What is spermatogenesis? Definition, periods

In the female and male body, the process of maturation of the sex cells is continuously proceeding. And if with the ladies everything in this respect is quite understandable, then men remain a mystery. It is unlikely that anyone far from medicine seriously thought about what spermatogenesis is. But to have a general idea would be good for broadening the general knowledge and a better understanding of one's own physiology.

Definition

To begin this improvised digression into biology and histology is better from the theoretical base. So, what is spermatogenesis? This is the process, the final product of which are spermatozoa. All stages of it are controlled by hormones and nervous system.

Each cycle lasts about ninety days. This is three times more than that of women, but the number of sex cells also rises several orders of magnitude more. In every hour of these 90 days in the testicles, a hundred million active spermatozoa mature. The most comfortable temperature for this process is 34-35 degrees Celsius.

Spermatogenesis can be conditionally divided into three phases, or a period:

- proliferation;
- meiosis;
- spermiogenesis.

Periods

What is spermatogenesis? It is a sequential process that has stages and stages. Biologists distinguish four types of changes in tissues:

- Reproduction of cells;
- growth;
- maturing;
- formation of ejaculate.

All this occurs in the seminiferous tubules located inside the testicles. The outer layer of cells forming the walls of the tubules is spermogonia. They are continuously dividing mitotically. This process begins before the birth of the child and lasts up to twenty-five years. Cells are divided so intensively that this period of time is called the period of reproduction.

After the onset of puberty, spermatogonia is divided into two groups:

- those that continue to share;
- those who move to the center of the tubule, into the growth zone.

At a new location, cells grow in size, they have a cytoplasm rich in nutrients. From spermatogonia they pass into spermatocytes of the first order. In this period of spermatogenesis, from each spermatocyte, two daughter cells are formed, and spermatids are already obtained from them.

Then the spermatids are evenly distributed along the testicle, lining it from the inside. And over time they gradually mature to spermatozoa, which fall into the vas deferens, and then into the urethra.

Proliferation

On the main membrane of the seminiferous tubules are located spermatogonia, the number of which at the time of puberty can reach a billion. According to their morphological features, they are divided:

- on light cells of type A;
- dark cells of type A;
- cells of type B.

Dark spermatogonia are reserve, they are in an inert state until the moment when they need (after a serious illness or radiation). Light cells continuously divide mitotically, creating both A- and B-type cells.

As a result of spermatogenesis in the embryonic period and from the moment of birth to 14 years, a significant pool of cells accumulating in spermatozoa accumulates in men. This provides them with a longer duration of fertility than for women (only 300 eggs, and they do not divide).

Meiosis: spermatogenesis

Spermatogonia, related to B-type cells, is first divided several times by mitosis and transformed into a first-order spermatocyte. This cell, in turn, is also divided, but not evenly, but meiosis. At the end of the first stage, two daughter cells are formed - spermatocytes of the second order, each of which contains a half set of chromosomes. The second stage is completed by obtaining two spermatids from each spermatocyte.

In total, four new cells are obtained from one. Each of them has a haploid set of chromosomes and in the future can participate in the fertilization of the egg.

Spermiogenesis

The difference between spermatogenesis and oogenesis is that in the finale there should be as many small cells containing genetic information as possible, not just one, but large and full of nutrients.

In order for a spermatozoon to form from a spermatozoon, it needs to undergo a series of serious morphological changes. Each spermatid is located next to the cage of Sertoli, where it "ripens". At first the cell is rounded, then stretched, and acrosomal granules appear in it. These inclusions are then collected at one of the poles of the cell, and there is an "acrosomal cap".

Mitochondria condense in the middle of the cell, they will move the sperm forward. The cytoplasm continues to stretch and the tail is formed. Once the cell has acquired its habitual appearance, maturation is over, and it takes its place on the inner surface of the spermatic cord.

Features of cell formation

What is spermatogenesis? Is a process whose main goal is the appearance of mature healthy germ cells possessing the necessary amount of genetic information. The entire process of the appearance of spermatozoa from basal cells takes a month.

In the male sex cells, specific enzymes are synthesized that help to detect the egg, get to it, dissolve the protective membrane and form a zygote. They are concentrated in the same arosomal cap, which has already been discussed above.

Another feature of spermatozoa is their mobility. The egg moves from the ovary to the fallopian tube and further into the uterus only due to the interaction with the pili, the translational motion of the cilia and the peristalsis of the tubes. Spermatozoon also has a tail, which plays the role of flagellum and pushes the rest of the cell forward.

The quality and viability of spermatozoa is influenced by the intake of drugs, alcohol, drugs and tobacco smoking, as well as other exogenous and endogenous factors.

Factors affecting the process

All sex cells and spermatogenesis are extremely sensitive to the effects of adverse factors. Violation of this process at some of its stages can lead to a decrease in fertility or infertility.

Despite the fact that the strong sex has all been accustomed to consider unshakable in terms of health, the male body is extremely sensitive to changes in body temperature and viral infections. It's enough banal cold with a slight hyperthermia to destroy plans for conceiving a child for three months.

Therefore, men should follow the basic recommendations for caring for their bodies in order to preserve the childbearing function for a long time:

- never wear tight underwear that can disrupt the blood flow and locally increase the temperature;
- avoid frequent visits to the sauna and bath;
- with caution take antibiotics, antiallergic and hormonal drugs.

Some women, worried that they can not conceive, try to work on the male body to improve the spermogram. To do this, you need to diversify food, give up bad habits, avoid frequent medications, drink herbal tea instead of coffee, exercise and periodically go to massage sessions.

Additional methods of influence on the body

Oogenesis and spermatogenesis can be strengthened artificially. For this, hormonal stimulation of partners is carried out in clinics of family medicine. As a rule, such procedures are done for couples who have decided to have a child under the IVF program (in vitro fertilization) or ICSI (intracellular sperm injection).

However, such procedures are not safe for both partners, and artificial stimulants inhibit the production of their own hormones and aggravate infertility. The natural activation of spermatogenesis occurs in men who are in love. The brain synthesizes many different hormones that improve not only the quality and quantity of seminal fluid, but also strengthen the immune system, increase muscle tone and accelerate metabolism.

Spermogram

In order to influence reproduction and spermatogenesis, it is necessary to conduct an analysis of the ejaculate. This detailed study allows you to determine the number of active spermatozoa, their quality, to identify pathological changes at an early stage (if any).

Normally, the ejaculate is a white or grayish liquid that has a neutral acidity. One milliliter should contain at least 20 million spermatozoa, and more than 25 percent of them must be mobile. In addition, the proportion of normal, fertile cells should be at least half of the total number. According to the standards of the World Health Organization, about fifty percent of spermatozoa should be alive and not have abnormalities in the morphological structure. In the seminal fluid, a slight presence of leukocytes and round cells is allowed. Erythrocytes, macrophages and amyloid bodies are not welcome.

There are such indicators spermogrammy:

- The normogram;
- oligospermia - a small amount of sperm;
- polyspermia - a lot of ejaculate;
- Viscosipathy - excessive viscosity;
- oligozoospermia - few spermatozoa;
- azoospermia - there are no spermatozoa in the liquid;
- astenozoospermia - immobility of morphologically unchanged spermatozoa.

There are other options, but these are the most common cases.