Tertiary Follicle & Meiosis I — NEET Biology
✅ Asked in NEET 2023The secondary follicle soon transforms into a tertiary follicle which is characterised by a fluid filled cavity called antrum. The theca layer is organised into an inner theca interna and an outer theca externa. It is important to draw your attention that it is at this stage that the primary oocyte within the tertiary follicle grows in size and completes its first meiotic division. It is an unequal division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body. The
NTA tests the transformation of secondary follicle into tertiary (Graafian) follicle, specifically focusing on the antrum formation and completion of meiosis I by the primary oocyte. The key concept is understanding unequal meiotic division: the primary oocyte produces a large secondary oocyte (haploid, receives most cytoplasm) and a tiny first polar body (haploid, receives minimal cytoplasm). Students commonly confuse this unequal division with equal meiosis II division or forget that meiosis I is completed at this tertiary stage, not during ovulation. Remember: Tertiary follicle = antrum present + meiosis I complete + secondary oocyte formed. This concept tests understanding of both folliculogenesis and oogenesis simultaneously.
Given below are two statements regarding oogenesis.: Statement I: The primary follicles get surrounded by more layers of granulosa cells, a theca and shows fluid filled cavity antrum. Now it is called secondary follicle. Statement II: Graafian follicle ruptures to release the secondary oocyte from the ovary by the process called ovulation. Choose the correct answer:
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