Anonymous
Dec 11, 2023
Oogenesis in mammals and its regulation?
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Dec 11, 2023
Oogenesis is the process of egg cell (or oocyte) development in mammals. It occurs in the ovaries and involves several stages of cell division and maturation. The regulation of oogenesis is complex and involves various hormonal and molecular factors.
1. Primordial follicle formation: During fetal development, primordial germ cells migrate to the developing ovaries and differentiate into oogonia. These oogonia undergo several rounds of mitotic divisions to form primary oocytes. Each primary oocyte is surrounded by a layer of somatic cells called granulosa cells, forming a primordial follicle.
2. Meiotic arrest: After primordial follicle formation, the primary oocytes enter a prolonged arrest phase called meiotic arrest. This arrest occurs at the diplotene stage of meiosis I and can last for years or even decades, depending on the species.
3. Follicular development: At puberty, a small number of primordial follicles are activated to resume development. This process is regulated by hormonal signals, primarily follicle-stimulating hormone (FSH) from the pituitary gland. FSH stimulates the growth and development of a selected follicle, while the remaining follicles undergo atresia (degeneration).
4. Meiotic resumption: Under the influence of FSH, the selected follicle undergoes further growth and development, and the primary oocyte within it resumes meiosis. Meiosis I is completed, resulting in the formation of a secondary oocyte and a polar body. However, meiosis II is arrested at the metaphase stage until fertilization occurs.
5. Ovulation: The mature follicle eventually ruptures, releasing the secondary oocyte into the fallopian tube in a process called ovulation. Ovulation is triggered by a surge in luteinizing hormone (LH) from the pituitary gland.
6. Fertilization and meiotic completion: If fertilization occurs, the secondary oocyte completes meiosis II, resulting in the formation of a mature egg (ovum) and another polar body. The nuclei of the egg and sperm then fuse to form a zygote.
The regulation of oogenesis involves a complex interplay of hormonal and molecular factors. Hormones such as FSH and LH from the pituitary gland, as well as estrogen and progesterone from the ovaries, play crucial roles in regulating follicular development, meiotic resumption, and ovulation. Additionally, various growth factors, signaling molecules, and transcription factors are involved in the precise control of oocyte development and maturation.
Overall, oogenesis in mammals is a highly regulated process that ensures the production of mature and viable eggs for reproduction.
1. Primordial follicle formation: During fetal development, primordial germ cells migrate to the developing ovaries and differentiate into oogonia. These oogonia undergo several rounds of mitotic divisions to form primary oocytes. Each primary oocyte is surrounded by a layer of somatic cells called granulosa cells, forming a primordial follicle.
2. Meiotic arrest: After primordial follicle formation, the primary oocytes enter a prolonged arrest phase called meiotic arrest. This arrest occurs at the diplotene stage of meiosis I and can last for years or even decades, depending on the species.
3. Follicular development: At puberty, a small number of primordial follicles are activated to resume development. This process is regulated by hormonal signals, primarily follicle-stimulating hormone (FSH) from the pituitary gland. FSH stimulates the growth and development of a selected follicle, while the remaining follicles undergo atresia (degeneration).
4. Meiotic resumption: Under the influence of FSH, the selected follicle undergoes further growth and development, and the primary oocyte within it resumes meiosis. Meiosis I is completed, resulting in the formation of a secondary oocyte and a polar body. However, meiosis II is arrested at the metaphase stage until fertilization occurs.
5. Ovulation: The mature follicle eventually ruptures, releasing the secondary oocyte into the fallopian tube in a process called ovulation. Ovulation is triggered by a surge in luteinizing hormone (LH) from the pituitary gland.
6. Fertilization and meiotic completion: If fertilization occurs, the secondary oocyte completes meiosis II, resulting in the formation of a mature egg (ovum) and another polar body. The nuclei of the egg and sperm then fuse to form a zygote.
The regulation of oogenesis involves a complex interplay of hormonal and molecular factors. Hormones such as FSH and LH from the pituitary gland, as well as estrogen and progesterone from the ovaries, play crucial roles in regulating follicular development, meiotic resumption, and ovulation. Additionally, various growth factors, signaling molecules, and transcription factors are involved in the precise control of oocyte development and maturation.
Overall, oogenesis in mammals is a highly regulated process that ensures the production of mature and viable eggs for reproduction.
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