Understanding of The Menstrual Cycle and Its Phases

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There are various myths around menstruation that give rise to social, cultural, and religious norms, and that prevent women from participating in various activities during menstruation. In most cultures, women are not allowed to enter temples and perform religious practices. In some cultures, sex during the menstrual cycle is considered taboo.

These beliefs and taboos lack a scientific explanation and have created misunderstandings about menstruation. This is because most women themselves lack the understanding of their very own menstrual cycle.

This article aims to help women understand what a menstrual cycle is and what are the different phases involved.

What is a Normal Menstrual Cycle?

The menstrual cycle, or menstruation, or commonly known as ‘periods’, is the shedding of the uterine lining periodically. Menstrual blood flows from the uterus (womb) through the cervix (the lower portion of the uterus) and out of the body through the vagina (a soft, muscular canal that connects the uterus to the outside world).

In other words, a period is a time when a woman’s body releases tissue it no longer needs.

This tissue comes from the uterus, which is where a baby (fetus) can develop in a woman. Every month, the lining of the uterus gets thicker to prepare for a fertilized egg (primary female gamete), to support pregnancy. If the egg doesn’t get fertilized, that lining is released from the body in the form of blood, through the vagina. This monthly process is called menstruation or menses.

A normal menstrual cycle is 28 days long but it can range anywhere between 21 to 35 days. The menstrual cycle is controlled by various hormones (chemical messengers that help carry out body functions) involved in the HPO axis (hypothalamic-pituitary-ovarian axis) which is a tightly regulated system controlling female reproduction.

Phases of The Menstrual Cycle

The menstrual cycle refers to the set of natural changes in the uterus and the ovaries (primary female reproductive organ) that make reproduction possible. The menstrual cycle is further divided into:

1. Ovarian cycle is responsible for the production and release of eggs. The ovarian cycle consists of 3 phases which are follicular (preovulatory) phase, ovulation, and luteal (post-ovulatory phase).

2. Uterine cycle prepares the lining of the uterus to receive a fertilized egg, leading to pregnancy. The uterine cycle consists of 3 phases which are divided into menstruation, proliferative (postmenstrual), and secretory (premenstrual) phase.

The phases in the menstrual cycle are regulated by the female sex hormones, namely estrogen, and progesterone.

  • Estrogen is responsible for the development of the female reproductive system and it imparts female sex characteristics such as breasts and pubic hair. It maintains the thickness of the vaginal wall and promotes lubrication.
  • Progesterone is responsible for regulating the menstrual cycle and supporting pregnancy in women.

What are FSH and LH and Their Functions?

Follicle-stimulating hormone (FH) and Luteinizing hormone (LH) are glycoproteins that are secreted by your pituitary gland in response to the hormone GnRH (gonadotropin-releasing hormone) released by the hypothalamus in your brain.

  • In females, Luteinizing hormone (LH) stimulates the production of estrogen and progesterone from the ovary. A sudden increase of LH (LH surge) which occurs in the middle of the menstrual cycle, causes ovulation.
  • Continued secretion of LH stimulates the corpus luteum to produce progesterone. The corpus luteum is a temporary gland within the ovary that regulates the menstrual cycle and early pregnancy. It forms the ovarian follicle wall during ovulation.
  • The development of an ovarian follicle is largely dependent on FSH.

An overview of the Ovarian and Uterine Cycles

Let’s divide the menstrual cycle into 2 parts:

First Part of the Cycle: Menstruation (occurs in Uterus), Follicular Phase (occurs in Ovaries), and Proliferative Phase (occurs in Uterus).

Interlude (In Between): Ovulation (occurs in Ovary)

Second Part of the Cycle: Luteal Phase (occurs in Ovary) and Secretory Phase (occurs in Uterus)

The menstrual cycle is set as follows:

Menstruation—-Follicular phase—-Proliferative Phase—-Ovulation—-Luteal Phase—-Secretory Phase— Menstruation (cycle repeats)

Menstruation is a cyclic process and it repeats itself every 28 to 35 days.

1. Uterus: Menstrual Phase or Menstruation

This phase involves the shedding of the uterine lining, in the form of blood through the vagina. It starts on the first day of a woman’s period and can last for up to 5 or 6 days. It is the first and the most evident phase of the uterine cycle.

During this phase, the production of hormones is less and a woman is likely to experience symptoms such as abdominal pain, abdominal cramps, fatigue, irritability, nausea, and weakness. For some women, the bleeding is light, whereas for some, it can be heavy.

2. Ovaries: Follicular (Preovulatory) Phase

The follicular phase starts from day 6 or day 7 and lasts up to day 14. It is the first part of the ovarian cycle during which ovarian follicles (sacs of fluid present on the outside layer of the ovaries which contain immature eggs) mature to release an egg. Remember that each of the ovaries of a woman has a limited number of eggs.

During this phase, estrogen levels rise and cause thickening of the uterine lining. The rise in the levels of the hormone called FSH (Follicle-stimulating hormone) causes follicles to grow in size and develop into mature eggs.

Additionally, LH further stimulates the development of the ovarian follicle. The follicle that reaches maturity, also called the tertiary follicle, contains the ovum (egg cell).

3. Uterus: Proliferative Phase

The term “proliferative” means that cells are multiplying and spreading. After the menstruation phase, estrogen levels rise, causing the uterine lining to build and thicken up again.

4. Interlude: Ovulation

Ovulation is the second phase of the ovarian cycle. Ovulation typically lasts one day and occurs between day 14 to 28 of a woman’s menstrual cycle.

It is characterized by the release of an egg from one of a woman’s ovaries. After the egg is released, it travels down the fallopian tube (female reproductive organs that connect the ovaries and the uterus), where fertilization by a sperm (primary male gamete) may occur.

Ovulation from either of the two ovaries – left or right, happens randomly and there is no right or wrong. Once the egg is released from the ovary, the egg is pushed into the fallopian tube. If there is no sperm to fertilize the egg, the unfertilized egg, after about a day, will degenerate in the fallopian tube. On the other hand, a fertilized egg will reach the uterus in three to five days.

5 Ovary: Luteal Phase

It occurs from day 15 to 28 and causes mature eggs to travel through tubes to the uterus. Progesterone hormone prepares the uterus for pregnancy.

If an egg is fertilized by a sperm, then the embryo (early stage of human development) attaches to the uterus and pregnancy occurs. If pregnancy doesn’t happen, then hormone levels (FSH and LH) fall, leading to menstruation.

6. Uterus: The Secretory Phase 

After ovulation, both hormones (estrogen and progesterone) are secreted in large quantities by the corpus luteum. The secretory phase of the uterine cycle coincides with the luteal phase of the ovarian cycle.

Estrogen causes increased thickening of the wall of the uterus and progesterone causes an increase in swelling and secretion of thick viscous fluid which makes the uterine glands elongated. The corpus luteum is filled with increased nutrients and is ready for implantation of the fertilized ovum (egg).

If fertilization does not occur, the corpus luteum degenerates, and the level of estrogen and progesterone falls leading to menstruation.

More Points to Remember

Menstruation generally starts at the age of 12 (menarche, known as the first menstruation) and usually stops between the age of 45 and 55 years (known as menopause).

Certain symptoms which indicate the need to consult a doctor include:

  • Menarche (the first menstruation cycle) not achieved up to 16 years
  • Menstruation/periods stops suddenly
  • Menstruation/periods last for more days with heavy bleeding or passage of clots (clumps of blood)
  • Irregular periods/pain during periods
  • Postmenopausal bleeding

It is very important to understand menstruation from a hygiene point of view and not associate it with impurity or other taboos. Women should keep the genital area clean and change sanitary napkins or tampons every 3-4 hours to prevent UTI (Urinary Tract Infection) or any bacterial or fungal infections. Sanitary napkins and tampons are menstrual hygiene products used by women during the first 6 days of menstruation.

Consulting a gynaecologist is advisable to clear any doubts regarding menstruation. Do not to fall prey to myths and taboos about menstruation.

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