Our Menstrual Cycle

(Appropriate for ages 12+)

1.   Menstruation (The Menses Phase)

This phase is what we commonly refer to as our period. A period is the shedding of the lining of the uterus through the vagina. A combination of period blood, mucus and some tissue from your uterus will exist your body through the vagina. Typically your period will last 3-7 days after regularizing, but everyone's cycle is different so this can vary.

2.   The follicular phase

The follicular phase starts on the first day of your menstruation (your period) and will last 13 to 14 days stopping at the start of ovulation, the next phase. Your pituitary gland, also known as the "master gland," which is located in the brain, is in charge of signaling the release of hormones. The pituitary gland will cause the secretion of a follicle* stimulating hormone (FSH) during this time to promote the development of follicles on the surface of your ovaries. Around the 10th day of your cycle, typically a dominant egg will begin to mature form one follicle. This will cause the levels of estrogen* to rise. Another important hormone released is leutinizing hormone (LH) which will help with the maturation of one follicle into an egg. LH will also act as the trigger to start ovulation. During the maturation of an egg you uterus lining will also thicken to prepare for the possibility of pregnancy.

3.   Ovulation (The Ovulatory Phase)

In this phase the egg that is matured* in the previous phase is released from an ovary where it travels along a fallopian tube to enter the uterus. This phase takes a much shorter amount of time; ovulation can last from as little as 16 hours to 24 hours. Ovulation generally only occurs once a month and occurs around two weeks before the start of your next period. The matured egg can be fertilized* by sperm during this time if the sperm reaches the egg in the fallopian tubes. In the case that an egg is fertilized in the fallopian tubes, pregnancy may follow. (There are certain times around and during ovulation where pregnancy is more common. For more information see the page "My Reproductive System" to learn more about your body and its ability to create life)

4.   The luteal phase

The luteal phase proceeds ovulation. In this phase hormones such as progesterone* and small quantities of estrogen* are released from your corpus luteum. The corpus luteum is a group of cells inside your ovaries that will release the previously stated hormones after ovulation. These hormones will lead to the lining of the uterus thickening in order to prepare for the potential of pregnancy. If an egg is fertilized with sperm and attaches itself to the lining of the uterus, then the corpus luteum will continue to release progesterone in order to keep the lining of the uterus in a thickened state. If an egg is not fertilized (if you do not become pregnant) three major things will occur. The first being that the corpus luteum will die, which will cause the second change: progesterone levels will drop. Finally, the the shedding of the uterus lining that begins the menses phase once more. In other words the start of your next period. 

* follicle: a fluid-filled sac that functions as a shell or outer-casing of an immature egg and works towards egg maturation  

* matured/maturation: occurs after an egg has re-entered meiosis for the second time making it now fertilizable 

      - meiosis: the type of cell division in our reproductive organs that divides one cell twice to result in four cells with half as much genetic info, also known as DNA

* fertilized/fertilization: the combining of a male's sperm with a female's egg to form a zygote (which is simply a fertilized egg)

* progesterone: a hormone that prepares the lining of the uterus for the possibility of becoming pregnant

* estrogen: one of the primary sex hormones in women that is necessary for several bodily processes, such as puberty, the menstrual cycle, pregnancy and bone strength