In the preceding chapters, the sexual differentiation of the gonads, functional characteristics of the gametes and reproductive activation at puberty were discussed. This chapter describes the mature ovary and control of the menstrual cycle. The 1980s was an exciting decade with major advances in understanding in this area following the discovery of the neuroendrocrine nature of the ovary. The ovary not only produces steroids but also a number of other hormones, regulatory peptides and growth factors. Some of these, like inhibin, have extra ovarian functions, whereas others, like oxytocin and relaxin, exert their function within the ovary. A number of cytokines (immune hormones) and growth factors, like epidermal growth factor (EGF), fibroblast growth factor (FGF) and insulin-like growth factor (IGF), regulate ovarian function from within by modulatory effects on immunity, steroidogenesis and connective tissue remodelling of differentiating cell types. Most importantly, at all times information regarding the ovarian condition is conveyed to the CNS by autonomic nerve fibres with which the ovary is intensely innervated. Such functional inter-relatedness can lead, at times of stress, to confusing symptoms when the causative factors may remain obscure. For example, in patients with nutritional defects, infertility caused by hypothalamic and ovarian disturbances may occur in seemingly healthy persons (Chapter 18).

In functional terms, the menstrual cycle can be viewed as the integration of three fundamental activities controlling fertility. These functions are the control of the ovarian cycle (maturation and release of the oocyte), the uterine cycle (provision of a suitable environment for the blastocyst to implant) and the cervical cycle (selective sperm entry into the female reproductive tract only during the periovulatory period).