So let's summarize the functions of the different hormones involved in the menstrual cycle. And before we begin let's make two important distinctions. Let's divide the menstrual cycle into two phases. So we have the before ovulation, the pre ovulatory phase and we have the after ovulation phase, the post ovulatory phase. And the reason we have to make this decision distinction is because the different hormones involved in the menstrual cycle have slightly different functions in these two phases as we'll see in just a moment. So let's begin in the before ovulation phase.