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Biology > Human Reproduction > Gametogenesis in Humans
Human Reproduction

Gametogenesis in Humans

If you have ever wondered how a baby is born, then it is important to know the process of reproduction in-depth. The biological DNA contained in the sperm are formed using the process called gametogenesis. It consists of different phases after which the male and female sex cells are formed. This article would carefully enlighten you about gametogenesis and oogenesis features.

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Introduction to Gametogenesis

We can simply call it the procedure by which sperms and ova (male and female sex cells) are designed in the male testes and female ovaries respectively. These gametes vary from all the other cells present in the body. This is because their nuclei contain only half the count of chromosomes present in nuclei of somatic cells.

oogenesis

It is vital to note that, meiosis shapes the most major part of the development of gametogenesis. Further, gametogenesis associated with the formation of sperms is called as spermatogenesis. Whereas, the formation of ova is termed as oogenesis. In addition, both oogenesis and spermatogenesis include similar stages of sequential changes; that includes:

Insights about Spermatogenesis

The formation procedure of sperms is known as spermatogenesis. This occurs primarily in the semi­niferous tubules present in the testes. These seminiferous tubules are creased by germinal epithelium. Further, the germinal epithelium largely comprises of primordial germ cells or PGCs. In addition, tall somatic cells termed as Sertoli cells (nurse cells) are also present. Spermato­genesis refers to the formation of spermatids and spermatozoa.

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Creation of Spermatids

This procedure covers three stages; namely:

  • Multiplication Phase: During sexual maturity, the division of undistinguishable primordial germ cells occurs several times due to mitosis. This is majorly to produce a large count of spermatogonia. These are of two kinds: type A and type B. Type A spermatogonia act as the stem cells that divide to create additional spermatogonia. On the other hand, Type В spermatogonia can be thought as the prototypes of male sex cells.
  • Growth Phase: Do remember that, every type В spermatogonium dynamically grows to form a superior primary spermatocyte through nourishment received from the nursing cells. This phase further concludes in the maturation stage.
  • Maturation Phase: Under this, primary spermatocyte experiences two successive divi­sions. These are termed as maturation divisions, and meiotic is the first maturation disunion. Therefore, the primary spermatocyte segregates into two haploid daughter cells known as secondary spermatocytes. Further, both the secondary spermatocytes suffer second maturation separation that is a regular mitotic division. It leads to the creation of four haploid spermatids.

Creation of Spermatozoa

In simple words, the conversion of spermatids to spermatozoa is termed as spermateliosis or spermiogenesis. Further, spermatozoa are later called as sperms. Hence, four sperms are developed from a single sper­matogonium. Once spermiogenesis happens, the sperm heads are fixed in the Sertoli cells, which are finally let loose from the seminiferous tubules through a process termed as spermiation.

Sperms are motile and microscopic cells that remain alive and recollect their capability to fertilize an egg (ovum) from 24 -48 hours right after being free in the female genital tract. For a typical mammalian sperm, the head, neck, together with middle piece and tail are the prime sections.

oogenesis

Sperm

Oogenesis

The effect of gametogenesis in females is associated with the mature female gamete. This is created through a process called oogenesis. This happens in the ovaries or female gonads. There are three phases to oogenesis; namely, multiplication phase, growth phase and maturation phase. Let us try to understand these phases in a precise manner.

  • Multiplication Phase: During foetal development, it should be noticed that certain cells present in the germinal epithelium of the female ovary are bigger than others. Hence, these cells split by mitosis, creating a couple of million oogonia or mother egg cells in each ovary present in the foetus. There are no more oogonia which are formed or augmented after birth.
  • Growth Phase: This particular procedure of the primary oocyte tends to be very long. In this, the oogonium nurtures into bigger primary oocytes. After this, each primary oocyte gets surrounded by a granulosa cells layer to create primary follicle. Later, a large number of follicles get debased during the duration from birth to puberty. Therefore, at puberty around 60,000 to 80,000 primary follicles can be found in each ovary.
  • Maturation Phase: Similar to a primary spermatocyte, every primary oocyte experiences two maturation divisions. However, the outcomes of maturation divisions under oogenesis are quite different to those which occur in spermatogenesis. Considering the first meiotic division, the primary oocyte segregates into two uneven haploid daughter cells. These are known as the large secondary oocyte and a small polocyte.

Later, considering the second maturation separation, the initial polar body might split to create two, second polar bodies. Here, the secondary oocyte once again divides to form unfit daughter cells.

oogenesis

Ovum

A Solved Question for You

Q: What is the name of the particular cells that are capable to form gametes?

Ans: The cells which form gametes are known as germ cells (contrasting to somatic cells).

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