Physiological factors underlying the formation of ovarian follicular fluid

Abstract

In common with all other cells, the oocyte and granulosa cells are bathed in extracellular fluid. It has, however, become conventional to reserve the term ‘follicular fluid’ for that fraction of the extracellular fluid that accumulates in the antrum of larger follicles. This pool of fluid is of considerable biological significance since its composition indicates the environment in which the oocyte and granulosa cells are growing and maturing. Furthermore, it buffers the internal environment of the follicle against the influence of external conditions presented by the blood stream. The chemical composition of follicular fluid has been studied extensively and found to consist of substances derived from blood as well as from local secretion and metabolism. Particular attention has been paid to the proteins and hormonal steroids. Rather than attempt a comprehensive review, this paper will focus on general physical characteristics of the fluid and the physiological factors that influence its formation. These properties determine the rate at which extracellular fluid is accumulating and, hence, the size and morphogenesis of the Graafian follicle. It is important to reveal the mechanism and dynamics of follicular fluid formation if the composition of the fluid is to be fully understood.