Human reproduction - Oogenesis | Biology | CUET| Akanksha Dubey скачать в хорошем качестве

Human reproduction - Oogenesis | Biology | CUET| Akanksha Dubey

OOGENESIS 00:00 Introduction 5:12 Formation of oogonia 20:32 Discussion about follicles 27:56 Fate of secondary oocyte 33:38 Explanation through flow chart The process by which female ovaries produce eggs or ova, is known as oogenesis. Oocytes (egg cells) are developed and matured from the primordial germ cells. The main steps are summarized as follows: 1. Development of the Fetus- During embryonic development, primordial germ cells (PGCs) go to the ovaries. 2. Formation of Oogonia: PGCs undergo differentiation into oogonia, the precursors of egg cells. 3. Mitosis: To increase the number of cells, oogonia goes through several rounds of mitosis. 4. Primary Oocytes: The majority of oogonia have matured into primary oocytes by the time of delivery. At this point in meiosis, these cells enter prophase I and are stopped. A female has a limited quantity of primary oocytes at birth. 5. Childhood to Puberty- The primary oocytes remain dormant in the ovaries until puberty. They are surrounded by a layer of granulosa cells and remain in the arrested stage of prophase I of meiosis. 6. The Menstrual Cycle and Puberty-Although several primary oocytes start to grow during the menstrual cycle, only one usually completes the oogenesis process each month. 7. Follicular Phase: A primary oocyte undergoes meiosis again and matures into a secondary oocyte in response to hormone cues (FSH). 8. After completing meiosis I, the secondary oocyte produces a polar body, which is a tiny, non-functioning cell. 9. The process of Ovulation- Ovulation is the process by which the ovary releases the secondary oocyte. It is waiting for fertilization while in meiosis's second metaphase. 10. The process of fertilization- The secondary oocyte completes meiosis II and produces a mature ovum (egg) and another polar body if it is fertilized by sperm. 11. A zygote, which has the potential to develop into an embryo, is created when the mature ovum unites its genetic material with that of the sperm.