We explain what spermatogenesis is and the phases into which this process is divided. Also, what does azoospermia and oogenesis consist of?
What is spermatogenesis?
It is called spermatogenesis or spermatocytogenesis. process of generation or production of sperm which takes place inside the male sexual glands (testicles), specifically in the seminiferous tubules, coiled ducts of about 30 to 60 cm. in length and 0.2 mm in width. Between the two testicles of a man there are more than a thousand of these ducts.
Sperm, as is known, They are the gametes or male reproductive cells endowed with half of the individual's genome (haploid or n) and its own mobility through a single flagellum (or tail). They are expelled from the body during ejaculation, along with the rest of the seminal content (semen) and, if they find an egg (female gamete) willing to be fertilized, they fuse to give rise to a new life.
The discovery of the cellular nature of sperm is relatively recent: it coincides with the discovery of cell theory in the 19th century.
the word spermatozoon They were used for the first time in 1827, and by 1841 they were in frequent use, although they were not yet considered reproductive cells. It would be Albert Koeliker years later who would offer the first complete explanation of the phenomenon, based on the seminal fluid of various animals.
spermatogenesis It is triggered in the human body by the release of the hormone GnRH (gonadotropin-releasing hormone), secreted by the hypothalamus; It consists of a successive process of mitosis and meiosis, and has a total duration of approximately between 62 and 75 days.
See also: Metabolism
Phases of spermatogenesis
The creation of sperm involves the following phases:
- Proliferative or spermatogonic phase Type A spermatogonia are formed from germ stem cells: cells that, by mitotic division (mitosis), give rise to type A and type B spermatogonia. The former will continue to replicate and produce both types of cells; The latter, however, will divide into two primary spermatocytes, which in turn will divide into four mature sperm. This first phase takes place during puberty in men, when their reproductive system is activated.
- Meiotic phase or spermatocytogenesis. In this phase, new cell division mechanisms occur, which give rise to haploid cells called spermatidsthrough meiosis processes. This occurs during two stages:
- Meiosis I Each primary (diploid) spermatocyte divides into two secondary (haploid) spermatocytes.
- Meiosis II The secondary spermatocytes divide into two spermatids (haploid), thus obtaining four cells from the first. In the latter, the shape of the mature sperm is already beginning to take shape, and they even present a flagellum.
- Spermiogenesis. This last stage occurs during the maturation of the spermatid to form mature sperm. The flagellum grows to its ideal point, the cell acquires its characteristic pointed shape, reduction of the cytoplasm, elongation of its cell nucleus and development of acrosome. At this time the sperm are released to the center of the seminiferous tubule, ready to be ejaculated.
Azoospermia
This name refers to a disease of the human male reproductive system, consisting of the absence of sperm in male semen. This naturally minimizes the fertility levels of the individual.
This ailment can be determined through studies of semen quality as well as hormonal analysis, since it is attributed to the deficiency of the hormone FSH (Follicle Stimulating Hormone), responsible among others for the testicle to produce sperm.
It should not be confused with aspermia, which is the complete lack of semen during ejaculation.
Oogenesis
Oogenesis is the process equivalent to spermatogenesis, but in the female reproductive system, that is, it is the process of formation and maturation of eggs (female gametes). In mammals, this process produces only a few hundred eggs throughout the woman's fertile life, which occurs in her gonads, the ovaries.
This process is regulated hormonally by the pituitary gland, through the hormone FSH and leutinizing hormone. Like spermatogenesis, this process involves different stages of mitosis and meiosis to finally produce haploid sex cells (n) from diploids (2n).
References
- “Phases of spermatogenesis” in Assisted Reproduction.
- “Spermatogenesis” in Wikipedia, The Free Encyclopedia.
- “Azoospermia: a fertility problem that can be overcome” in Diario La Nación (Argentina)