Men can be no less curious than women. Therefore, some of them are very interested in the structure of their own body, and especially its most important organs. The bold then become doctors, and the rest simply read the necessary literature. The most important questions remain: Where does the sperm form? What does he look like? How many lives? And how is it moving? Let's try to answer them so that everyone understands.
Definition
Before answering the question of where the sperm is formed, you need to understand what it is. A sperm is the reproductive cells of animals and humans. As a rule, these cells are able to actively move, which is vital in order to get to the egg and fertilize it.
Compared to the female reproductive cell, the sperm are small, nimble, and at the same time a large number of them mature in the body (unlike the egg, which alone is the crown of the woman’s thirty-day endocrine system).
The structure of this germ cell indicates that all animals and fungi had a common ancestor - a unicellular organism. Traditionally, any male germ cells, even in plants, are commonly called spermatozoa, although the definition of “sperm” as well as anterozoids also apply to them.
Sperm in animals
Oddly enough, but animals are not very different from humans in the structure and function of germ cells. Where do sperm cells form? How do they look? Are there any fundamental changes?
An ordinary animal sperm 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, there are enzymes in the head for incorporation into the egg and centriole. In the intermediate part, it is the neck, a large mitochondria is located, which provides the flagellum with energy and supports its movement.
Exceptions to the above sample are some types of aquarium fish, whose sperm have two flagella. This also applies to crustaceans (they can have from three or more “tails” in germ cells). But roundworms have offended evolution by moving cells - in his entire body there are no cilia or flagella. The germ cells of these animals have a plastic cell wall, which allows them to move with the help of pseudopods. Tritons have a fin on the sperm. But variations occur not only at the tails, but also at the heads. If in humans they are ellipse-like, then mice and rats can boast of a hook-like shape.
The size of germ cells in men is extremely small - from tens to hundreds of micrometers. Such a spread is in no way related to the size of the adult.
Sperm discovery
Before scientists thought about the question “Where does the sperm form?”, They had no idea that there are special cells involved in the reproduction of humans and animals. And in general, the structure of living tissues had a very distant idea.
The revolution in science took place in the mid-seventeenth century, when the Dutchman Antoine Levenguk invented a microscope and began to examine various objects: 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, Levenguk first set all the experiments on himself, so the sperm of a person were described first, and only then other animals. The idea that these "animals" are involved in conception quickly came to Antoine's mind, which he did not fail to report to the British Scientific Society.
But this hypothesis was rejected, and for another hundred years sperm cells were considered parasites in the male body, and had nothing to do with fertilization. Only at the beginning of the nineteenth century did the Italian Spallanzani prove the veracity of this theory.
Structure
If you do not take into account the length of the flagellum, then the sperm is the smallest cell in the human body, about 55 micrometers. Such small dimensions allow him to quickly move in 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 more dense due to the condensation of genetic material;
- the cytoplasm is separated into a separate "cytoplasmic drop";
- only those organelles that are vital to the cell remain.
- The sperm head 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 form. In the head are:
- a nucleus having a haploid set of chromosomes. It is necessary 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 provides movement of the tail. - The middle part or neck is the narrowing between the head and tail. It contains mitochondria, which produces energy for flagellum movements.
- The tail or flagellum is the thin mobile part of the sperm. It performs rotational translational movements that allow the cell to achieve the goal.
Function
The method and place of sperm formation are closely related to its functions. And the main one of them is penetration into the egg and fertilization. To fulfill this function, nature provided for sperm motility, mass character and chemical “attractiveness”.
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 health, has no bad habits, has done all the vaccinations in time (especially against mumps), then his sex cells will be ready to perform their function at any time.
Traffic
The formation of sperm in men is associated, inter alia, 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. This is more than thirty centimeters per hour. They need to cover a distance of more than 20 cm. Somewhere in a couple of hours after sexual intercourse, the sperm reach the fallopian tubes, and (if there is an egg) fertilization occurs.
Inside the male body, sperm cells practically do not move, they are inactive and passively move along the seminal ducts along with seminal fluid due to peristaltic contractions of the ducts and cilia.
Sperm life span
Scientists, along with physiologists, tried to figure out the question of where sperm cells form and why are they periodically updated? It turned out that the entire process of germination of germ cells takes more than two months, but a large number of them are obtained. Due to this, men have no shortage of genetic material.
Sperm viability lasts only for a month, while they need the right conditions:
- temperature is not higher than 32 degrees Celsius;
- lack 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 sperm cells that occurs under the vigilant regulation of the endocrine system of the body.
It all starts with progenitor cells that, after several divisions, take on the form of an adult sperm. Depending on the type of animal, sperm maturation may vary. So, for example, in chordates, special cells are laid in the embryonic period that migrate to the rudiments of the gonads and form a pool of cells, which will subsequently become spermatozoa.
Spermatogenesis in humans
The method of sperm formation in humans is no different from that in other vertebrates. The process begins at the time of puberty (from 12 years old) and lasts almost to 80 years.
According to some sources, the sperm maturation cycle lasts 64 days, according to others - up to 75 days. But the change of tubular epithelium (which is a substrate for germ cells) occurs no less than once every 16 days.
The whole process takes place in the convoluted seminiferous tubules of the testis. Spermatogonia are located on the basal membrane of the tubules, as well as spermatocytes of the first and second orders, which then differentiate into a mature cell. First, the progenitor cells undergo several cycles of mitosis division, and when a sufficient number of them is 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 a half set of chromosomes and can fertilize an egg.