Menstruation is when a woman or a girl bleeds from her vagina every month for a few days. It is part of a cycle that prepares her body for having a baby someday.
The cycle has four parts: growing an egg, releasing an egg, waiting for a baby, and shedding the lining.
Each part has a different name and happens at a different time.
- The first part is called the follicular phase. It starts on the first day of bleeding and ends when an egg is released. During this part, the brain tells the ovaries to make a hormone called estrogen. Estrogen helps one or more eggs grow inside small bubbles called follicles. Estrogen also tells the uterus to make a thick layer of blood and tissue called the lining.
- The second part is called the ovulation phase. It is when one of the follicles pops and lets out an egg into a tube called the fallopian tube. This usually happens around the middle of the cycle, but it can be different for each person. The egg can meet a sperm if a man and a woman have sex around this time.
- The third part is called the luteal phase. It starts after the egg is released and ends with bleeding. During this part, the leftover bubble turns into something called the corpus luteum, which makes another hormone called progesterone. Progesterone helps keep the lining in case there is a baby. If there is no baby, the corpus luteum goes away and progesterone goes down.
- The fourth part is called the menstrual phase. It is when the lining comes off from the uterus and goes out through the vagina as blood. This usually lasts for about 2 to 7 days. The menstrual phase is also the start of a new cycle.
Menstruation happens because of changes in hormones, blood vessels, inflammation, and contractions. These are some big words that mean:
- Hormones: These are chemicals that tell different parts of the body what to do. The brain, the ovaries, and the uterus use hormones to control the cycle.
- Blood vessels: These are tubes that carry blood to different parts of the body. The lining has many blood vessels that change during the cycle. They grow bigger when estrogen is high and shrink when progesterone is low.
- Inflammation: This is when the body tries to heal something that is hurt or sick. The lining gets hurt when it loses blood and tissue. The body sends cells and molecules to help it heal.
- Contractions: These are when muscles squeeze and relax. The uterus has muscles that squeeze and relax during menstruation to push out the lining and blood. Sometimes these contractions can cause pain or cramps.
I hope this explanation helps you understand how menstruation works, what parts are involved, and what happens inside the body.
