Question

Ovulation is triggered primarily by:

a.Decreasing levels of FSH

b.Increasing levels of HcG

c.Decreasing levels of estrogen and progesterone

d.Increasing levels of progesterone

e.A surge of LH occurring mid-cycle

Answer 1

Ans (e) a surge of LH occuring mid -cycle

Ovulation is primarily triggered by the surge of LH hormone occuring mid mentrual cycle. The LH hormone is a gonadotropin , secreted & synthesized by pituatiary gland in response to GnRH secreted by hypothalamus, which is responsible for triggering the synthesis of FSH & LH from anterior pituitary.

- The FSH hormone is respnosible for developement & maturation of immature oocyte into mature Graafian follicle before ovulation. The increased levels of FSH causes maturation of follicles before ovulation.

- As the mature Graafian follicle is formed by the increased levels of FSH & now it is ready to release ovum , the process called ovulation, which is marked by the very high levels of LH hormone or LH surge & stimulating the release of ovum from the follicle. The process of ovulation occurs during the middle days of complete menstrual cycle.

- The pre - ovulatory LH surge has following key functions :

* triggering of ovulation

* Disruption of cumulus -oocyte complex

* Luteinization of granulosa cells

* induction of resumption of oocyte meiotic maturation.

As the follicle ruptures, it laters gets converted into corpus luteum which secretes progesterone & its level increases & the level of LH hormone decreases as the process of ovulation is completed for which LH hormone is responsible.

Hope this will help you?