The menstrual cycle in the normal human female

Abstract

The menstrual cycle is a sequence of morphologic changes in the reproductive system, particularly of the endometrium, that culminate in an episode of uterine bleeding. The cycle may be regarded as consisting of three phases: (a) proliferative (b) secretory (c) decidual or desquamative, but desquamation is more generally included in the proliferative phase. Typical length is twenty-eight days. Clinically, cycle ranges from twenty-five to thirty-one days and this is accepted as normal. It has, however, been found that only 53% of cycles may be expected to fall within this range. The question when exactly in the cycle ovulation does take place is an important one, and will be reviewed briefly after the description of the cyclic changes occuring in genital sites have been fully dealt with.