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Follicles - Anatomy & Physiology (view source)
Revision as of 14:02, 9 September 2008
, 14:02, 9 September 2008→Endocrine Control of Follicular Growth and Steroidogenesis
== Endocrine Control of Follicular Growth and Steroidogenesis ==
== Endocrine Control of Follicular Growth and Steroidogenesis ==
* Under gonadotrophin stimulation, the Antral follicle starts to grow.
* Initially, FSH acts on granulosa cells to induce synthesis of oestrogens.
* Oestrogen has a paracrine action within the ovary to induce the proliferation of granulosa cells.
* During early-mid follicular phase of the oestrous cycle, plasma oestrogen exerts a negative feedback inhibition on gonadotrophin secretion.
* As a result of this, FSH levels begin to fall.
* The inhibiting effect of oestrogen only occurs whilst plasma oestrogen is below a certain threshold value.
* During later stages of the follicular phase of the oestrous cycle, one follicle willl become dominant and it becomes the major producer of oestrogen.
* Under the influence of oestrogen, granulosa cells which were previously unresponsive to LH, acquire LH-receptors and become responsive to LH.
* The plasma concentration of oestrogen starts to rise.
* When plasma concentrations rise above the threshold value, it acts to enhance gonadotrophin secretion by positive feedback.
* The high level of oestrogen causes the LH surge that leads to ovulation.