Oogenesis in Non-Human Mammals
In non-human mammals, oogenesis begins in the germinal epithelium of the ovary, which creates ovarian follicles. Oogenesis involves three stages: oocytogenesis, ootidogenesis, and maturation to form the ovum. Folliculogenesis is a separate sub-process that accompanies and supports all three oogenetic sub-processes.
Formation of Oogonia
Oogenesis starts with folliculogenesis, oocytogenesis, and ootidogenesis. Oogonia become oocytes through meiosis during embryonic development. Meiosis involves DNA replication and crossing over and ends in early prophase.
Preservation of Meiotic Arrest
- Mammalian oocytes are continued in meiotic prophase arrest: Mammalian oocytes are arrested in meiotic prophase due to a lack of cell cycle proteins initially, but later cyclic AMP plays a crucial role. Follicles surrounding the oocyte help in preserving meiotic arrest. Granulosa cells, which make up the follicles are connected by gap junctions. Cyclic GMP, produced by granulosa cells, enters the oocyte and prevents meiotic arrest breakdown.
- The reinitiation of meiosis and stimulation of ovulation by the luteinizing hormone: As follicles grow, they acquire receptors for the luteinizing hormone, which restarts meiosis in the oocyte, leading to ovulation of a fertilizable egg. The luteinizing hormone acts on receptors in the granulosa cells, causing a decline in cyclic GMP and restarting meiosis in the oocyte. Meiosis stops again at the second metaphase until fertilization. The luteinizing hormone also restores gene expression, leading to ovulation.
What is Oogenesis?
Oogenesis is the process that describes how a mature egg in females develops. Oogenesis is part of a very important process called gametogenesis. Oogenesis helps to ensure that the human species keeps on continuing on the face of the Earth. Oogenesis describes the remarkable journey an oocyte undergoes after it originates from the primordial germ cell. The whole intricate process of oogenesis takes place in the ovarian follicles present in the ovaries. Understanding the process of oogenesis helps us to comprehend female fertility, the menstrual cycle, and female reproductive health.
Table of Content
- What is Gametogenesis?
- What is Oogenesis?
- Process of Oogenesis
- Phases of Oogenesis
- Ovulation
- Oogenesis in Non-Human Mammals
- Ovarian Aging
- Hormonal Control of Oogenesis
- Significance of Oogenesis
- Oogenesis Timeline and Stages
- FAQs – What is Oogenesis?