The germinal epithelial cells divide repeatedly until many diploid aagonia are formed. The oogonia grow Ic form primary oocytes. Each primary oocyte then gets surrounded by a layer of granulosa cells and then called the primary follicle. The primary follicles get surrounded by more layers of granulosa cells and called secondary follicies. The secondary follicie soon transforms into a tertiary follicle which is characterised by a fluid filled cavity called antrum. The primary oocyte within the tertiary follicle undergoes meiotic division to become a secondary oocyte and a first polar body (haploid). The tertiary follicie further changes into the mature follicte to Graaflan follicle, The Graafian follicle now ruptures to release the secondary oocyte (ovum) from the ovary by the process called ovulation.