Which of the following event occurs during the ovulation phase ?
The activins and inhibins are glycoproteins that belong to the transforming growth factor -b superfamily. They are secreted from granulose cells. FSH induces steroidogenesis (estradiol production) in granulosa cells in the preovulatory phase (follicular phase). Stimulation of the arrested meiotic division of the ovum occurs at ovulation, till then the oocyte is resting in the prophase of the first meiotic division. This is the reason why the 1st polar body is released along with ovulation. (The second polar body is released after feilisation). Inhibin B has shown increased levels in mid-follicular phase, has a periovular peak, and then declines in luteal phase. Inhibin A is low in follicular phase, reaches a small peak in mid-follicular phase, and increases to reach a peak in luteal phase. Just like inhibin, which is a inhibitory co-molecule of FSH, Activin is also a co-molecule of FSH and is increased when action of FSH is required. i.e. action of FSH is activin mediated. Hence, activin will be highest when the FSH action is maximum in the early follicular phase
Increase in inhibin A level
FSH induce steroidogenesis in granulosa cells in secretory phase
Activin increases
Stimulation of the arrested meiotic division of the ovum
Tests of Ovulation