Anatomy and physiology

What is a female period cycle? Get facts about your menstrual periods

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What is a female period cycle! The question is so simple which comes into every girl’s mind. 

Do you know? 

A female has 450 menses throughout her life. It means your body prepares for pregnancy 450 times which happens every month till menopause. 

Despite this, infertility is being a very noticeable issue in our society. The infertility problem is due to a lack of awareness about menstruation and sex education in many countries like India or Muslim countries. But if you see the western countries, they frequently provide education on sex

Generally, many females (or males) don’t have a complete understanding of a female’s reproductive system. Even they don’t know what actually happens during the female period cycle and why it comes every month. 

Here, I want to clarify this mysterious or most confusing menstrual cycle process. 

This information will help you either get pregnant or avoid pregnancy. In this article, we will learn – 

  • what is a female period cycle?
  • how period occurs in female?
  • why is menstruation important for a female?


I’ll help you answer all these questions in this post. So, without further delay, let’s start this fastidious topic. 


What is a female period cycle? Why is the menstrual cycle called a cycle?

A female period is just the first phase of your menstrual cycle.

During this phase, you may have normal bleeding and unwanted tissue release from the uterus every month. Usually, it happens for up to 5 days. This monthly process is called “period” or “menstrual phase” or “menses” or “menstruation.” The period indicates your egg is not fertilized with sperm. 

What is a female period

As far as the concern of the menstrual cycle, it is a series of events that naturally occurs every 28 days throughout the childbearing period. In other words, if an egg is produced cyclically every 28 days, that is called the menstrual cycle.

There are two primary cycles involved in your menstrual cycle – the uterine cycle and the ovarian cycle. During this menstrual cycle, some structural and functional changes may occur in your ovary and uterus. These changes can make your pregnancy possible. 

Moreover, the brain has a significant role in controlling your menstrual cycle. It produces crucial hormones from the hypothalamus by the anterior pituitary. These organs work together and communicate through hormones to keep your menstrual process let it going well. 


What happens to your body on your period?

The start of menstruation is a sign that a girl is able to get pregnant. In a female period, you may get blood from your vagina, which is a primary sign of menstruation. 

Apart from this, some symptoms may discomfort you and interfere with your day-to-day activities.  

You may have following periods symptoms before pregnancy – 

  • Lower back pain
  • Abdominal cramps
  • Bloating
  • Irritability
  • Mood swings
  • Fatigue or low energy 
  • Breast soreness (or breast pain)
  • Acne 


How does menstrual cycle happen?

To better understand how period occurs in females, it is important to learn four phases of menstrual cycle – follicular phase, ovulation phase, luteal phase, and menstrual phase.

What is a female period

Let’s discuss each step thoroughly – 

Day 1 to 14 – Follicular phase (in the ovary)

When a female gets a period. It would consider the first day. Simultaneously, your ovary prepares eggs for the next cycle. 

The follicular phase is the first phase of your menstrual cycle, occurring in both ovaries. Whenever a female is born, she gets a special type of stem cell is called oogonium

Generally, the story begins when you hit puberty. When you get sexually mature at age 12 to 14 (menarche). The oogonium forms the primordial follicle. Every month, the primordial follicle automatically starts to grow. 

The primordial follicle contains an immature ovum (oocyte) surrounded by flattened epithelium cells. After some days, the primordial follicle converts into a primary follicle. 

In this primary follicle, flattened epithelium cells become cuboidal cells. These cuboidal cells provide nutrition to the ovum

Here, your brain has a crucial role in the secretion of hormones. Your brain secretes FSH (follicle-stimulating hormone) from the hypothalamus by the anterior pituitary. This hormone helps in the maturation of follicles. 

Under the influence of FSH, the primary follicle converts into a secondary follicle. 

In this secondary follicle, the ovum gets a thick transparent membrane of zona pellucida. The primary function of zona pellucida is to allow only human sperm. However, it also allows only 1 sperm out of millions of sperm. 

Moreover, the ovum and zona pellucida are associated with a layer of granulosa cells

Then secondary follicle is finally surrounded by theca cell. 

Here, the Theca cell has a vital role in producing androgen (male sex hormone). This androgen moves inside the granulosa cells and converts androgen into estrogen (female sex hormone) by the aromatase enzyme.

This estrogen goes to the uterus, which helps in the proliferation of the uterus wall. In addition, it sends a signal to the hypothalamus to stop FSH release. 

Eventually, this secondary follicle converts into a Graafian follicle. It contains a fluid-filled cavity, especially in granulosa cells. Now, it becomes a fully mature follicle that is ready for ovulation. 

The Graafian follicle release the inhibin B hormone, which stops the secretion of FSH.  

The Graafian follicle is a mature follicle that contains – 

Ovum (center) + zona pellucida + granulosa cell (inside the fluid-filled cavity) + theca cell (outer layer)

What is a female period

Day 6 to 14 – Proliferative phase (in the uterus)

As soon as your period is over, the uterus grows for the next cycle. Generally, the uterus has three main layers – endometrium (innermost layer), myometrium (middle layer), and perimetrium (outer layer). 

The endometrium comprises stratum functionalis (superficial layer of the uterine cavity) and stratum basalis (deep layer).

Stratum functionalis (S. functionalis) contains spiral coiled arteries, whereas stratum basalis (S. Basalis) has straight arteries. 

In this phase, estrogen signals the endometrium layer for regeneration. Then, the S.functionalis layer multiplies and makes the endometrium layer thick. 


Day 14 – Ovulation (in the ovary)

Ovulation is a process when the dominant follicle releases a mature egg from the ovary on the 14th day. During this phase, a high amount of LH (Luteinising hormone) is released from your brain is called LH surge

Your LH just releases a few hours before ovulation. LH hormone stimulates due to a high level of estrogen. Under the influence of LH, mature Graafian follicles become ruptured. Then, this follicle reaches the wall of the ovary.

The LH helps increase pressure inside the fluid-filled cavity and makes the outer layer avascular stigma (necrosis). Due to this necrosis, exocytosis occurs, and the mature ovum is released from the ovary. 

Ovum comes out with an outer covering of granulosa cells. These granulosa cells act as a bodyguard of the ovum. It is also called corona radiata of the ovum

After that, this ovum goes to the fallopian tube. If the ovum gets sperm, then pregnancy occurs. 

If you didn’t have sexual intercourse during this period. Then pregnancy does not take place. 

Normally, the life span of an ovum is 48 hours. If the ovum does not interact with sperm, then apoptosis takes place. In other words, the ovum dies in the fallopian tube by macrophages and neutrophils. 

Here, the story is not finished yet. 


Day 15 to 28 – Luteal or Secretory phase

Just after ovulation, the remaining part of the Graafian follicles structurally change. It converts into the corpus luteum (yellow in color) under the luteinizing hormone (LH).

Now, the corpus luteum will act as a gland and secretes the progesterone hormone. 

Generally, the corpus luteum has a 10-12 days life span. So, it produces progesterone for 10- 12 days.

Progesterone has a significant role in pregnancy. Progesterone comes to the uterus and makes the uterus wall thicker to achieve pregnancy.

Under the influence of progesterone, the endometrium layer becomes very reddish, thicker, more vascular, more glandular, softer, and warmer.

So, progesterone has a crucial role in preparing the uterus for conception. But what happens if fertilization does not occur….!


Day – 1 to 5 Menstrual Phase 

In ovary – 

If the ovum does not fertilize, the Corpus Luteum starts to degenerate. It develops into Corpus Albicans (white in color). 

In uterus – 

As time passes (after 10 days from ovulation), progesterone level dramatically becomes down. After that, the thick and vascularized endometrium layer (especially S.Functionalis) gets to the ischemic stage. 

Over time, endometrium cells become die, and necrosis occurs. These necrotic cells sloughed off, and bleeding gets started. 

This bleeding contains blood, prostaglandins, dead cells, and some fibrinolytic activity (to prevent a large blood clot).

This cycle repeats every month. 

Why is menstruation important for a female? 

Menstruation is a natural and important part of the female reproductive system. It is not a medical condition, and you should not try to suppress it.  

The menstrual period indicates that your reproductive system is working correctly. It tells that you are not pregnant. Moreover, it gives information that you have the ability to achieve pregnancy or get a baby if you do sexual intercourse at the time of ovulation. 


How much blood flow is normal during periods?

Every month, you lose blood 20 to 80 ml during the period. Sometimes, it may be a concern if it goes out of range. 

Your bleeding may be considered abnormal if you lost more than 80 ml, lasting more than 7 days. It is called heavy menstrual bleeding (or menorrhagia). Due to this, you may be more at risk of developing anemia.

But if you lose blood, less than 20 ml with a short duration period is considered a light period. It could be a sign of pregnancy or other diseases. 

You can measure your menstrual blood through a menstrual cup device. If you are having these problems during periods, you must consult a gynecologist. 


What does it mean when a female’s period is late?

Your menstrual period can be delayed or irregular during certain conditions –

a. Lactational amenorrhea – If you do breastfeeding, some hormones get imbalanced, which may cause a delay in your period.

b. Overweight or underweight – Too much weight or too little weight may also be a reason to disturb your menstrual cycle.

c. Intense exercise – Exercise is good for a healthy lifestyle. But too much exercise may reduce the level of estrogen that causes secondary amenorrhea

d. Chronic stress – If you have prolonged stress or any signs of depression, it induces cortisol hormone that delays your period.

e. Disruption of circadian rhythm – If you do work at night and sleep in the daytime, that may disrupt your menstrual period. Even it is mentioned in a study, the disruption of circadian rhythm may cause a delay in your period. 

f. Medications

According to a study, antipsychotic drugs (like olanzapine and quetiapine) increase prolactin hormone that induces amenorrhea. It may also disturb your period if you are on oral contraceptive pills or other medicines.

g. Medical conditions 

If you are dealing with any following medical conditions that could be a culprit in irregular menstrual periods.


How many days is a normal period last? Is it normal to not get your period every 28 days?

Normally, the average monthly cycle is 28 days. But it can vary in some females. Some females may have a shorter menstrual cycle, and some may have a longer one. So, the normal menstrual cycle range is 21 days to 35 days.

21 days———————28 days——————–35 days


You may need to worry. If your menstrual cycle frequently happens (less than 21 days) is called Polymenorrhea. And, if your menstrual cycle takes more than 35 days is called Oligomenorrhea.


How to calculate safe period in menstrual cycle? When is my most fertile day? 

If you have a regular menstrual cycle. You can easily calculate your fertile window. 

First of all, you should know your menstrual cycle days. After getting the proper days, you need to minus 14 days from the next menstrual cycle. 

Because ovulation is usually occurred just 14 days before the next cycle. 

What is a female period

For example – 

  • If you have 28 days menstrual cycle, then ovulation occurs on the 14th day. It will be a most fertile day. (28-14 = 14)
  • If you have 34 days menstrual cycle, then ovulation occurs on the 20th day. (34-14 = 20)
  • If you have 24 days menstrual cycle, then ovulation occurs on the 10th day. (24-14 = 10)


Day 14th, 20th, and 10th are the most fertile days in these examples. If you do sexual intercourse during these days, you may be more likely to conceive. And you may get pregnant easily. 

The rest of the days are less likely to get pregnant and consider a safe period for sex to avoid pregnancy. 



Now, you will have clarity about what is a female period cycle, how it happens, and why it happens in your body. 

Many females do not feel comfortable talking about menstruation with their doctor. If you have a problem regarding periods, you must consult a gynecologist. But you should never be shameful.

In this article, I have provided you depth information on the menstrual cycle. In my next post, I will be sharing what happens if the ovum gets fertilized with sperm (the process of fertilization). 

If you found this post (what is a female period) informative, please share it on social media. 


Sources –

1. Ross and Wilson. Anatomy and physiology in health and illness; 9th Edition, 2004. Churchill Livingstone. The reproductive systems, Chapter 19, Page 438.

2. Dhanalakshmi K et al. Physiology, Menstrual Cycle. Last updated Sep. 2020

3. Length and variation in the menstrual cycle–a cross-sectional study from a Danish county

4. Heavy Menstrual Bleeding. CDC

5. Periods. NHS (National Health Service)

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