What is a spermatozoon? The structure, parts and functions. (2023)

a sperm, pluralsperm cell, or sperm is the male reproductive cell produced in the male testes by a process calledspermatogenesis.

The function of the spermatozoon is to enable sexual reproduction through union with the female egg during fertilization.

For this to happen, it is very important that the sperm cells keep their structure and DNA intact during their journey to the egg cell.

Definition and function

The spermatozoon is the male gamete destined to fertilize the ovum. It is the reproductive cell provided by the man to form an embryo which will later implant in the mother's womb causing pregnancy.

For this to be possible, both the male and female gametes must contain half the genetic material of the other cells in the body. Therefore, the sperm is known as athe haploid. Haploid cells have half as many chromosomes (one from each pair), and in humans there are 23 chromosomes.

This reduction in genetic material is achieved through the processdecrease. This takes place in the testis during sperm formation.

After the egg is fertilized by the sperm and their nuclei fuse, the genetic complement is restored. The fertilized egg now has 46 chromosomes. The resulting cell is now calledzygoot.

As we said before, the function of spermatozoa is sexual reproduction. For this to happen, sexual intercourse between a male and female is necessary for their gametes to come into contact with each other.

The male sperm is suspended in semen, which is expelled into the female reproductive tract by ejaculation. From here, the sperm will use its movement to travel through the fallopian tubes to meet the egg.

Another function of sperm is to determine the sex of the future baby. Depending on the chromosomal division that takes place during meiosis, the spermatozoon will have an X chromosome (female sex) or a Y chromosome (male sex).

Structure of human sperm

In 1677, the scientist Antonie van Leeuwenhoek was the first to describe the structure of a sperm cell in detail. They are elongated cells with a head, neck and tail, about 50 - 60 microns in length.

Sperm shape is similar in most species, especially mammals, although there may be minor differences.

The strangest thing about sperm is that it is the only human cell with a flagellum, the tail that allows it to move.

Next we will describe each of its parts:

Head

The head is an oval-shaped structure whose size varies from 5 to 8 µm. It consists of two parts:

acrosoom

It accounts for 40% to 70% of the total surface area of ​​the sperm head and is located at one end of the sperm. It contains proteolytic enzymes that help destroy the outer layer of the egg, making it easy for sperm to enter.

center

It contains the sperm's 23 chromosomes, which is half of the genetic information of the future embryo. This is the only part of the sperm that enters the egg. Therefore, it is the most important part of the semen. The goal is to fuse with the core of the egg and complete the genetic complement of the new creature.

plasma membranes

It surrounds the chromosome and nucleus to separate them from the rest of the sperm body. Inside is a small amount of cytoplasm with a high content of polyunsaturated fatty acids.

Neck and centerpiece

The neck and midsection are, as the name suggests, the parts between the head and tail. They are between 6 and 12 micrometers in size, slightly larger than the head. The width is barely visible under the microscope.

Within this segment there are millionsmitochondria. Mitochondria provide the sperm with the energy the tail needs to swim through the female reproductive tract.

Cola

The tail, also known aswhip, is a long structure that allows the main functionsperm motility. It does this with a gliding movement, similar to that of a snake.

The length of the tail is about 50 µm, which allows it to swim at a speed of about 3 millimeters per minute. Any defect in the sperm tail that affects motility leads to male fertility problems,

Once the sperm reaches the egg and the nucleus enters the egg, the tail is discarded.

Seed diseases and defects

There are several changes that can occur in sperm that can naturally prevent fertilization. Below we discuss the most common abnormalities that cause male infertility:

oligozoespermia

Low concentration of semen in the semen.

Asthenozoospermie

changes in spermatozoa motility due to defects that block or prevent the progression of the spermatozoa.

teratozoespermia

when the spermatozoa have poor morphology, head, neck or tail.

DNA fragmentation

The genetic material in the nucleus is broken or damaged.

The consequence of all these changes of the spermatozoa is their inability to travel to the ovum in the fallopian tube. If the sperm reaches the egg, these defects can mean problems with fertilization.

The changes in sperm structure that lead to this state of infertility are usually the result of production errors in the testicles. Likewise, changes can also occur during the maturation of the spermatozoa and their route to their expulsion in the ejaculate.

Depending on the severity of the male factor, the couple wishing to conceive may need to consider resorting to thisassisted reproduction techniques.

User FAQs

Which environmental parameters have the most influence on sperm quality?

By Marita Espejo Catena M.D., M.Sc., Ph.D. (gynaecologist).

One of the distinct features in sex cell production between males and females is that while females are born with a certain number of cells that become depleted over the years, males produce sperm every day from puberty onwards. This, along with the fact that the male reproductive organs are located outside the pelvis, determines the factors that can affect the quality of a sperm sample.

On the one hand, the location of the testicles outside the body means that their temperature is lower than the temperature of the rest of the body, and this reduction is a determining factor in spermatozoa production and motility.

The factors that can increase the temperature of the testicles, such as the presence of varicose veins at this level, obesity, the use of very tight underwear, a work activity that requires you to sit for a long time or even certain sports, such as cycling, will have a negative impact on the quality of the sperm.

On the other hand, there is the daily production of spermatozoa and this implies that external factors that can affect the man at a certain time will disrupt the maturation process of the spermatozoa at a certain stage. For this reason, a single semen examination is not sufficient to establish the diagnosis of male factor, as it must be confirmed with a second examination that will take one and a half to two months.

Exposure to environmental pollutants (including pesticides, fertilizers, solvents), consumption of toxins or even stress can have a negative effect on sperm quality.

How long do sperm cells live?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

The half-life of sperm is 2 to 5 days from the time they are ejaculated from the penis into the female reproductive tract. In the vagina and uterus they find the optimal conditions of humidity and temperature they need to survive. On the other hand, the spermatozoa ejaculated abroad quickly die within minutes.

In general, sperm cells are best able to fertilize within 24 to 48 hours after ejaculation.

When does sperm production start in men?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

A mother starts producing sperm and has her first ejaculations when puberty hits. This sperm production takes place practically throughout a man's life.

If you are interested in the changes that the male reproductive system undergoes during puberty and the development of sexual characteristics, we recommend that you read the following post:
Parts and functions of the male reproductive system

How far does a human sperm travel to fertilize an egg?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

The distance that spermatozoa travel through the female reproductive system is about 15 to 18 cm. The experts found that sperm must travel distances of about 1,000 times their own length while swimming in the right direction to the egg.

How fast can a sperm cell travel?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

Sperm with rapid progressive motility is type A sperm and can reach a speed of 25 micrometers per second. On the other hand, type B sperm cells have a speed of between 5 and 24 micrometers per second, while type C sperm cells have a speed of less than 5 micrometers per second. Finally, type D sperm are the ones that don't move.

For more information on this subject, please read here:analysis of sperm motility

Why does human sperm have many mitochondria?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

The mitochondria provide energy to the sperm and are responsible for carrying out the respiration process, which is necessary to provide the tail (flagella) with the necessary energy to allow the sperm to swim to the egg.

What is the function of the sperm head?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

The head is the most important part of the spermatozoon, as it contains the genetic material of the gamete in the nucleus. This genetic material, or DNA, is the male's identity marker, which must combine with that of the female to produce offspring for both members of the pair.

We could say that the sperm head serves as a reservoir for the male's DNA, and the transfer of this DNA is achieved thanks to the movement of the sperm tail.

What is the probability that a human sperm cell carries an X chromosome?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

Although there are many old stories and myths about it, the truth is that there is a 50% chance that a sperm cell carries an X chromosome and a 50% chance that it carries a Y chromosome. gender assignment is 100% random.

recommended reading

Here we discussed the anatomy of sperm. If you want to know more about how sperm is produced, you can find a lot of information in the following article:How is sperm produced?

In this article, we talked about the fertilization of the egg with the sperm. We recommend that you read more about the steps in this process in this post:What are the steps of fertilization?.