How Ovulation Happens

To really understand ovulation and the menstrual cycle—and especially to understand irregularities or changes to the cycle—it's important to know the events that result in normal cyclic function. Let's start with some facts and definitions. They'll help you learn more about the process, and will give you the common language and vocabulary to discuss it with your doctor, friends, or even women's health message boards.

Day 1: the first day of normal flow of the menstrual period. In an idealized 28-day menstrual cycle, ovulation occurs on day 14.

Follicular Phase: the phase of the menstrual cycle beginning on day one and continuing until the time of ovulation.

Proliferative Phase: describes the development of the lining of the uterus. It occurs during, and is synchronous with, the follicular phase.

Luteal Phase: the phase of the cycle beginning at the time of ovulation and continuing until the next menses begin.

Secretory Phase: describes the changes that occur in the lining of the uterus after ovulation. It occurs during, and is synchronous with, the luteal phase.

Follicle: the fluid-filled sac that contains the developing egg and the cells surrounding that sac.

Estradiol: the primary estrogen produced by the developing follicle.

Corpus Luteum: after release of the egg, the follicle becomes the corpus luteum and begins to produce progesterone.

Progesterone: the principal hormone produced by the corpus luteum.