Menstrual Cycle: Basics

The menstrual cycle affects females all over the world. Although something that happens specifically to women, men, too, should be well acquainted with the fundamentals as it takes two people to procreate. Unfortunately, many (both men and women) are not familiar with the basics of the menstrual cycle. To understand menstruation (menses), we will first go over the female reproductive system.

The Female Reproductive System - Anatomy & Physiology

The female reproductive system includes the internal (ovaries, fallopian (uterine) tubes, and the uterus) and external (genitals) organs that are located in the pelvic region. (1)  

The ovaries are organs which are in charge of storing, developing, and releasing the eggs. (2)

They go through a constant process of depletion in which most eggs die without getting to the maturity stage.  

The uterus is the organ that receives the fertilized egg and supports the growth of the embryo. This is where the baby develops.

‍Fallopian tubes connect the ovaries to the uterus. The cervix is part of the uterus that produces secretions (discharge) and acts as a passage for sperm (male gamete). (3)

Last but not least, the vagina allows for the blood to come out during menstruation, holds the sperm, and allows for childbirth to happen.

In order for the menstrual cycle to happen, both the endocrine system (hormones) and the reproductive system have to work together.

Menstrual Cycle

Hormones play a crucial role in the menstrual cycle. The hypothalamus (located in the brain) produces GnRH (gonadotropin-releasing hormone) that stimulates the pituitary gland to produce the follicle-stimulating hormone (FSH), which is responsible for developing an egg. During this time, FSH also causes estrogen levels to rise. During the maturation phase of the egg, the luteinizing hormone (LH) together with FSH causes the release of the eggs to happen - a process known as ovulation. (4) The hormone progesterone makes sure the uterus is ready to receive an egg (embryo). The sperm travels through the fallopian tubes, and if the egg is fertilized, pregnancy occurs. However, if the egg is not fertilized, the lining of the uterus (endometrium) begins to shed and menstruation occurs. (4) The shedding of the uterus occurs every 28 days (approximately).

Phases

There are four phases of the menstrual cycle:

1. Menstrual phase
2. Follicular phase
3. Ovulation phase
4. Luteal phase

Menstrual Phase

The menstrual cycle lasts around 28 days on average. The menstrual phase of the cycle begins on your first day of bleeding and lasts for about 5 days (approximately). During this phase, the lining of the uterus (endometrium) is shedding and the menstrual fluid (blood, cells, and mucus) is eliminated. (5) Because our bodies are trying to get rid of the menstrual fluid, many women experience abdominal cramps during this phase. (6) When we say “I got my period” this is the phase we are talking about.

Follicular phase

The follicular phase begins on the first day of bleeding and it ends with ovulation (lasts 16 days on average). (7) In this phase, the follicle-stimulating hormone (FSH) stimulates the ovary to produce the follicles (sacs) that contain immature eggs. Every follicle stores one egg. The growth of follicles and their maturation is what helps with the thickening of the uterus and the preparation for pregnancy. (7)

Ovulation phase

As we stated before, ovulation happens when a mature egg is released from the surface of the ovary. (5) The ovulation phase lasts about 24 hours, making it the shortest phase of the cycle. (7) According to Johns Hopkins Medicine, ovulation happens 12-14 days prior to the start of the cycle. The fertile window, or the period when your chances of getting pregnant are the highest, lasts about 7 days. It begins 5 days before ovulation and includes the day of ovulation and the day after. (8) Understanding the menstrual cycle and knowing about ovulation can increase your chance of getting pregnant.

Luteal phase

The premenstrual phase is the luteal phase. This phase is associated with the Premenstrual Syndrome (PMS) and it begins on day 15 and ends on day 28 (approximately). (9) During the luteal phase, the lining of the uterus thickens - making it ready for pregnancy.  However, when the fertilization does not happen, estrogen and progesterone levels drop, and your period starts. If you are feeling fatigued and if you are experiencing anxiety, you might be in the luteal phase of your menstrual cycle.  

Fertility

The important thing to note is that the above information applies to women who have regular periods. It would be inaccurate to say that there is a “one-size-fits-all” rule when it comes to the menstrual cycle. Depending on your cycle's regularity and length, your fertility window might differ from your friend’s. Keeping track of your cycle is very important and one of the ways to do it is by monitoring your vaginal discharge.

Vaginal Discharge

As you go through the menstrual cycle phases and as your hormone levels rise and drop, you might notice some changes in your vaginal discharge (mucus). Your vaginal discharge can tell you a lot about your cycle. The mucus pattern chart can be accessed here (https://www.plannedparenthood.org/uploads/filer_public_thumbnails/filer_public/64/cd/64cd083d-916e-44f1-ba7b-2ac6c1edccd5/ppol-mucuschart-092015_r2_1.png__1200x900_q75_subsampling-2.jpg).

• DURING PERIOD - no mucus due to blood; UNSAFE days
• AFTER PERIOD - you might have a couple of dry days (3-4) where there is no mucus; might be SAFE
• BEFORE OVULATION - yellow, cloudy, sticky mucus; LESS SAFE days
• DURING OVULATION - stretchy, slippery with a consistency of raw egg whites; UNSAFE days
• AFTER OVULATION - you might see less mucus, and it might be cloudy and sticky; SAFE days