Zona Pellucida & Oogenesis — NEET Biology
✅ Asked in NEET 2026Can you think of any advantage for this? Does the first polar body born out of first meiotic division divide further or degenerate? At present we are not very certain about this. The tertiary follicle further changes into the mature follicle or Graafian follicle. The secondary oocyte forms a new membrane called zona pellucida surrounding it. The Graafian follicle now ruptures to release the secondary oocyte (ovum) from the ovary by the process called ovulation. Can you identify major differences between spermatogenesis and oogenesis?
The zona pellucida is a transparent glycoprotein membrane that forms around the secondary oocyte before ovulation, protecting the egg and playing a crucial role in fertilization and early development. Students often confuse zona pellucida with the corona radiata (outer layer of follicle cells) or forget its functions entirely. Remember: zona pellucida is secreted by the oocyte itself, not by surrounding cells, and it remains intact during fertilization to prevent polyspermy. NTA tests this concept because understanding oogenesis stages and egg structure is fundamental to reproductive biology—zona pellucida's role in preventing multiple sperm entry directly relates to fertilization mechanisms tested frequently.
Arrange the cell layers/structures around the female gamete from outer to inner: A. Zona pellucida, B. Perivitelline space, C. Corona radiata, D. Plasma membrane of ovum.
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