By Cristina Mestre Ferrer BSc, MSc (embryologist).
Last Update: 02/24/2015

The number of spermatozoids released during ejaculation, varies greatly among men and also within the same man. It depends on the duration of abstinence, on fatigue and on the general health of the man.

No two men are the same; each one is different so it is not strange to think that their ejaculations are also different.

There are not only variations between men, but also within the same man, since there might be differences in his ejaculations depending on the pleasure experienced during sex, the level of fatigue, how long he has been keeping abstinence, etc.

Spermatozoids expelled during ejaculation

Many men wonder if their semen is too thick, or, on the other hand, if it is too liquid . Generally, when expelled, semen has a thick consistency.

Alterations in the density of semen can difficult the process of conceiving a child. Extremely dense or highly viscous semen may be an indication of infertility.

The density of the spermatozoids in the semen varies from 50 to 150 million per millilitre, so that each ejaculation contains up to 400 million spermatozoids.

Ejaculation

Semen is thick at the moment of ejaculation, so it can be properly ejected and guarantee that a larger number of spermatozoids reach the vagina. It is important to remember that the ultimate goal of the spermatozoids is to fertilize the egg. All the spermatozoids have to travel a long way to reach the fallopian tubes, where it will meet the oocyte.

In order to assure that a higher number of spermatozoids reach the vagina, semen is expelled as clots. That’s the reason why its consistency is so dense. This happens due to a substance generated by the prostate called spermine phosphate and due to semenogelin proteins that are responsible for coagulation the sperm.

Other proteins called lysines are responsible for making sure that, once in the vagina, spermatozoids are able to ascend the female tract. The main function of these proteins is to liquefy the semen, approximately 10 minutes after it has been expelled, so that spermatozoids can move through the female reproductive tract.

Spermatozoid shape

If, during ejaculation, the semen was too liquid it would easily go outside the vagina and the process of conception would be more difficult to achieve.

During the moment of ejaculation between 80 and 400 million spermatozoids are expelled. Thousands of those spermatozoids run to the fallopian tubes, hundreds reach the egg but only one will be able to fertilize it. From that moment on, a protection mechanism, that prevents any other sperm from penetrating it, is activated in the oocyte membrane.

Semen composition

Semen is composed of a group of substances responsible for giving it a certain consistency and density, so a spermatozoid can fertilize the egg. Approximately 10% of its contents are spermatozoids and the seminal fluid confers roughly 90% of its consistency.

The substances that compose the seminal fluids are mainly produced by the seminal vesicle and prostate. The seminal vesicle contains between 40% and 60% of the volume of the semen and mainly liberates:

  • Fructose
  • Prostaglandins (E2, A, B)
  • Amino Acids
  • Phosphorus
  • Potassium
  • Hormones

The Prostate contains 15% to 30% of the seminal plasma. It mainly liberates:

  • Citric acid
  • Cholesterol
  • Phospholipids
  • Carnitine
  • Alkaline phosphates
  • Calcium, sodium, zinc and potassium

Urethral and Bulbourethral glands also contribute to the composition of the sperm. These glands contain the last element that is added to the semen, a clear, thick and lubricant protein that represents between 3 and 6% of the total sperm.

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Authors and contributors

 Cristina Mestre Ferrer
BSc, MSc
Embryologist
Bachelor's Degree in Biological Sciences, Genetics & Human Reproduction from the University of Valencia (UV). Master's Degree in Biotechnology of Human Assisted Reproduction from the UV and the Valencian Infertility Institute (IVI). Embryologist at IVI Barcelona. More information