Question

Explain the changes the primary oocyte undergoes while in different follicular stages before ovulation.

Answer 1

Changes in the primary oocyte:

• Each primary oocyte gets surrounded by a single layer of granulosa cells, known as primary follicles. 
• Primary follicles get surrounded by more layers of granulosa cells and a new theca called secondary follicles. 
• A secondary follicle transforms into tertiary follicle characterised by a fluid filled space, the antrum. 
• Primary oocyte undergoes first meiotic division and produces two unequal haploid cells: a large haploid secondary oocyte and a tiny first polar body. 
• The tertiary follicle further changes into the mature Graafian follicle. 
• The secondary oocyte forms a new membrane called zona pellucida around it.