The spermatogenesis is the process of formation and development of male gametes, better known as sperm. It occurs in all male representatives of the Animal kingdom that reproduce sexually, and in humans it begins during puberty and occurs in the testicles..
Sperm are male gametes, that is, the sex cells that men produce when they are sexually mature..
The main function of these small flagellated cells is to pass part of the genetic information of the organism that produces them to a new generation through sexual reproduction..
Like their female counterparts -the ovules- sperm are produced by a special type of cell division called meiosis, from a set of cells known as germ cells.
It is because of meiosis that the sex cells, male and female, are cells haploid or, what is the same, cells with half of the genetic information of the person who produces them.
The germ cells that give rise to sperm are found in the testicles, which are two and are part of the male reproductive system.
Inside the testicles, sperm are continuously produced in tubes called seminiferous tubules, from cells called spermatogonia, which are undifferentiated cells with the complete genetic load of the individual that produces them, that is, they are diploid.
The whole process of spermatogenesis can be seen as divided into three phases that involve: cell proliferation, meiosis and differentiation or maturation.
Spermatogenesis is the process of differentiation of a set of diploid cells - spermatogonia - into sperm cells that will then mature to become functional sperm.
It occurs for the first time at the beginning of puberty and continues throughout the adult life of male human beings. It is a highly orderly process that results in the daily production of millions of sperm once sexual maturity is reached..
During spermatogenesis, cell division events occur, both due to mitosis as for meiosis, and also of differentiation or remodeling.
The stages or phases of spermatogenesis are three: one of proliferation and differentiation of germ cells, another of meiotic division and a last of transformation of spermatids into spermatozoa, also known as spermiogenesis.
Spermatogenesis (generation of sperm) occurs inside the male gonads -the testes- specifically in some internal regions of these known as seminiferous tubules.
Two different types of cells are found in this region of the male reproductive system: Sertoli cells and spermatogenic or spermatogenic cells..
Sertoli cells nourish and protect spermatogenic cells, which are the cells that give rise to the different precursors of sperm; therefore, spermatogenic cells are found in different stages of maturation in the seminiferous tubules..
Among these cells are the spermatogonia, which are cells derived from germ cells that, when dividing, produce new spermatogonia and also the other types of cells that are formed during the differentiation of sperm, this means that they are precursor cells.
These cells are in the seminiferous tubules, but in the outermost part of the epithelium that forms them. As they divide, their daughter cells migrate to the center of these ducts, where they mature.
Spermatogenesis is the phase of proliferation in which spermatocytes are formed, which are derived from spermatogonia..
Spermatogonia are diploid cells (2n), which means that they are cells with all the genetic information of the individual to which they belong. These divide asexually by mitosis, generating new spermatogonia and another type of cells called primary spermatocytes.
Primary spermatocytes are cells that stop dividing by mitosis and begin the first division by meiosis (also known as Meiosis I).
The spermatocytes that begin their maturation, that is, that go through mitosis and begin meiosis, remain connected to each other through what experts have called "cytosolic bridges", since nuclear divisions occur but there is no separation full cytosolic.
These cells remain together until the later stages of maturation, resulting in the synchronized release of groups of cells rather than individual cells..
Meiosis is one of the fundamental stages of spermatogenesis, because thanks to this special type of division the genetic load of an individual is reduced by half (cells are formed haploid). Occurs in primary spermatocytes derived from diploid spermatogonia.
The first part of meiosis, also known as Meiosis I, it has to do with the combination of homologous chromosomes, that is, of the maternal and paternal chromosomes that diploid organisms inherit from their parents. These chromosomes are duplicated and separated into new cells..
The Meiosis II it is very similar to mitosis, with the difference that the genetic material is not duplicated; instead, the sister chromatids that make up each chromosome separate, resulting in 4 haploid cells with a different combination of genes.
The first meiotic division of primary spermatocytes leads to their progression to secondary spermatocytes. When these cells go through meiosis II, then they differentiate into spermatids, which are already haploid cells..
Spermatogonia are immobile and poorly differentiated cells, while spermatids are more differentiated cells that will give rise to fully differentiated, motile spermatozoa..
The phase that involves the maturation of spermatids in spermatozoa is known as spermiogenesis.
Spermatids, during this process, undergo important morphological changes:
Spermatids, during the maturation process, migrate from the seminiferous tubules to the epididymis, which is another kinky tube inside the testes. There they are stored and continue their differentiation, until they are expelled with the seminal fluid during ejaculation..
The complete maturation of sperm occurs when they undergo a process called training, once found in the female genital tract.
Oogenesis is the process analogous to spermatogenesis, that is, it is the process by which female gametes are formed, better known as ovules. Here are the main differences with spermatogenesis:
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