Fig. 1. Classification of follicles in ovarian sections. (A) Note the primordial follicle and single-layered of flat granulosa cells surrounding the primordial oocytes (arrow). (B) Observe the primary follicle and the single-layered cubic granulosa cells around the oocyte (arrowhead). (C) Notice the secondary follicle and the multi-layered cubic granulosa cells neighboring the oocytes (arrowhead) and zona pellucida (arrow). (D) Note the Graafian follicle with C-shaped antrum (star), cumulus oophorous (arrowhead), and stratum granulosum (arrow). Scale bars=50 µm.