Changes

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

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

*The oocyte has developed a thick translucent glycoprotein layer called the Zona Pellucida.

*The [[The_Ovary_-_Oogenesis_-_Anatomy_%26_Physiology|oocyte]] has developed a thick translucent glycoprotein layer called the Zona Pellucida.

*Oocyte surrounded by two or more layers of follicular cuboidal cells. These cells differentiate into the inner Granulosa cells and outer Theca cells.

*[[The_Ovary_-_Oogenesis_-_Anatomy_%26_Physiology|Oocyte]] surrounded by two or more layers of follicular cuboidal cells. These cells differentiate into the inner Granulosa cells and outer Theca cells.

* Connective tissue cells surrounding the granulosa cells differentiate to form the layers of theca cells which produce androgens.

* Connective tissue cells surrounding the granulosa cells differentiate to form the layers of theca cells which produce androgens.

* Theca cells produce Androstienedione which is converted to [[Endocrine_System_-_Ovaries_-_Anatomy_%26_Physiology|17β-Oestrodiol ]](E2) by the Granulosa cell enzyme Aromatase.

* Theca cells produce Androstienedione which is converted to [[Endocrine_System_-_Ovaries_-_Anatomy_%26_Physiology|17β-Oestrodiol ]](E2) by the Granulosa cell enzyme Aromatase.

*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.

*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.

* Despite the presence of the zona pellucida, the inner granulosa cells are able to communicate with the oocyte through gap junctions.

* Despite the presence of the zona pellucida, the inner granulosa cells are able to communicate with the [[The_Ovary_-_Oogenesis_-_Anatomy_%26_Physiology|oocyte]] through gap junctions.

* Following formation of the theca cells, the primary oocyte reaches full size.

* Following formation of the theca cells, the primary oocyte reaches full size.

* Granulosa cells secrete fluid, resulting in the formation of a fluid filled space known as the antrum.

* Granulosa cells secrete fluid, resulting in the formation of a fluid filled space known as the antrum.