List the changes the primary oocyte undergoes in the tertiary follicular stage in the human ovary.

The process of formation of a mature female gamete is called oogenesis. A couple of million oogonia are formed within each fetal ovary. These cells start division and enter into prophase-I of the meiotic division and get temporarily arrested at that stage, called primary oocytes. Each primary oocyte gets surrounded by a layer of granulose and is called primary follicle. The primary follicles are surrounded by more layers of granulose and a new theca and are called secondary follicles.