Question

What is oogenesis? Give a brief account of oogenesis

Answer 1

Oogenesis:

1. The process of female gamete production is known as oogenesis.
2. This process occurs before birth inside the fetus.
3. The stages of oogenesis lead to the production of primary oocytes.
4. Oogenesis begins with the oogonium, a germ cell that undergoes mitosis to multiply.

There are three phases to oogenesis; namely, the multiplication phase, growth phase, maturation phase, and ovulation phase.

i) Multiplication phase:

1. This phase occurs during the fetal development process.
2. There are a few unusual-looking larger cells found in the germinal epithelium of the ovary.
3. These cells undergo mitotic division and produce a couple of million oogonia or mother egg cells.
4. This division is the last division that occurs during the fetal, no more divisions occur after the birth of the baby.
5. Hence, it is also called a pre-natal phase.

ii) Growth phase:

1. In this phase, the initial oocyte develops and it is quite time-consuming.
2. The oogonium grows into larger primary oocytes.
3. To form a primary follicle, each primary oocyte is then surrounded by a layer of granulosa cells.
4. During the period from infancy until adolescence, a huge number of follicles degrade.
5. As a result, each ovary contains around 60,000 to 80,000 primary follicles during puberty.

iii) Maturation phase:

1. Every primary oocyte goes through two stages of development.
2. The consequences of maturation divisions in oogenesis, on the other hand, are significantly different from those in spermatogenesis.
3. The original oocyte divides into two unequal haploid daughter cells during the first meiotic division.
4. The giant secondary oocyte and the little podocyte are the two types of oocytes.
5. While the secondary oocyte arrests in the metaphase stage of meiosis-II.

iv) Ovulation phase:

1. The process of production of the ovum is called ovulation.
2. This process occurs at the stage of puberty.
3. The primary oocytes become larger in size when the menstrual cycle begins,
4. The follicle cells increase in number, causing the follicle to become larger.
5. Some nursing oocytes degenerate in the normal course of things, leaving just one follicle to develop.
6. The main oocyte completes its primary meiotic division and becomes a secondary oocyte when a follicle reaches maturity.
7. Even if the second meiotic division has not occurred, the follicle cracks, and a secondary oocyte is discharged into the fallopian tube shortly after.
8. Ovulation occurs thus releasing a secondary oocyte from the ovaries.