Laboratory animals are commonly used for evaluating the physiological properties
of the mammalian ovarian follicle and the enclosed oocyte. The use of different species to
determine the morphological relationship between the follicle and oocyte has led to a recognizable
pattern of follicular stages, but differences in follicle size, oocyte diameter and granulosa cell
proliferation are not consistent across the different species. In an effort to better understand how
these differences are expressed across multiple species, this investigation evaluates oocyte and
follicle diameters and granulosa cell proliferation in the mouse, hamster, pig, and human.