Oogenesis | Gametogenesis | Embryology🩺

#oogenesisoverview #pharmacology #renataloogenesis #primaryoocyte #postnataloogenesis #postnataloogenesis #ovulation #embryology #gynaecology #femalereproduction Oogenesis | Gametogenesis | Embryology🩺 Like this video? Sign up now on our website at https://www.DrNajeebLectures.com to access 800+ Exclusive videos on Basic Medical Sciences & Clinical Medicine. These are premium videos (NOT FROM YOUTUBE). All these videos come with English subtitles & download options. Sign up now! Get Lifetime Access for a one-time payment of $45 ONLY! Sign up now on our website at https://members.drnajeeblectures.com/ --------------------------------------------------------------------------------------------------------------------------- Why sign up for premium membership? Here's why! Membership Features for premium website members. 1. More than 800+ Medical Lectures. 2. Basic Medical Sciences & Clinical Medicine. 3. Mobile-friendly interface with android and iOS apps. 4. English subtitles and new videos every week. 5. Download option for offline video playback. 6. Fanatic customer support and that's 24/7. 7. Fast video playback option to learn faster. 8. Trusted by over 2M+ students in 190 countries. --------------------------------------------------------------------------------------------------------------------------- ▬▬▬▬▬▬▬▬▬▬ Contents of this video ▬▬▬▬▬▬▬▬▬▬ Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage. Oogenesis: Oogenesis starts with the process of developing primary oocytes, which occurs via the transformation of oogonia into primary oocytes, a process called oocytogenesis. Oocytogenesis is complete either before or shortly after birth. Number of primary oocytes: It is commonly believed that, when oocytogenesis is complete, no additional primary oocytes are created, in contrast to the male process of spermatogenesis, where gametocytes are continuously created. In other words, primary oocytes reach their maximum development at ~20 weeks of gestational age, when approximately seven million primary oocytes have been created; however, at birth, this number has already been reduced to approximately 1-2 million. Two publications have challenged the belief that a finite number of oocytes are set around the time of birth. The renewal of ovarian follicles from germline stem cells (originating from bone marrow and peripheral blood) has been reported in the postnatal mouse ovary. In contrast, DNA clock measurements do not indicate ongoing oogenesis during human females' lifetimes. Thus, further experiments are required to determine the true dynamics of small follicle formation. Ootidogenesis: The succeeding phase of ootidogenesis occurs when the primary oocyte develops into an ootid. This is achieved by the process of meiosis. In fact, a primary oocyte is, by its biological definition, a cell whose primary function is to divide by the process of meiosis. However, although this process begins at prenatal age, it stops at prophase I. In late fetal life, all oocytes, still primary oocytes, have halted at this stage of development, called the dictyate. After menarche, these cells then continue to develop, although only a few do so every menstrual cycle. Meiosis I: Meiosis I of ootidogenesis begins during embryonic development, but halts in the diplotene stage of prophase I until puberty. The mouse oocyte in the dictyate (prolonged diplotene) stage actively repairs DNA damage, whereas DNA repair is not detectable in the pre-dictyate (leptotene, zygotene and pachytene) stages of meiosis. For those primary oocytes that continue to develop in each menstrual cycle, however, synapsis occurs and tetrads form, enabling chromosomal crossover to occur. As a result of meiosis I, the primary oocyte has now developed into the secondary oocyte and the first polar body. Meiosis II: Immediately after meiosis I, the haploid secondary oocyte initiates meiosis II. However, this process is also halted at the metaphase II stage until fertilization, if such should ever occur. If the egg is not fertilized, it is disintegrated and released (menstruation) and the secondary oocyte does not complete meiosis II (and doesn't become an ovum). When meiosis II has completed, an ootid and another polar body have now been created. The polar body is small in size. --------------------------------------------------------------------------------------------------------------------------- Join this channel to get access to the perks: Sign up now on our website at https://members.drnajeeblectures.com/ Follow us on Facebook:- https://www.facebook.com/DrNajeeb/ Follow us on Instagram:- https://www.instagram.com/drnajeeblectures/