ABSTRACT
Oogonesis is the process by which the ovarian germ cells mature into eggs to be fertilized. The process occurs through several phases: 1) specifi cation and formation of the primary germ cells (PGCs) in the extraembryonic area and migration of these cells to the ovary; 2) sex differentiation where germ cells are transformed into primary and then secondary oogonia; 3) onset of meiosis where oogonia are now committed to be oocytes; 4) folliculogenesis where diplotene oocytes are recruited to constitute ovarian follicles; 5) intrafollicular growth where the oocyte is under meiotic arrest; 6) vitellogenesis and follicular maturation; 7) ovulation where the oocyte is expelled from its follicle. The end result of oogenesis is PGCs that have attained the competency of forming viable embryos after fertilization.
