We explain what spermatogenesis is and the phases into which this process is divided. Also, what is azoospermia and oogenesis?
What is spermatogenesis?
Spermatogenesis or spermatocytogenesis is called the process of generation or production of sperm, which takes place inside the male sex glands (testes), 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 man there are more than a thousand of these ducts.
The spermatozoa, as is known, are the gametes or cells reproductive reproductive organs, endowed with half of the individual's genome (haploid orn) and self-mobility by means of a single flagellum (or tail).They are expelled from the body during ejaculation, along with the rest of the seminal content (semen) and, upon finding an ovum (female gamete) ready 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 the cell theory in the 19th century.
The wordspermatozoon it was used for the first time in 1827, and already in 1841 it was in frequent use, although they were not yet considered as 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 is triggered in the man's body by the release of the hormone GnRH (gonadotropin-releasing hormone), secreted by the hypothalamus; consists of a successive process of mitosis Y meiosis, and has an approximate total duration of between 62 and 75 days.
Phases of spermatogenesis
The creation of sperm involves the following phases:
- Proliferative or spermatogon phase. Type A spermatogonia are formed from the 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, on the other hand, will divide into two primary spermatocytes, which in turn will divide into four mature spermatozoa. This first phase takes place in the man's puberty, when his reproductive system is activated.
- Meiotic phase or spermatocytogenesis. In this phase, new mechanisms of cell division are produced, which give rise to haploid cells calledspermatids, through meiosis processes. This occurs during two stages:
- Meiosis I. Each primary (diploid) spermatocyte divides into two secondary (haploid) spermatocytes.
- Meiosis II. Secondary spermatocytes divide into two spermatids (haploid), thus obtaining four cells from the first. In the latter, the shape of the mature sperm begins to form, 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, reducing the cytoplasm, lengthening its cell nucleus and development of acrosome. At this time the sperm are released into the center of the seminiferous tubule, ready to be ejaculated.
Azoospermia
It is called by this name to a disease of the male reproductive system human, consisting of the absence of sperm in male semen. This naturally minimizes the fertility levels of the individual.
This ailment can be determined by studies of the quality of the semen, as well as analysis hormonal, 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 the ovules (female gametes). In the mammalsThis process produces only a few hundred eggs throughout a woman's fertile life, which occurs in her gonads, the ovaries.
This process is hormonally regulated by the pituitary gland, by means of the FSH hormone and the leutinizing hormone. Like spermatogenesis, this process involves different stages of mitosis and meiosis to eventually produce haploid (n) sex cells from diploid (2n) cells.