The Ovarian Cycle + Uterine Cycle = The Menstrual Cycle

Did you know your menstrual cycle consists of not one but two cycles?

The ovarian cycle and the uterine cycle.

Both of these cycles need to be working in tandem harmony in order for the menstrual cycle to exist.

The ovarian cycle involves the ovaries and ovulation. It comprises the follicular phase, ovulation and the luteal phase. During the follicular phase, the brain communicates to the ovaries via the hormone FSH to start developing follicles (fluid filled sacs that each contain an immature egg). A dominant follicle is selected and completes the process of maturation. This dominant follicle produces estrogen. Prior to ovulation, there is an LH surge to trigger the release of the egg from the follicle. Thi follicle then transforms into a temporary endocrine gland called the corpus luteum. This gland produces progesterone that will maintain the rest of the menstrual cycle - the luteal phase. This phase lasts approximately 2 weeks, or continues on during pregnancy. If there is no pregnancy, at the end of the luteal phase progesterone (and estrogen) levels fall and trigger a bleed (period).

The uterine cycle involves the uterus, the endometrial lining and comprises the menstrual, proliferative and secretory phase. During the menstrual phase, the uterine lining (endometrium) is shedding and this is the period. After the period the endometrium enters the proliferative phase where increasing levels of estrogen (correlating with the follicular phase) thicken, plump and rebuild the uterine lining, ready to receive a fertilized egg (or not!). After ovulation, the uterine lining enters the secretory phase. This is the time when a fertilized egg may implant. This is occurring during the luteal phase when progesterone is being released. The endometrium increases its blood supply and mucus secretions and undergoes unique immunological changes in order to be able to receive an embryo and create the optimal environment for it to burrow into the endometrial wall and continue to grow. There is a window of implantation that occurs during the secretory phase where embryo implantation is most optimal.At the end of the secretory phase if there is no pregnancy, the lining breaks down and is released. 

I find we often just think about the ovaries and ovulation when talking about what happens through the menstrual cycle to result in the period, but the uterus is also going through a whole transformation herself each and every cycle, not just during the period!

I find the chemical reactions and changes that happen within the uterine lining during the secretory/luteal phase completely fascinating.

No other part of the human body is designed to allow a “foreign body” to attach itself, embed and continue to grow and flourish.

The immune system within the endometrium is completely unique. Every other part of the body clearly distinguishes “self” from “not self” (a key aspect of a healthy immune system), whereas within the uterus, she orchestrates herself in such a way to allow the “not self” in with open arms and allows her child in. Our first big welcoming embrace from our mamas.

The endometrium doesn’t get enough credit for the miracle and integral aspect to all human life that it is!