Male fertility: parts and functions of the male reproductive system

Male fertility is defined as the ability of men to cause pregnancy in women and subsequently have a baby. In this sense, and for a man to be able to conceive, it is necessary for his reproductive system to work properly.

In short, for a male to be considered fertile, the following processes are necessary:

  • The testes have to produce enough sperm in terms of quantity and quality in order to be able to fertilize the female’s egg cell.
  • Sperm ejaculation has to occur inside the vagina of the woman. This can only be achieved by having full sexual intercourse.

This system is connected and regulated by the sex hormones of males, which start working during puberty.

The various sections of this article are assembled in the following table of contents.

Structure of the male reproductive system

The male reproductive system consists of a set of internal and external organs depending on their location. What follows is a detailed classification of both parts:

External organs

The most important external genitalia of men are the penis and the testes or testicles, which are considered to be external sexual organs because they can be found outside the abdominal cavity.

Testes or testicles
These egg-shaped (hence the common name balls) organs are located inside a sack of skin called scrotum. Their main function is the production of sperm (spermatogenesis) inside the seminiferous tubules, as well as the production of testosterone.
Penis
It is the primary male sex organ used during copulation. Its main function is to place the semen inside the vagina of the female during intercourse. The penis is made of the corpus cavernosum, which is filled with blood to cause an erection, and the corpus spongiosum, which ends at the glans penis.

The testes are located externally because they have to be kept at a lower temperature than that of the body to promote sperm production. Alterations in the anatomy of the male reproductive system can lead to male infertility, as in the case of cryptorchidism.

Internal organs

The genitalia of the internal male reproductive organs can be found mainly within the pelvis. Their function is to release and transport the compounds that give raise to spermatozoa.

Epididymis
This tube is made of the whole set of seminiferous tubules, and is located behind each testis. It stores spermatozoa and creates the adequate atmosphere for their development.
Vasa deferentia or ductus deferens
It is a tube that transports sperm from the epididymis to the ejaculatory ducts.
Seminal vesicles
These glands are responsible for producing almost all the substances contained in the ejaculate. Moreover, they nourish and provide energy to the sperm that travel with it.
Prostate
It is a gland that segregates seminal fluid to protect the sperms. The bulbourethral glands or Cowper’s glands, which are responsible for releasing a lubricant fluid, are located under the prostate.
Urethra
Males use this conduct for both ejaculation and urination. It opens at the end of the penis.

Contrary to what happens in females, the urethra of males is part of both the excretory and the reproductive systems, as it is used for ejaculating and urinating interchangeably.

When do males start producing sperm?

Since they are born, boys have a different reproductive system from that of girls. Their reproductive organs, however, are not functional until they reach puberty.

When males turn 11-12 years of age, their endocrine system starts releasing male sex hormones (androgens), thereby beginning a period known as sexual maturity. It is at this point, which is called puberty, when they start producing sperm in the testes and developing the common male sexual characteristics:

  • Increase in height and muscle mass
  • Hair becomes larger and thicker
  • Appearance of facial hair
  • Deepening of the voice
  • Increase in body fat
  • Shoulders and chest become broader
  • First conscious ejaculations occur

It is from this moment on when a boy becomes fertile: he is now a teenager, which means that he has now the ability to cause pregnancy in women, that is, to have offspring.

During adulthood, it is actually very difficult to check if a man is fertile or not naturally. However, common signs of fertility in males include, but are not limited to, being free from stress, exercising regularly, not smoking, drinking alcohol or having toxic habits, using boxers instead of briefs, and being sexually active, among others.

Male fertility by age

In spite of the common belief that men can have children at any age, the truth is that a man’s age does matter. Although not as sharply as in females, the chances for a man to conceive decrease as he gets older.

Sperm quality starts decreasing after 40, and especially from age 50 onwards, which means that it might take longer for a man’s partner to get pregnant and, if it occurs, there exists an increased risk of miscarriage.

The following graph shows how a man’s age affects not only the chances of causing pregnancy in women, but also the likelihood of miscarriage, which at the same time decreases the live birth rates:

In short, between the ages of 30 and 50, the average man’s sperm quality declines by up to 30% in volume. Also, sperm motility is about 37% poorer, and morphology is five times more likely to be altered. This equals a greater potential for genetic abnormalities.

For couples undergoing IVF, the risk of failure is more than five times higher if the age of the male partner is equal to or greater than 41. In fact, statistics show that children with older fathers are more likely to have an autism spectrum disorder than those fathered by men aged 30 or younger.

Pathway of sperm

An essential aspect of male fertility is spermatogenesis, a process that takes place within the seminiferous tubules, that is, the structures that can be found within the testes.

Sperm production is a complicated process. It involves the successive division of spermatogonia, which are undifferentiated male germ cells. The entire process of spermatogenesis is estimated to take between 64 to 72 days.

Once produced, sperm are stored in the epididymis, where they acquire the appropriate motility. Then, they travel to the vasa deferentia, where they mix with the seminal fluid released by the accessory glands (seminal vesicles, prostate, and bulbourethral glands). Finally, the sperm produced reach the urethra and come out of the man’s body with ejaculation.

After intercourse, as long as ejaculation occurs, semen enters the vagina, and that is the moment when they start their journey toward the female reproductive tract thanks to their ability to swim and move forward. Only those able to meet the egg in the Fallopian tube have the chance to fertilize it and give raise to an embryo.

Any alteration in the male reproductive organs that prevent them from producing or transporting sperm, as well as hormonal imbalances, may lead to male sterility.

FAQs from users

What increases fertility in males?

Foods, vitamins, supplements, and other natural remedies said to improve fertility in males can work, yet not in the most severe cases. For instance, improving your diet, reducing chemical exposure, exercising regularly, and taking nutritional supplements and vitamins can help to some extent.

What affects fertility in males?

Cigarette smoking, alcohol drinking, street drug use, pollution, radiation, chemicals, drugs, heavy metal exposure, etc. can lead to low sperm count or poor sperm motility. Also, hot baths, tight-fitting underwear, sitting for long periods of time, working with computer laptops on the lap, and carrying cellphones in the front pocket are habits that damage the overall quality of sperm.

How can chemotherapy affect fertility in males?

Since chemotherapy works by killing cells that are dividing quickly, and sperm cells are included within this group, chemo affects them to a large extent. Permanent infertility can occur if all the spermatogonial sperm cells are affected to the point that they can no longer produce sperm. This risk is dependent on the patient’s age, the type of drug used, and the dose given.

What is the male reproductive organ that makes testosterone?

The testes or testicles are the organs responsible for making testosterone, which is the primary male sex hormone.

Does diabetes affect fertility in males?

Diabetes can cause male infertility in three ways:

  1. It affects the health of small blood vessels and lowers testosterone levels, which causes erectile dysfunction.
  2. Given that it lowers testosterone levels, it reduces the man’s libido.
  3. The combination of these three factors contributes to reducing the ejaculate volume.

Suggested for you

If you are interested in learning more about the sperm’s journey to the egg, we recommend you to read the following post, which includes pictures that will help you understand the process from beginning to end: How sperm meets egg with pictures.

On the other side of the coin, there exist different types of male infertility depending on what is causing it. We have created a comprehensive guide to male infertility so that you are able to understand it and consider your chances of starting a family in spite of sterility. Here you go: What causes male infertility?

2 comments

  1. usuario
    majorHUM

    Hello Sandra,

    I want to know if there is any way that could help us check if husband is infertile at home. We’ve been told recently that he’s got a blockage in his reproductive tract, and it’s why we’ve been unable to conceive despite having been ttc for 3 yrs and a half.

    Any advice pls?

    • avatar
      Sandra F.Fertility counselor

      Dear majorHUM,

      Obstructive azoospermia is the least severe type of azoospermia, as sperm production still takes place. The problem is that, in spite of being produced, they cannot come out of the man’s body due to the blockage present in the ejaculatory ducts, which can be caused by infections, inflammations, retrograde ejaculation, etc. The most appropriate treatment in this case involves surgery for the removal of the blockage. Also, a testicular biopsy could help you retrieve sperm from the testes and fertilize them with your egg cells in the laboratory by means of in vitro fertilization (IVF).

      See also: What is obstructive azoospermia?

      I hope this helps,

      Best wishes