Answer:
Spermatogenesis is a process whose main function is the production of sperm. It consists of different phases and is performed inside the testicles, in rounded structures called seminiferous tubules.
Once formed, the sperm are expelled to the center of the tubule and transported to the epididymis (upper part of the testicle), where their final maturation takes place. Mature sperm are expelled in the ejaculate and, after training, are already able to fertilize the ovum.
Explanation:
There are three basic stages during sperm formation: proliferative phase, meiotic phase and spermiogenesis.
1. Proliferative phase
It is also called the spermatogonic phase. From a germinal stem cell, type A spermatogonias are formed. These, by mitosis (cell division), will give rise to type A and B spermatogonias:
Type A: will continue to replicate and may lead to type A and B spermatogonia.
Type B: will lead to a primary sperm that, in turn, will result in four mature sperm once the spermatogenesis is over.
Once the reproductive age of man (puberty or adolescence) has arrived, these cells will divide multiple times to form a type of cell called the primary spermatocyte. Throughout these divisions, some cellular changes are taking place.
It is known as a proliferative phase because of the multitude of mitosis that occur. The main objective is to form many sperm precursor cells, that is, many sperm cells.
2. Meiotic phase
Also known as spermatocytogenesis, it is the stage at which a new type of cell division, meiosis, begins, which reduces genetic information by half. Thanks to it, haploid cells called spermatids are produced.
We can divide meiosis into two sub-stages:
Meioisis I
Each primary spermatocyte gives rise to two haploid secondary spermatocytes.
Meioisis II
from each secondary spermatocyte two spermatids are produced, so, in total, from each primary spermatocyte (diploid), we obtain four spermatids (haploids).
These cells are already very similar to sperm: we can already see in them the formation of a small scourge.
3. Spermiogenesis
In the last stage of sperm formation, the final maturation of spermids occurs to give rise to mature sperm.
Its tail increases in size and gives rise to the scourge, which will allow its development. The sperm head decreases and acquires the pointed shape that characterizes it by the reduction of the cytoplasm, the lengthening of the nucleus and the formation of the acrosome.
Finally, mature sperm are released to the center of the seminiferous tubule. Although at this time the sperm is already prepared to be ejaculated, it will be necessary to go through the training process to be able to fertilize the ovum.
Naturally, the training occurs on the path that the sperm uses in the female reproductive tract until it reaches the egg. However, it is also possible to carry it out in the laboratory in case it is necessary to resort to in vitro fertilization.