What Happens During Our Menstrual Cycle?

Every woman is born differently. We have different personalities, different characteristics and body types. The same goes for every woman’s menstrual cycle. The “time of the month” can be every other month for some women, or very regular. Your period can be heavy and painful, filled with cramps and bloating, but you will always have that one friend that says they can “barely even feel it.” No matter how lucky or unlucky we get when it comes to how our bodies react to our periods, it can be helpful to understand each phase of the cycle in order to be more in tune with ourselves. Some phases overlap each other because, lets face it, women are excellent multitaskers.

Phase 1: Menstruation

Many women are misled to think that the days we “see” our period is the only part of our menstrual cycle. Actually, this 3-7 day span of time is only the first part of the entire cycle. Menstruation is when the endometrium (the thick lining inside the uterus) starts to shed and is eliminated from the body along with blood and mucus.

Phase 2: Follicular Phase

At the beginning of the menstruation phase, estrogen is very low so our pituitary gland releases two hormones called follicle-stimulating hormone and luteinizing hormone, which incites the ovary to generate tiny follicles (5-20 typically) that each carry an egg. These follicles resemble small cysts and anchor themselves on the surface of the ovary.  It is important to note that when women are born, their ovaries already have millions of eggs; therefore no new eggs will ever be developed. The eggs only surface during this follicular phase. Usually, one follicle housing an egg will start to grow faster than the other follicles. When this happens, (usually around the 10th day of the cycle) estrogen levels will begin to increase, the follicle-stimulating hormone starts to decrease and the other follicles will die off, leaving the one follicle to mature to an egg. This phase does not end until the next phase, ovulation, is complete.

Phase 3: Ovulation

Around day 12-14 of the menstrual cycle, the mature egg will be released from its follicle because of high levels of the luteinizing hormone. The egg travels through the fallopian tube with the help of small “hairs” called cilia. Once the egg enters the uterus, it has around a day to be fertilized by sperm. The follicle on the ovary that once housed this egg will begin to transform into the corpus luteum. At this point, the follicular phase is completed, but the ovulation stage encompasses the next one, the luteal phase.

Phase 4: Luteal Phase

The luteal phase begins with the fertilized egg. A fertilized egg does not mean it will necessarily result in a pregnancy. The corpus luteum, which was previously the follicle, triggers an increase in progesterone, making the uterus a prime environment for the fertilized egg. If pregnancy happens, the embryo implants itself and then the embryonic process of gestation begins. If not, the progesterone levels will decrease and the lining of the uterus will start to shed, starting the menstruation process again.

References

Menstrual cycle. (2019). Betterhealth.vic.gov.au. Retrieved 17 April 2019, from https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/menstrual-cycle.

Sohda, S., Suzuki, K., & Igari, I. (2017). Relationship Between the Menstrual Cycle and Timing of Ovulation Revealed by New Protocols: Analysis of Data from a Self-Tracking Health App. Journal Of Medical Internet Research19(11), e391. doi:10.2196/jmir.7468

The Menstrual Cycle. (2019). UCSF Medical Center. Retrieved 17 April 2019, from https://www.ucsfhealth.org/education/the_menstrual_cycle/