Primary Follicle

Starting at puberty, some of the primordial follicles will be hormonally stimulated to continue growth. The flat shaped follicular cells enlarge into a cube or column shape. Also, the primary oocyte will secrete a sugar protein coating called the zona pellucida that encases the oocyte and separates it from the follicular cells.

A primary follicle consists of:

1. A primary oocyte surrounded by the zona pellucida

2. A single layer of cuboidal or columnar shaped follicular cells.

Figure 1: Illustration of primary follicles inside an ovary.