during this phase, several follicles in the ovary begin to develop. the developing follicles secrete oestrogen. of these, only one matures to form the graafian follicle while the rest break down. this phase ends with ovulation is the release from the graafian follicle of an egg cell or ovum and this occurs about 14 days after the start of menstruation. while the graafian follicle is developing, the uterine lining perpares itself for receiving an embryo. in a women who has reached puberty, ovulation occurs in one of her two ovaries about once every 28 days