The release of the ovum from the ovary by the rupturing of the Graafian follicle is called ovulation.
The cells of the Graafian follicle transform into a structure called corpus luteum.
This corpus luteum secretes a large amount of hormone called progesterone which is essential for the maintenance of the endometrial lining of the uterus and the implantation of the fertilized egg.
In case the egg is fertilised, it is implanted in the endometrium.
In case of no fertilisation, the inner lining of the uterus is shed and the menstrual cycle continues.