Human follicle development

Schematic representation of human follicle development during the follicular phase of the menstrual cycle. There are two major events in this process: increased sensitivity of a maturing follicle and selection of a single dominant follicle. In spontaneous cycles, this is achieved at the beginning of the cycle by a transient increase in serum FSH concentrations above some threshold value; the concentrations then decrease, preventing more than one follicle from undergoing preovulatory development.