It is said the oogenesis terminates when the oocyte into a graafian follicle . Why ??

Dear Student,
 
Graafian follicle is a vesicular structure in which oocyte matures to an ovum. The process of the formation of primary oocyte starts at the puberty time. After the beginning of puberty, the ovary alternates between the two phases, namely, follicular phase and luteal phase. The ovarian cycle terminates at the onset of menopause which results into the termination of oogenesis. 
 
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