Men can be just as curious as women. Therefore, some of them are very interested in the structure of their own body, and especially its most important organs. The brave in this case become doctors, and the rest simply read the necessary literature. The most important questions remain: Where is the spermatozoon formed? What does he look like? How many lives? And how is it moving? Let's try to answer them in a way that everyone can understand.
Definition
Before answering the question of where a sperm cell is formed, you need to understand what it is. Spermatozoa are the sex cells of animals and humans. As a rule, these cells are able to actively move, which is vital in order to reach the egg and fertilize it.
Compared to the female sex cell, spermatozoa are small, brisk, and a large number of them mature in the body at the same time (unlike the egg, which alone is the crown of the thirty-day work of the woman's endocrine system).
The structure of this sex cell indicates that all animals and fungi hadthe common ancestor is a unicellular organism. Traditionally, any male reproductive cells, even in plants, are called spermatozoa, although the definition of “sperm” is also applicable to them, as well as anterozoids.
Spermatozoa in animals
Oddly enough, but animals do not differ much from humans in terms of the structure and function of germ cells. Where are spermatozoa formed? How do they look? Are there any fundamental changes?
A normal animal spermatozoon has a head, an intermediate part and a tail (or flagellum). In the head, traditionally, the nucleus is located, in which there is a half set of chromosomes. In addition to genetic information, the head contains enzymes for introduction into the egg and centriole. In the intermediate part, it is also the neck, there is a large mitochondrion, which provides energy to the flagellum and maintains its movement.
Exceptions to the above sample are some types of aquarium fish, whose spermatozoa have two flagella. This also applies to crustaceans (they may have three or more "tails" in germ cells). But evolution offended roundworms by mobile cells - there is not a single cilium or flagellum in its entire body. The germ cells of these animals have a plastic cell wall, which allows them to move with the help of pseudopods. Newts have a fin on the spermatozoon. But variations are not only in the tails, but also in the heads. If in humans they are ellipsoid, then mice and rats can boast a hook-like shape.
The size of germ cells in men is extremely small - from tens to hundreds of micrometers. This variation has nothing to do with the size of an adult.
Opening spermatozoa
Before scientists thought about the question "Where is the spermatozoon formed?", they had no idea that there are special cells involved in the reproduction of humans and animals. And in general, they had a very distant idea about the structure of living tissues.
A revolution in science took place in the middle of the seventeenth century, when the Dutchman Antoine Leeuwenhoek invented a microscope and began to examine various objects in it: pollen, leaves and petals of plants, human and animal skin, and much more. In 1677, it came to germ cells. He described the egg and sperm, which he called the "seed animal".
Like any scientist, Leeuwenhoek first did all the experiments on himself, so human spermatozoa were described first, and only then other animals. The idea that these "animals" are involved in conception quickly occurred to Antoine, which he did not fail to report to the British Scientific Society.
But this hypothesis was rejected, and for another hundred years spermatozoa were considered parasites in the male body, having nothing to do with fertilization. Only at the beginning of the nineteenth century, the Italian Spallanzani proved the veracity of this theory.
Building
If you do not take into account the length of the flagellum, then the sperm cell is the smallest cell in the human body, about55 micrometers. Such a small size allows him to quickly move into the uterine cavity and reach the egg.
In order to be even smaller, in the process of sperm formation, they undergo a series of transformations:
- the nucleus becomes denser due to the condensation of genetic material;
- the cytoplasm is separated into a separate cytoplasmic drop”;- only those organelles that are vital for the cell remain.
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The head of the spermatozoon has the shape of an ellipse, flattened laterally. Sometimes it can be concave on one side, and then we can talk about a spoon-shaped shape. In the head are:
- a nucleus with a haploid set of chromosomes. This is necessary so that after the fusion of two germ cells, the total amount of genetic information is equal to that in somatic cells, otherwise the fetus will not survive or will have deformities. Due to the strong “compression” of chromatin, it is in an inactive state and cannot synthesize RNA.
- The acrosome is an evolutionarily modified Golgi apparatus, it is necessary so that the sperm head can enter the egg. - centrosome - an organelle that supports the "skeleton of the cell" and ensures the movement of the tail.
- The midsection or neck is the narrowing between the head and tail. It houses the mitochondria, which generates energy for the movements of the flagellum.
- The tail or flagellum is the thin moving part of the spermatozoon. Performs rotational translational movements, allowing the cell to reach the goal.
Function
The way and place of formation of spermatozoa are closely related to its functions. And the most important of them is the penetration into the egg and fertilization. To perform this function, nature has provided mobility, mass and chemical "attractiveness" of spermatozoa.
Female and male organisms are designed to reproduce their own kind, so they are compatible physically, chemically and genetically. If a man takes care of his he alth, does not have bad habits, has done all the vaccinations on time (especially against mumps), then his germ cells will be ready to perform their function at any moment.
Movement
The formation of spermatozoa in men is associated, among other things, with the formation of a flagellum, which helps the cell move. In the process of movement, the germ cell rotates around its axis at a speed of 0.1 millimeter per second. That's over thirty centimeters an hour. They need to overcome a distance of more than 20 cm. Somewhere in a couple of hours after intercourse, spermatozoa reach the fallopian tubes, and (if there is an egg) fertilization occurs.
Inside the male body, spermatozoa practically do not move, they are not active and passively move along the seminal ducts along with the seminal fluid due to perist altic contractions of the ducts and the movement of cilia.
Sperm Lifespan
Scientists, together with physiologists, tried to figure out the question of wherespermatozoa are formed and why are they periodically updated? It turned out that the whole process of maturation of germ cells takes more than two months, but a large number of them are obtained. Due to this, men do not have a lack of genetic material.
The viability of spermatozoa lasts only for a month, while they need the right conditions:
- the temperature is not higher than 32 degrees Celsius;- the absence of inflammatory diseases.
And outside the male body, cells retain their mobility for up to a day. Inside the uterus, this time can be extended up to three days.
What is spermatogenesis?
Spermatogenesis is the formation of spermatozoa that occurs under the vigilant regulation of the endocrine system of the body.
It all starts with progenitor cells, which after a few divisions take on the appearance of an adult spermatozoon. Depending on the type of animal, the process of maturation of spermatozoa may differ. So, for example, in chordates, special cells are laid in the embryonic period, which migrate to the rudiments of the gonads and form a pool of cells, which will later become spermatozoa.
Spermatogenesis in humans
The method of sperm formation in humans is no different from that of other vertebrates. The process begins at the time of puberty (from the age of 12) and continues until almost 80 years old.
According to one source, the ripening cyclespermatozoa lasts 64 days, according to others - up to 75 days. But the change of tubular epithelium (which is the substrate for germ cells) occurs at least once every 16 days.
The whole process takes place in the convoluted seminiferous tubules of the testis. On the basement membrane of the tubules are spermatogonia, as well as spermatocytes of the first and second orders, which then differentiate into a mature cell. First, progenitor cells go through several cycles of division by mitosis, and when a sufficient number of them are recruited, they switch to meiosis. As a result of this last division, two daughter spermatocytes are formed, and then two more spermatids. Each of these cells has half the number of chromosomes and can fertilize an egg.
