) stimulates cells in the testicl*s (called Leydig cells) to produce testosterone, which aids sperm maturation.

Once the immature sperm cells have tails, they move from the testes into a coiled tube (called the epididymis), where they will continue to mature for the next five weeks.

Once maturation is complete, the cells move into the vas deferens (sperm duct), where they mix with a liquid called seminal fluid to create sem*n. These fluids, produced by the prostate gland and seminal vesicles, help nourish sperm and propel them out of the body during ejacul*tion.

Around 300 million sperm are ejected with each ejacul*tion. This many are needed because only around 1 million make it into the fallopian tube, where the egg starts its descent toward the uterus (womb). Of those that reach the egg, only a few hundred are viable for fertilization.

If sperm are not ejacul*ted within their 74-day life cycle, the majority will die and be reabsorbed by the body. Others will be passed out of the body in urine.

Sperm Count Across a Male Lifetime

Sperm cells are produced continually, starting from the onset of puberty right through old age. Although fertility in females terminates with the onset of menopause, a male can continue to produce sperm for the rest of their life. In rare cases, some have been known to induce pregnancy well into their 90s.

Studies vary, but over the course of a lifetime, a male can produce close to a trillion sperm cells. Even so, the ability to achieve conception can start to decline even if sperm counts remain relatively steady.

For most, the decline in fertility will start around age 40 when sperm cells become less viable due to the accumulation of free radicals (unstable molecules produced by cell metabolism). The ensuing DNA damage can affect both the morphology (structure) of the sperm cells and their motility (movement).

In most males, the decline in sperm motility and morphology tends to be slow and steady, decreasing by 1% to 2% per year from age 40.

Sperm Count for Conception and Pregnancy

Infertility is defined as the inability to conceive despite having vagin*l sexual intercourse for at least one year. Around half of all cases are the result of male infertility, of which 90% involve sperm abnormalities.

A sperm count, also known as a sem*n analysis, provides valuable information about problems that can lead to infertility. The test counts the number of sperm in your sem*n and also evaluates their shape and movement along with the acidity, volume, and appearance of sem*n.

Because sperm counts can fluctuate day by day, the testing will typically involve two or three samples taken at least seven days apart. The average of the results offers better insights than a single test.

The results of a sperm analysis are generally interpreted as follows:

• Sperm count: A count of 20 million to over 200 million is generally considered normal.
• Sperm morphology: A result is considered normal if more than 50% of the sperm cells in a sample are normally shaped.
• Sperm motility: This is scored on a scale of 0 to 4 based on how quickly sperm move one hour after ejacul*tion. For a normal result, over 50% of the sperm must be motile. A score of 0 means that the sperm are not moving, while a score of 3 or 4 represents good movement.
• sem*n pH: This test measures how acidic or basic your sem*n is. A pH between 7.2 and 7.8 is considered normal.
• sem*n volume: A person should ideally produce at least 2 milliliters of sem*n (roughly half a teaspoon) per ejacul*tion. Anything less (known as hypospermia) reduces the odds of fertility.
• sem*n liquefication: sem*n should liquify within 15 to 30 seconds after exposure to air. Anything slower can impede the movement of sperm and make conception more difficult.
• sem*n appearance: sem*n should be pearly white, cream, or gray. Red or brownish sem*n may be a sign of bleeding, while yellow or greenish sem*n may be a sign of infection.

Sperm Life After Unprotected Sex

The duration of sperm survival can make a difference between your ability to conceive and not conceive.

Under the right circ*mstances, sperm can remain viable in the female reproductive tract for up to five days, although the percentage of viable sperm will decline rapidly over time. Some older studies suggest that by Day 4, only around 5% of sperm will have survived.

However, some factors can increase or decrease survival times, including:

• vagin*l pH: Sperm thrive in an alkaline environment and can die within hours in an acidic one. The window during which cervical mucus turns alkaline lasts only a few days with the onset of ovulation. Sex before or after this window can reduce sperm survival times.
• Seminal pH: Highly acidic seminal fluid can also affect sperm survival. Acidity can increase if the seminal vesicles become blocked, causing acidic fluids from the prostate gland to overtake alkaline ones from the seminal vesicles.
• Scrotal temperature: Sperm survival requires a lower temperature than that of the body. Overheating the testicl*s beyond 96 degrees reduces survival by damaging the energy organelles of the sperm, called mitochondria.

What Changes Sperm Count?

Many things can lower your sperm count. Some of these factors are modifiable (meaning you can change them), while others are non-modifiable (meaning that you can't).

Certain factors can also increase your sperm count.

Lower Sperm

Oligozoospermia can sometimes be idiopathic (meaning of unknown origin). More often than not, the cause is known and diagnosed during testing.

Non-modifiable risk factors for low sperm counts include:

• Varicocele: The highly treatable enlargement of the veins inside the scrotum
• Cryptorchidism: Also known as an undescended testicl*
• Testicular trauma: Including injuries, testicular surgery, and testicular radiation
• Genital infections: Including infection of the epididymis (epididymitis) or testicl*s (orchitis)
• Sexually transmitted infections (STIs): Particularly untreated gonorrhea or chlamydia
• Retrograde ejacul*tion: The backflow of sem*n to the bladder rather than out of the penis
• Pituitary tumors: Including benign adenomas that can reduce the production of FSH and LH
• Antisperm antibodies (ASA): An autoimmune condition that targets and destroys sperm cells
• Klinefelter syndrome: A genetic disorder in males caused by an extra X chromosome
• Kallmann syndrome: A genetic disorder that causes delayed sexual development
• Toxic exposures: Including benzene, herbicides, organic solvents, or heavy metals like lead

Modifiable risk factors for low sperm count include:

• Heavy alcohol use: Sperm count can be reduced with as few as five drinks per week.
• Anabolic steroids: Can cause testicular shrinkage and reduced sperm production
• Depression and anxiety: Trigger an increase in cortisol, a stress hormone, and an associative drop in testosterone
• Excessive exercise: Increases cortisol levels, bringing down testosterone levels
• Sleep deprivation: Has the same effect on the body as stress and excessive exercise
• Smoking: Reduces blood flow to the testicl*s along with sperm production
• Obesity: Triggers the production of an enzyme called aromatase that reduces testosterone
• Overheating the testicl*s: Including wearing tight jeans or briefs or occupations that require prolonged sitting (like truck driving)

Higher Sperm

Generally speaking, having a high sperm count (over 300 million per milliliter) is neither a problem nor a medical concern. It may be that you have a naturally high sperm count, or it may be an incidental increase caused by a long gap between ejacul*tions.

A high sperm count should not be confused with hyperspermia. Hyperspermia is a condition in which you produce large amounts of sem*n, generally above 7 milliliters (or 1.5 teaspoons).

Hyperspermia poses no health risks, although it may be a sign of a male genital tract infection (particularly if it is accompanied by testicular pain, swelling, and fever).

The only other concern is that hyperspermia can dilute the relative volume of sperm in your sem*n, leading to a loss of fertility no more or less severe than hypospermia (low sem*n volume).

Sperm Fertility Assistance

Male infertility related to sperm may be due to oligozoospermia (a low sperm count), teratozoospermia (abnormal sperm), asthenozoospermia (abnormal sperm motility), or azoospermia (a total absence of sperm).

The treatment of these and other sperm abnormalities may require the care of a urologist (who specializes in male infertility) or a reproductive endocrinologist (who specializes in hormonal disorders affecting fertility).

Depending on the cause, the healthcare provider may recommend:

• Antibiotics: Used to treat bacterial genital tract infections, including STIs
• Testosterone replacement therapy (TRT): Delivered orally, topically, or by injection to treat low testosterone
• Gonadotropin therapy: Using injections of FSH or LH to stimulate the production of sperm cells
• Immunosuppressants: Using drugs like prednisone and cyclosporine to dampen the effects of ASA
• Surgery: Used to correct varicoceles, cryptorchidism, and pituitary adenoma
• Assisted reproduction therapy (ART): Involving the collection of sperm from ejacul*tion, surgery, or donors to use for in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI)
  

Summary

Sperm are male reproductive cells whose sole function is to fertilize eggs. Sperms cells are produced by the testicl*s, the production of which is regulated by the pituitary gland. The life cycle of sperm is roughly 74 days.

Between 100 and 200 million sperm cells are produced each day, with around 300 million released during each ejacul*tion. Roughly 1 trillion sperm cells are produced over the course of a lifetime.

A low sperm count is when there arefewer than 15 million sperm per milliliter of sem*n or fewer than 39 million sperm per ejacul*tion. Many conditions affect sperm count, quality, and motility. A sperm analysis is the first step in diagnosing the cause of male infertility and dispensing the appropriate treatment.