Structure and function of the growing follicle

The follicle plays a major role in the dual function of the ovary: oocyte maturation and release; and steroidogenesis required for regulating its own growth and providing the proper environment in reproductive organs for transport of gametes and nidation. Follicles acquire functional competence progressively as they mature following a series of developmental changes. In the present chapter, some aspects of this process and its regulatory factors, as well as some of the manifold functional interactions between the different compartments of the follicle: the oocyte, granulosa and thecal cells are described. The kinetics of ovarian follicular development and responsiveness to gonadotrophic stimulation can best be analysed if followed from the earliest stage onwards. For this reason, an animal model in which this development occurs postnatally, as in the mouse, is more convenient than one in which follicular development is influenced by both maternal and fetal environments, as in the human.