Changes

[[Image:Atretic Follicle.jpg|thumb|right|150px|Histological Section of the Ovary showing Characteristics of the Atretic Follicle - Courtesy of J.Bredl, Copyright RVC 2008]]

[[Image:Atretic Follicle.jpg|thumb|right|150px|Histological Section of the Ovary showing Characteristics of the Atretic Follicle - Courtesy of J.Bredl, Copyright RVC 2008]]

* Numerous pyknotic nuclei in the granulosa, absence of mitosis in this layer.  

* Disruption of the basal lamina.

* Presence of free floating cells with dark staining, pyknotic nuclei in the antral cavity.

* Presence of clear vacuoles in the oocyte, disruption of the oolemma.

** Numerous pyknotic nuclei in the granulosa, absence of mitosis in this layer.  

** Disruption of the basal lamina.

** Presence of free floating cells with dark staining, pyknotic nuclei in the antral cavity.

** Presence of clear vacuoles in the oocyte, disruption of the oolemma.

==Function==

==Function==

*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.

*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 [[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.

*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.