The Graafian follicle ruptures to release the ovum from the ovary by the process called:

Ovulation

Female gamete mother cell present in the fetal ovary or oogonia enters prophase-I of the meiosis-I and gets arrested at this stage and becomes a primary oocyte.

A layer of granulosa cells is laid on the primary oocyte and it is now called primary follicles.

Primary folicles get surrounded by more layers of granulosa cells and a new theca to form a secondary follicle.

After birth, the secondary follicles develops a fluid filled cavity called antrum, and becomes tertiary follicle.

After puberty, the tertiary follicle matures into Graafian follicle.

Graafian follicles rupture to release the secondary oocyte and this process is called ovulation.

The secondary oocyte completes meiosis II to form ovum and a second polar body during fertilisation.