PRIMARY OOCYTE :-
One cell of the egg nest enlarges and forms the primary oocyte while other forms a layer of follicular epitelium around the primary oocyte.The primary oocyte along with follicular epithelium is known as primary follicle.
SECONDARY OOCYTE :-
It is also known as secondary follicle because primary follicle changes into secondary foliicle when surrounded by several layers of granulosa cells and a new theca.