Study the graph given below and answer the questions that follows .

(i) Name the hormones X and Y.
(ii) Identify the ovarian phases during menstrual cycle.
(a) 5th day to 12th day of the cycle
(b) 14th day of the cycle
(c) 16th day to 25th day of the cycle
(iii) Explain the ovarian events (a), (b) and (c) under the influence of hormones X and Y.

Explanation

(i) Hormone X Luteinising Hormone (LH).
Hormone Y 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 turn 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).
(c) The remaining cells of ovarian follicles are stimulated by the LH to develop corpus luteum. The corpus luteum secretes the large amount of progesterone which is essential for the maintenance of endometrium.