Aprimary oocyte residing in a primordial follicle becomes a secondary oocyte a primary oocyte residing in a primordial follicle becomes a secondary oocyte in the primary follicle in the vesicular follicle in the secondary follicle only if fertilized after ovulation

The primary oocyte residing in a primordial follicle grows and becomes primary follicle and becomes a secondary oocyte and into vesicular follicle during the meiosis I. During the meiosus II if the secondary oocyte will not be fertilize then the vesicular follice becomes the corpus luteum until it degenerates.