What is semen?
Semen is a whitish fluid that is expelled from the urethra (tube inside the penis that also carries urine) in the ejaculate. The ejaculate is the product of the mixture of secretions from the testicle, where the sperm are produced, with the secretions of the prostate, seminal vesicles and bulbourethral glands. Normally every cubic centimeter of semen contains millions of sperm (sperm), but most of the volume is due to the secretions of the glands of the male reproductive organs (prostate and seminal vesicles, fundamentally).
The purpose of semen is merely a reproduction since it acts as a “vehicle” to transport sperm to the female reproductive tract. Although semen ejaculation accompanies orgasm and sexual pleasure, erection and orgasm are controlled by independent mechanisms, so the emission of semen is not essential for the enjoyment of sex.
Where is the semen made?
Semen is composed of the secretions of several glands but only 5% comes from the testicles
Testicles and epididymides
The sperm develops inside the testes from a cell called spermatogonium (called the primitive germ cell). Spermatogonia is divided to produce spermatocytes, which are then transformed into spermatids. The spermatid develops its tail and the cell gradually acquires the ability to move by shaking it. The spermatid eventually evolves into a mature sperm. This process takes about 60 days and the sperm takes another 10 to 14 days to pass through the ducts of each testicle and the sperm maturing tube, the epididymis, before being able to go outside in the semen, during ejaculation.
The fluid produced by the testicles also contains some substances, but it is especially rich in testosterone.
The seminal vesicles normally contribute more than half the seminal volume. Its secretions are especially rich in a sugar called fructose, which is an essential nutrient for sperm. They also produce a substance that causes the semen to coagulate (be sticky or gelatinous) after ejaculation and, in addition, appears to be useful in reproduction by keeping semen in the woman’s cervix.
The secretions of the prostate contain several chemicals, of which probably the most interesting is the prostate-specific antigen (PSA). PSA is an enzyme (a catalyst that promotes a greater speed of biochemical reactions) of a type called coagulase. The primary function of the PSA is to liquefy the coagulated semen so that the sperm can escape from it and progress to fertilize the egg in the reproductive tract of the woman.
The cells of the prostate produce PSA, and a part passes to the bloodstream, besides appearing in the semen. The larger and more active the prostate is, the more PSA will appear in the blood. Men with large benign (non-cancerous) prostates usually have higher blood PSA levels than the average. Men with prostate cancer can have very high levels. However, PSA levels may also be normal in both conditions. It is a useful marker for the size and activity of the prostate, although it is not a determinant test for prostate cancer.
Bulbourethral and urethral glands
The secretions of these glands lubricate the male reproductive tract.
What is normal semen?
The World Health Organization (WHO, 1999) provides a definition of “normal” sperm count, although it has changed over the years to the present:
About the concentration in the semen of the main substances, citric acid and fructose reflect the secretory capacity of the prostate and the seminal vesicles. Normal levels of both substances in ejaculated semen should be greater than 52 and 13 micromoles, respectively.
The amount of dead and abnormal sperm found in a “normal” sample is quite surprising.
The norms for an adequate collection of the semen for an analysis to evaluate its characteristics and potential fertility (the collection to evaluate the result of a vasectomy is simpler, in this case, it is enough to know if there are sperm in the sample and it does not matter other parameters) could be summarized in:
The measurement of the sperm count is a very technical issue and the results can be affected by many factors, including the time between ejaculation and the analysis of the semen sample or how the sample is stored when transported to the laboratory.
It is important to keep in mind that there may be a large variation in an individual’s sperm count, even within a few days. It is important that at least two and preferably three or more samples are analyzed, between which there is a period of two or three weeks apart. A single sample is not adequate to evaluate semen quality.
The sperm count is only an indication of the ability to fertilize and a normal count does not guarantee success. In addition, and paradoxically, the more quantity is not necessarily better, since too high a sperm count can result in fertility problems.
- Semen is usually white or grayish, but can sometimes appear yellowish. The pink or red semen suggests the presence of blood. Although this is only rarely due to a serious health problem, men with blood-stained semen should consult their doctor.
- The semen coagulates almost immediately after ejaculation forming a sticky and gelatinous liquid. It will liquefy again after 5 to 40 minutes. It is quite normal for semen to form gelatinous globules and this does not indicate any health or fertility problems. The difficulty in coagulating and then liquefying can cause fertility problems.
- The average volume of semen produced in the ejaculation is 2 to 5 ml. The volumes systematically less than 1.5 ml, (hypospermia) or greater than 5.5 ml. (hyperspermia) are probably abnormal. Lower volumes may occur after very frequent ejaculations and higher volumes are observed after prolonged abstinence.
Is male fertility declining?
Some experts suggest that the sperm count is in decline, others that there have been no changes. Even if the sperm count decreases, the effect on fertility is unclear. Currently, there is no clear evidence on any of these opinions. However, there are more articles that have suggested that the sperm count is decreasing and male fertility is declining.
Could environmental factors affect male fertility today?
Today there are many more environmental factors that can affect male fertility than 50 years ago. The factors include:
- Food factors Residues treated with clenbuterol or diethylstilbestrol Rapeseed or cotton oil Sweeteners (cyclamate) Dyes (orange II, hexachlorophene) Zinc deficiency, drastic hypocaloric diets.
- Toxic polluting agents (lead, cadmium, organophosphates, benzene hexachloride, chloropropane dibromo, DDT)
- Sexually transmitted infections
- Drugs (marijuana, cocaine, designer drugs, etc.)
- Use of anabolic steroids
- Ionizing radiation
- Working environments of excessive temperature
- Drugs (especially hormonal and cytotoxic products (agents that are used in chemotherapy, mainly)
- Exposure to certain toxic chemicals (pesticides, herbicides, heavy metals)
- Altitude (habitual residence at altitudes above 4,000 m).
How can I keep my fertility?
Some evidence suggests that stress reduces the quality of semen, probably due to the body’s hormonal changes resulting from stress. The causes of stress in modern life are innumerable and the concern about fertility or not being able to conceive are very important causes of stress. If you are concerned about whether you have a fertility problem, it is wise to ask your doctor for advice.
The chances of conceiving in a young and healthy couple are 20% per month, so a delay of three to six months before conception is not rare. It is reasonable to request an initial evaluation after six months of unprotected relationship in which it has not been conceived.
- Adopt a healthy lifestyle, with a balanced diet and regular exercise.
- Do not smoke or take drugs.
- Do not drink alcohol or keep consumption within the recommended limits.
- Try to avoid exposure to industrial and professional hazards, follow safety procedures and wear protective clothing when available.
- Avoid exposure to sexually transmitted diseases by adopting safe sexual practices.
Dr. John Dean, a specialist in Sexual Health.