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Related Concept Videos

Oogenesis02:07

Oogenesis

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In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from the equivalent procedure of spermatogenesis in males. First, meiotic divisions during oogenesis are asymmetric, meaning that a large oocyte (containing most of the cytoplasm) and minor polar body are produced as a result of meiosis I, and again following meiosis II. Since only oocytes will go on to form embryos if fertilized, this unequal...
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Oogenesis01:22

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Oogenesis,  the process of developing egg cells (female gametes), occurs within the ovaries and is fundamental to female fertility. This sequence begins during fetal development when diploid oogonia in the developing ovaries undergo mitotic divisions to produce primary oocytes. By birth, these primary oocytes enter prophase I of meiosis but become arrested in this stage, remaining suspended until puberty.
Each primary oocyte is surrounded by a layer of pre-granulosa cells, forming what is...
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Folliculogenesis01:20

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Folliculogenesis is the development of ovarian follicles, the specialized structures within the ovarian cortex where oogenesis, or egg development, occurs. This process is essential for female reproductive health and begins during fetal development when primordial follicles are formed. Each primordial follicle comprises a primary oocyte in the center, surrounded by a single layer of squamous pre-granulosa cells. These follicles remain dormant in late prophase I of meiosis until triggered by...
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Parental Care00:55

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Many animals exhibit parental care behavior, including feeding, grooming, and protecting young offspring. Parental care is universal in mammals and birds, which often have young that are born relatively helpless. Several species of insects and fish, as well as some amphibians, also care for their young.
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Formation of Muscle Fibers from Myoblasts01:13

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De novo myogenesis, or the formation of muscle fibers, begins during the early embryonic stages. The skeletal muscle is formed from somites– blocks of embryonic cell layers. The somites are further divided into dermatomes, myotomes, sclerotomes, and syndetomes. Among these, the myotomes give rise to muscle fibers.
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The gonads, namely the testes in males and the ovaries in females, are pivotal in producing gonadal hormones that orchestrate the intricate processes of sexual development and reproduction.
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Related Experiment Video

Updated: Feb 25, 2026

Whole Ovary Immunofluorescence, Clearing, and Multiphoton Microscopy for Quantitative 3D Analysis of the Developing Ovarian Reserve in Mouse
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Whole Ovary Immunofluorescence, Clearing, and Multiphoton Microscopy for Quantitative 3D Analysis of the Developing Ovarian Reserve in Mouse

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Neo-oogenesis in mammals.

Tania Janeth Porras-Gómez1, Norma Moreno-Mendoza2

  • 1Department of Cell Biology and Physiology,Instituto de Investigaciones Biomédicas,Universidad Nacional Autónoma de México,Ciudad Universitaria,Apartado Postal 70228,México D.F. 04510,México.

Zygote (Cambridge, England)
|August 8, 2017
PubMed
Summary

Neo-oogenesis, the formation of new oocytes in adult mammals, is debated. While evidence suggests ovarian renewal, the scientific community remains divided due to reproducibility issues and conflicting dogmas.

Keywords:
Germ line stem cellsMammalian ovaryNeo-oogenesisOvarian stem cellsPrimordial germ cells

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Area of Science:

  • Reproductive Biology
  • Developmental Biology
  • Cell Biology

Background:

  • The dogma of finite oocyte reserve at birth (Zuckerman's hypothesis) has long dominated reproductive biology.
  • Recent studies propose neo-oogenesis, the renewal of the follicular reserve from germline stem cells in adult ovaries.
  • Evidence for neo-oogenesis has been reported across various mammalian species, including humans, mice, pigs, and bats.

Purpose of the Study:

  • To critically review the existing literature on neo-oogenesis in mammals.
  • To evaluate the arguments supporting and opposing the concept of neo-oogenesis.
  • To address the controversy surrounding the existence of neo-oogenesis in adult mammalian ovaries.

Main Methods:

  • Literature review of studies investigating oogenesis in adult mammals.
  • Analysis of evidence for mitotic activity in adult ovaries.
  • Comparison of findings across different mammalian species and experimental models.
  • Critical evaluation of reproducibility and scientific debate.

Main Results:

  • Conflicting evidence exists regarding neo-oogenesis, with some studies reporting germline stem cell activity and others failing to reproduce these findings.
  • The concept challenges the long-standing Zuckerman's hypothesis.
  • The debate involves two distinct scientific positions, with ongoing research utilizing diverse animal models.

Conclusions:

  • The existence of neo-oogenesis in adult mammals remains a controversial topic.
  • Further research and reproducible evidence are required to resolve the debate.
  • Understanding neo-oogenesis has significant implications for reproductive potential and fertility preservation.