Changes

*Theca cells become organised into Theca Interna and Theca Externa layers. The Theca Interna layer cells differenciate into steroidogenic cells produce the Androgen Androsteinedione in response to the Gonadotrophin Luteinising hormone (LH).

*Theca cells become organised into Theca Interna and Theca Externa layers. The Theca Interna layer cells differenciate into steroidogenic cells produce the Androgen Androsteinedione in response to the Gonadotrophin Luteinising hormone (LH).

*Theca Cell layer becomes vascularised.

*Theca Cell layer becomes vascularised.

*Granulosa cells become responsive to Follicle Stimulating Hormone (FSH) and start producing 17β-Oestrodiol and small amounts of Inhibin and Progesterone.

*Granulosa cells become responsive to Follicle Stimulating Hormone (FSH) and start producing [[Endocrine_System_-_Ovaries_-_Anatomy_%26_Physiology|17β-Oestrodiol]] and small amounts of Inhibin and Progesterone.

'''Dominant Follicle'''

'''Dominant Follicle'''

*Only a single Dominant follicle forms with each wave of folliculogenesis.

*Only a single Dominant follicle forms with each wave of folliculogenesis.

==function==

==function==

*Follicular cells produce hormones important for the progression of the oestrus cycle. Theca cells produce Androstienedione which is converted to 17β-Oestrodiol (E2) by the Granulosa cell enzyme Aromatase. At low levels E2 acts to negatively feedback to the hypothalamus and pituitary gland, inhibiting production of Gonadotrophin releasing Hormone (GnRH) and LH + FSH respectively. When the E2 level increases above the level of threshold it acts to stimulate gonadotrophin release. This results in the LH surge responsible for Ovulation.

*Follicular cells produce hormones important for the progression of the oestrus cycle. Theca cells produce Androstienedione which is converted to [[Endocrine_System_-_Ovaries_-_Anatomy_%26_Physiology|17β-Oestrodiol ]](E2) by the Granulosa cell enzyme Aromatase. At low levels E2 acts to negatively feedback to the hypothalamus and pituitary gland, inhibiting production of Gonadotrophin releasing Hormone (GnRH) and LH + FSH respectively. When the E2 level increases above the level of threshold it acts to stimulate gonadotrophin release. This results in the LH surge responsible for Ovulation.

*The positive feedback action of E2 leading to a surge in LH only and not FSH is due to the selective action of Inhibin. Inhibin is a hormone produced by granulosa cells that selectively inhibits FSH production by the pituitary gland.

*The positive feedback action of E2 leading to a surge in LH only and not FSH is due to the selective action of [[Endocrine_System_-_Ovaries_-_Anatomy_%26_Physiology|Inhibin]]. [[Endocrine_System_-_Ovaries_-_Anatomy_%26_Physiology|Inhibin]] is a hormone produced by granulosa cells that selectively inhibits FSH production by the pituitary gland.