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Menstrual Cycle in Humans

When a girl is between the ages of 11 and 14, her body enters puberty and begins to change. Her breasts begin to grow, her hormones change and her body begins a menstrual cycle in preparation for pregnancy. This cycle is famously cited as lasting 28 days, but can last for as little as 21 days or as long as 50, depending upon the individual and any factors that may disrupt it, such as hormonal imbalances or stress.

  1. Phase 1 - Menstrual Period

    • Menstrual cycles are counted from the first day of bleeding--commonly known as your period--up until the first day of your next period. Menstrual bleeding usually lasts from four to six days, and can vary in intensity from a light to heavy flow, sometimes with clotting. This bleeding is the shedding of the endometrium--the thickened lining of your uterus--readying it for another cycle.

    Phase 2 - Follicular Phase

    • Once the uterus has been cleaned out, your period ends and a new, healthy lining begins to grow. At the same time, one of your ovaries prepares to release an egg from its follicle. The time necessary to properly mature an egg can vary, and it is this phase that dictates how long or short your cycle will be. The end of your follicular phase is the buildup to the egg release, also known as ovulation. These few days--usually only about three to five days--are when you are most fertile.

    Phase 3 - Luteal Phase

    • This is the last phase of your menstrual cycle, and begins on the day you ovulate. Contrary to popular belief, not every woman ovulates precisely in the middle of her cycle but can release an egg from as early as day seven and as late as day 39, or even later depending on the circumstances. This phase continues until the first day of your next period, and typically remains pretty constant and predictable in length, usually lasting for about two weeks.

    Premenstrual Syndrome (PMS)

    • If you're not paying attention to your cycles, you may have an inkling about when your period is about to begin, judging from certain emotional and physical symptoms you experience right before it arrives. PMS affects about three out of every four women, with the most common symptoms being moodiness, irritability and food cravings. The good news is these symptoms only appear a few days before your period and dissipate once the bleeding begins.

    Disorders

    • There are numerous menstrual cycle disorders that can affect not only your daily life, but also your fertility if left untreated. One in five women experience abnormal uterine bleeding, in which their periods are so heavy it affects their normal activities. Some women have no periods at all, which is called amenorrhea, and is usually due to hormonal imbalances or thyroid problems. If your periods are irregular or hinder your ability to go about your daily life, see your doctor.

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