(i) Hormone ‘X’ is Luteinising Hormone (LH) and ‘Y’ is Follicle Stimulating Hormone (FSH).
(ii) (a) Follicular phase (proliferative phase).
(b) Ovulatory phase (release of ovum) followed by luteal phase.
(c) Luteal phase.
(iii) (a) FSH is secreted by the anterior pituitary, which
stimulates the ovarian follicle to secrete oestrogen, which in mm stimulates the proliferation of the endometrium of the uterine wall.
(b) Both LH and FSH attain a peak level in the middle of cycle (about 14th day). Rapid secretion of LH leading to its maximum level during the mid-cycle is called LH surge. It induces rupture of Graafian follicle and thereby the release of ovum (ovulation).
Due to these events, this phase is termed as evulatory
phase of menstruate cycle.
(c) The remaining cells of ovarian follicles are stimulated by the LH to develop corpus luteum. The corpus luteum secretes large amount of progesterone, which is essential for the maintenance of endometrium. This is known as luteral phase.