✅ OVOGÉNESIS ¿Como se forman los ovocitos? | EMBRIOLOGÍA HUMANA 📚
Ovogenesis Process Overview
The process of ovogenesis, detailing the transformation of oogonia into mature oocytes in the ovaries, is discussed. The phases of ovogenesis are outlined, including multiplication, growth, and maturation.
Ovogenesis Phases
- Ovogenesis can be divided into phases: multiplication, growth, and maturation. Some sources describe ovogenesis occurring in two stages: prenatal (before birth) and postnatal (after birth).
- During the prenatal stage, multiplication phase begins with primordial germ cells reaching the female gonads. These cells proliferate through mitosis to become oogonia, each containing 46 chromosomes.
- In the growth phase, oogonia increase in size due to nutrient accumulation in their cytoplasm, transforming into primary oocytes surrounded by a layer of flattened follicular cells forming primordial follicles.
- Maturation phase starts as primary oocytes replicate DNA and enter prophase of the first meiotic division. Before birth, they enter a latency stage called diplotene until puberty due to an inhibitor secreted by follicular cells.
- By late fifth month of fetal development in each ovary approximately 7 million oogonia form but decrease over time. At birth, there are around 600k to 800k primary oocytes per ovary which further reduce before puberty.
Postnatal Development
- After birth, most primary oocytes degenerate except for about 40k per ovary at puberty; only a few hundred will mature monthly until menopause.
- Primary oocytes remain dormant until puberty when maturation resumes. They grow larger during this phase and upon ovulation undergo meiotic division resulting in secondary oocyte and polar bodies.
- If fertilization occurs with a spermatozoon, the secondary oocyte completes meiosis II forming a zygote; if not fertilized, degeneration occurs leading to a new cycle where some primary oocytes are stimulated monthly.
Conclusion