Mature Graafian follicle is generally present in the ovary of a healthy human female around

1. 5-8 day of menstrual cycle

2. 11-17 day of menstrual cycle

3. 18-23 day of menstrual cycle

4. 24-28 day of menstrual cycle  

 
 (b) In humans (female), the menstrual cycle lasts for about 28/29 days. It is the follicular ohase in which the primary follicles in the ovary grow to become a fully mature graafian follicle (due lo FSH stimulation). This phase (follicular) lasts for about 14 days. 
The secretion of gonadotropins (LH and FSH) increases gradually curing this phase and stimulates secretion of estrogen by the growing follicles both LH and FSH attain a peak level in the middle of cycle (about 14th day).
This rapid secretion of LH called LH surge, induces rupture of Graafian follicle and thereby the release of ovum. This ovulatory phase is followed! by the luteal phase during which the remaining follicular cells enlarge lo become the corpus luteum.