An illustration for "embryo tales" stories, that features an embryo, sperm, follicles, and a uterus

Menstruation Matters

Written by: Emily Santora
Illustrated by: Sabine Deviche

show/hide words to know

Embryo: the egg after fertilization and before it has developed into a recognizable form.

Endocrine gland: a part of the body that makes and releases hormones.

Endometrium: tissue that lines the inside of the uterus. The endometrium sheds each month during a period.

Hormone: a chemical message released by cells into the body that affects other cells in the body.

Period: the shedding of the inside of the uterus, which normally happens about once a month and lasts five to seven days. Periods usually start around age twelve to fifteen and are also called menstruation.

Representation: when a certain group of people participates in decision-making, is seen, and respected by peers in a specific space. This is most important in politics and the media.

Uterus: or womb is a major female reproductive sex organ of most mammals including humans. It is within the uterus that the fetus develops... more

Zygote: also known as a fertilized egg. The single cell that results after sperm and egg fuse together...more

When was the last time that you saw the doctor? She probably checked your vital signs, like your temperature and blood pressure. Those are both measures of health. Another measure of health for many women is a period, or menstruation.

A woman's pregnant belly

The menstrual cycle prepares the body for pregnancy. Image by Towle Neu via Wikimedia Commons.

A period is a sign that a person’s menstrual cycle is working properly. The menstrual cycle prepares the body for pregnancy. Usually girls and women have menstrual cycles. But, anyone with a uterus and ovaries can experience it each month. During that cycle, levels of hormones in the body rise and fall. Those changes help thicken the endometrium and help eggs to mature.

A mature egg leaves an ovary and travels through the fallopian tube, where it can combine with a sperm cell to become a zygote. The zygote divides more and arrives inside the uterus. There, it implants onto the thick endometrium and grows into an embryo. That’s where the embryo gets nutrients during pregnancy. 

But the menstrual cycle rarely ends in pregnancy. A period happens when an embryo does not form, so the body does not need the thick endometrium. Instead, it sheds and leaves the uterus through the vagina. This is called menstrual bleeding. Wait… bleeding? That sounds scary. Actually, regular menstrual bleeding is healthy. Let’s learn more about what periods are and why they happen. 

It's All in the Ovaries

A lot of people go to the doctor regularly. Periods also tend to happen on a regular basis. That’s because they’re part of a cycle called the menstrual cycle.

Periods happen at the start of the menstrual cycle and usually last five to seven days. A new menstrual cycle begins about every twenty-eight days. Some people have shorter menstrual cycles, others have longer ones. But generally, they happen around once a month.

Close up of ovary illustration showing egg or follicle development

Twenty-eight days is often the length of a full menstrual cycle. Click for more detail.

Typically, girls begin having periods around twelve to fifteen years old. Periods are an important, normal change that lets people know that their bodies are functioning in a healthy way. But periods can also reveal a lot about a person’s overall health. If someone exercises too much, eats too little, or is very stressed, their periods can disappear.

Typically, females stop having periods when they are around fifty years old. Near that age, the female body usually experiences menopause. That is a stage when the ovaries stop creating estrogen. 

Body Talk

One hormone that is made in the ovaries is estrogen, and another one is progesterone. The ovaries make varied amounts of those hormones throughout a woman’s life. The levels of those hormones help control the menstrual cycle and cause its side effects.

For example, at the start of the menstrual cycle, there is very little estrogen, which tells the thick endometrium to shed. That’s when a period starts. Changes in hormone levels can also cause acne, bloating, headaches, and mood changes. These effects are called premenstrual syndrome and may happen during the days that lead up to periods.

A person may also have cramps when they are menstruating. Have you ever had a stomachache and felt that unpleasant, twisting pain? That’s what menstrual cramps can feel like. Some people have worse cramps than others. Painful cramps can make someone feel so poorly that they stay home from school or work.

Taking Control of the Menstrual Cycle

Has your doctor ever recommended that you take vitamins to stay healthy? Similar to daily vitamins, some people may take pills to control their menstrual cycles. That may be a solution if their periods are too painful, too heavy, or too unpredictable.

Birth control pills

Many women use birth control pills to make their periods lighter, or control the timing of periods. Image by BruceBlaus via Wikimedia Commons.

Those are birth control pills, and they usually consist of hormones like estrogen that scientists make in a lab. They put those hormones into different birth control pills. Some birth control pills only have estrogen or progesterone, while others have both. But, the pills may also cause some people to have nausea, mood changes, and weight gain. So, it is important for a person to decide which birth control is the best for their body.

Products for Periods

There are different products that can absorb or collect menstrual blood. Those include, but are not limited to, sanitary pads, tampons, and menstrual cups. Sanitary pads stick to the inside of underwear and absorb menstrual blood. Tampons also absorb menstrual blood but you have to insert them into the vagina. Menstrual cups are a newer and more sustainable way to collect menstrual blood, because you can reuse them. You can insert a menstrual cup into the vagina like a tampon, but it collects menstrual blood inside the cup rather than absorbing it.

Three different period products for menstruation - a cup, a pad, and a tampon

Here are three of the major products that people use to collect menstrual blood during their periods. Click for more detail.

It seems like we know a lot about what happens during periods and how to manage them. But was it always like that? Over time, people experimented and learned more about what happens during the menstrual cycle.

Menstruation In History

Periods are not a new thing. The female body has worked in mostly the same way and people have experienced periods since the beginning of human life. Ancient Greek philosopher Hippocrates wrote about periods way back in 400 BCE. As a cure for especially painful periods, he recommended that people become pregnant more often.

A drawing of a sanitary belt from 1905

Over the years, our understanding of menstruation has changed. So have the products that we use to capture menstrual blood. In the early 1900s, some women would wrap cotton in cheesecloth and attach it to a sanitary belt under their skirts.

Later, Aristotle, another ancient Greek philosopher, even wrote about periods. One of Aristotle’s teachings was that everything has order, including periods. For that reason, he guessed that people who did not have regular periods might have trouble getting pregnant.

Hypothesizing About Hormones

It was not until much later, in 1953, that doctor Katharina Dorthea Dalton explained an important part of periods: premenstrual syndrome. At that time, Dalton noticed that many of her patients had acne, bloating, headaches, and mood changes before their periods. Today, we know those to be symptoms of PMS, or premenstrual syndrome.

Dalton guessed that low amounts of one female hormone, called progesterone, worsened symptoms of PMS. To test her hypothesis, Dalton treated her patients with a unique type of that hormone. If Dalton’s theory was correct, then progesterone would ease her patients’ symptoms. It turned out that it did. Dalton later coined the term PMS to describe her patients’ symptoms. Dalton’s experiment show us how changing amounts of hormones affect the body during the days that lead up to periods.

Menstruation Matters

After Dalton defined premenstrual syndrome, others wrote books to teach people about periods. That information spread in the 1900s when women’s movements emerged. At that time, women fought for equality and representation. One group that did so in the US was the Boston Women’s Health Book Collective. That organization started in the 1960s to teach people about reproductive health. That included teaching about periods.


Menstrupedia helps teach young women about their periods.

Today, efforts to educate people about periods continue. In 2014, activist Aditi Gupta published a comic book, called Menstrupedia Comic: The Friendly Guide to Periods for Girls, to teach people in India about periods. The comic book also teaches that periods are normal and nothing to be ashamed of. Lots of people assume periods are gross, but others try to correct those negative ideas. This helps make sure that everyone feels safe and comfortable taking care of their bodies.

This Embryo Tale was edited by Risa Schnebly and is based on the following Embryo Project articles:

Horwitz, Rainey. “Boston Women’s Health Book Collective, later Our Bodies Ourselves (1969–).” Embryo Project Encylopedia (2019-09-06). ISSN: 1940-5030

Santora, Emily. “Menstrupedia Comic: The Friendly Guide to Periods for Girls (2014), by Aditi Gupta, Tuhin Paul, and Rajat Mittal.” Embryo Project Encylopedia (2020-06-16). ISSN: 1940-5030

Van Iten, Brendan. “Estrogen and the Menstrual Cycle in Humans.” Embryo Project Encyclopedia (2016-06-22). ISSN: 1940-5030

Zietal, Bianca. “Katharina Dorothea Dalton (1916–2004).” Embryo Project Encylopedia (2017-05-24). ISSN: 1940-5030

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Bibliographic details:

  • Article: Menstruation Matters
  • Author(s): Emily Santora
  • Publisher: Arizona State University School of Life Sciences Ask A Biologist
  • Site name: ASU - Ask A Biologist
  • Date published: August 28, 2021
  • Date accessed: June 12, 2024
  • Link:

APA Style

Emily Santora. (2021, August 28). Menstruation Matters. ASU - Ask A Biologist. Retrieved June 12, 2024 from

American Psychological Association. For more info, see

Chicago Manual of Style

Emily Santora. "Menstruation Matters". ASU - Ask A Biologist. 28 August, 2021.

MLA 2017 Style

Emily Santora. "Menstruation Matters". ASU - Ask A Biologist. 28 Aug 2021. ASU - Ask A Biologist, Web. 12 Jun 2024.

Modern Language Association, 7th Ed. For more info, see
Art piece Menstruate with Pride by Sarah Maple; a variety of people all look at one woman who has a blood stain from her period on her white dress.

Why is talking about periods something that makes some people uncomfortable? Artist Sarah Maple's art piece "Menstruate with Pride" carries her message about how some women feel about periods.

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