Changes

*One primary oocyte surrounded by a Single layer of squamous cells known as pre-granulosal cells.

*One primary oocyte surrounded by a Single layer of squamous cells known as pre-granulosal cells.

*Development from the primordial follicle to the primary follicle is characterized by:

*Development from the primordial follicle to the primary follicle is characterized by:

**Increase in the size of the oocyte

**Increase in the size of the [[The_Ovary_-_Oogenesis_-_Anatomy_%26_Physiology|oocyte]]

**The surrounding of the oocyte by a single layer of cuboidal granulosa cells which are capable of hormone production.

**The surrounding of the [[The_Ovary_-_Oogenesis_-_Anatomy_%26_Physiology|oocyte]] by a single layer of cuboidal granulosa cells which are capable of hormone production.

**Separation of the oocyte from the granulosal cells by a thick layer of material known as the zona pellucida.

**Separation of the [[The_Ovary_-_Oogenesis_-_Anatomy_%26_Physiology|oocyte]] from the granulosal cells by a thick layer of material known as the zona pellucida.

* This development is driven by Gdf9 and BMP15. Knockouts of these genes result in the failure of primordial follicles to develop into primary follicles.  These are normally found within the oocyte itself.

* This development is driven by Gdf9 and BMP15. Knockouts of these genes result in the failure of primordial follicles to develop into primary follicles.  These are normally found within the [[The_Ovary_-_Oogenesis_-_Anatomy_%26_Physiology|oocyte]] itself.