The Menstrual Cycle

The Menstrual Cycle

What is the menstrual cycle?

The menstrual cycle is one of the defining elements of puberty for girls. It is the release of blood, nutricious lining, and an unfertilized egg cell through the vagina. Those materials are the body’s way of preparing to host a fetus, and when the egg cell goes unfertilized, the materials are shed. The process of shedding and rebuilding is the menstrual cycle.

The cycle starts on the first day of menstruation, when blood and tissues that have built up on the inner lining of the uterus (as if to prepare to host a fetus) break down and flow out of the vagina. Menstruation can last anywhere from 2 to 7 days. The woman’s body then starts releasing hormones that tell the uterus to prepare for a new egg. At about the same time, the hormones are telling the egg to get ready to leave the uterus. The uterus lining become thick with blood and nutrients, in case a sperm were to fertilize the egg. This would give the fertilized egg a nutritious place to grow. This step takes about a week.

What are the components of the “28 day” menstrual cycle?

What is ovulation?

Ovulation is the next step in the process. This is when the egg is released from one of the ovaries and travels down the fallopian tubes. If it is not fertilized by a sperm in the next few days it will begin to dissolve. Most of the time, it isn’t fertilized, so the hormones will tell the blood vessels to cut off the supply as it isn’t needed. The change in supply causes the blood, lining and dissolved egg to begin to exit the vagina as the next cycle begins.

What everyone refers to as the “period” is menstruation, the time when the blood, lining and dissolved egg leave the uterus through the vagina.

What is the "period"?

Pregnancy is most likely to occur during ovulation. This is the time when the egg is traveling through one of the fallopian tubes to the uterus and specifically waits to be fertilized. It is least likely to occur during menstruation, when all the components of a healthy environment for the embryo are leaving the uterus, including the egg that would need to be fertilized in order to get pregnant.

When is pregnancy most likely to occur? When is it least likely?

click on Teens Health to go to an interactive diagram of the menstrual cycle

by Shea Dunlop