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Question
Explain the role of hormones during the menstrual cycle.
Solution
The menstruation phase occurs when the concentration of ovarian and gonadotropin hormones is low in the blood. Reduced concentration of these hormones stimulates the hypothalamus to produce GnRH (gonadotropin-releasing hormone). It activates anterior pituitary to gonadotropin hormones.
(i) Pituitary hormones: The pituitary hormones secreted during the menstrual cycle are FSH and LH. The FSH (Follicular stimulating hormone) stimulates the growth of primary oocyte into the secondary oocyte and the Graafian follicle.
The maximum level of LH (Luteinising hormone) induces the rupture of the Graafian follicle to release ovum containing secondary oocyte (ovulation).
(ii) Ovarian hormones: The FSH secretion by pituitary gland stimulates the ovarian follicles to secrete oestrogen. Oestrogen stimulates the proliferation of endometrium of the uterine wall. After ovulation, the remaining cells of the ovarian follicle are stimulated by LH to develop corpus luteum which secretes a large amount of progesterone. Progesterone is essential for the maintenance of endometrium, for implantation of the fertilised ovum and other events of pregnancy.
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