Primordial Follicle

Primordial follicles are the only type of follicle that females are born with. They populate both ovaries, and have the potential to ovulate an oocyte. Females are unable to make more follicles after birth, so the total population of primordial follicles represent all the potential oocytes that a female will have throughout life. Over time, due to ovulation and aging follicles, the number of primordial follicles progressively declines throughout a female’s life.

All primordial follicles have the same structure. They consist of a single primary oocyte surrounded by a single layer of flat shaped follicular cells. They are found clustered throughout the ovarian cortex.

Figure 1: Illustration of primordial follicles inside an ovary.