What is Menstruation? | Phases of the Menstrual cycle | ScienceMonk

By-Ankita Satardekar,
M.Sc. Microbiology
 Contact- ankitasatardekar88@gmail.com

What is Menstruation?

In menstruation, the body of a woman discards the monthly buildup of the lining of the uterus. Menstrual blood and tissues flow from the uterus through the small opening in the cervix and pass out through the vagina. This uterus lining builds up to prepare for pregnancy. If a woman is not pregnant, estrogen and progesterone hormone levels fall which is a signal for the body to begin menstruation.



What is the Menstrual Cycle?

The menstrual cycle is a hormonal cycle to prepare a female’s body for pregnancy. It starts from the first day of your period up to the first day of your next period. The hormone levels (estrogen and progesterone) usually change throughout the menstrual cycle and can cause specific menstrual symptoms such as cramping, mood swings, fatigue, and bloating, etc. The menstrual cycle is composed of two cycles – one that occurs in the ovaries and one in the uterus.

Menarche and Menopause-(Menstruation)

Menarche is the first menstrual period, considered as a start. It usually occurs between the age of 11 and 16.
Menopause is the time when periods stop permanently which is also called as “climacteric.”
The timing of these phases is critical for a woman’s health trajectory over her lifespan, as they indicate ovarian function and aging. Both early and late timing of either one of these phases is associated with the risk of adverse health and psychosocial outcomes.

Phases of the Menstrual cycle

  • Menstruation (The period): 1st phase of Menstruation

In this phase, the blood and endometrium forming the lining of the uterus shed through the cervix and vagina while levels of estrogen and progesterone are low. It may last up to 8 days but on average lasts about 5 or 6 days.Menstruation

  • The Follicular Phase: 2nd phase of Menstruation

During the period, the pituitary gland produces a hormone called follicle stimulating hormone (FSH). FSH signals the ovaries to prepare an egg for ovulation. Throughout the menstrual cycle, there are multiple follicles that look like fluid-filled sacs containing eggs in each ovary.

As the period is about to end, a follicle in one of the ovaries is the largest of all the follicles (around 1cm). This follicle becomes the dominant follicle and is the one which is prepared to be released during the ovulation phase.

As the dominant follicle grows, it produces estrogen which peaks just before ovulation process. It may last up to 10-22 days.

  • The Proliferative Phase:- 3rd Phase of Menstruation

After the period, the uterine lining starts building up again. While the ovaries are developing the egg-containing follicles, the uterus is responding to the level of estrogen produced by the follicles, rebuilding the lining which was shed during the last period. Endometrium or the lining of the uterus becomes thicker than before.

  • Ovulation: 4th phase of Menstruation

The dominant follicle in the ovary keeps on producing more and more estrogen as it grows in size. The dominant follicle reaches about 2 cm right before ovulation.

When estrogen levels are sufficiently high, a signal is sent to the brain causing a dramatic increase in luteinizing hormone; this is what causes ovulation which is the release of an egg from the ovary. It may last up to 13-15 days before the next period starts.


  • The Luteal Phase: 5th phase of Menstruation

The time between ovulation and start of menstruation, when the body prepares for a possible pregnancy. Progesterone is produced, peaks, and drops further. Once ovulation occurs, the follicle that contained the egg transforms into a corpus luteum and starts to produce progesterone and estrogen.

Progesterone levels peak about halfway through the luteal phase. The hormonal changes are associated with common premenstrual symptoms such as mood changes, headaches, acne, bloating, and breast tenderness. If an egg is fertilized, progesterone from the corpus luteum supports the pregnancy although If not then fertilization occurs and corpus luteum starts to break down between 9 and 11 days after ovulation. It leads to a drop in estrogen and progesterone levels, which causes menstruation.

  • The Secretory Phase: 6th Phase of Menstruation

During the secretory phase, the endometrium prepares to either support a pregnancy or to break down for menstruation. As the progesterone level rises, it can cause the endometrium to stop thickening and to start preparing for the potential attachment of a fertilized egg.

There are two prostaglandins “PGF2α” and “PGE2”, causing the uterine muscle to contract (cramp). The cramping helps trigger the period. If pregnancy occurs, the production of prostaglandin is inhibited so that contractions won’t impact pregnancy.

But if pregnancy does not occur, the corpus luteum stops production of estrogen and progesterone. The fall in hormones, along with the prostaglandins, cause the blood vessels to constrict and tissue of the endometrium to break down.

You may also like to read Cellular Respiration

What is Premenstrual Syndrome (PMS)?

PMS is both physical and emotional symptoms that many women get after ovulation and before the start of a period. It is due to fall in the level of estrogen and progesterone. PMS symptoms are different for every woman.

There can be physical symptoms such as swollen or tender breasts, bloating, cramping, headache and emotional symptoms such as mood swings, sleeping problems, appetite change, anxiety, and hostile behavior, etc.

You may also like to read- Breast Cancer Awareness- Everything You need to Know

Improper Menstrual Hygiene Management (MHM)

Menstrual hygiene is an important issue affecting healthy adolescent girls and pre-menopausal adult women. MHM depends on the social and economic status, personal preferences, culture, and beliefs of an individual as well as access to water and sanitation resources.

Improper MHM practices increase a woman’s exposure to urogenital infections, such as bacterial vaginosis and urinary tract infection. Bacterial vaginosis is a poly-microbial syndrome characterized by the imbalance in bacterial flora in the vagina.

The normal vaginal flora is dominated by Lactobacilli producing hydrogen peroxide which acts as an anti-bacterial agent. In Bacterial vaginosis, there is a fall in the population of Lactobacilli with a simultaneous increase in the harmful bacterial community.

Urinary tract infection (UTI) is the most common type of infectious disease among the girls and women of menstruating age.

What is Toxic Shock Syndrome?

Toxic shock syndrome (TSS) is a rare although life-threatening condition caused by bacteria that release harmful toxins. It’s generally associated with tampon use in young women. Toxic shock syndrome is caused by bacteria such as Staphylococcus aureus and Streptococcus pyogenes, although most cases are related to Staphylococcus aureus.

When Streptococcus pyogenes causes TSS, it’s usually because the bacteria got into areas of injured skin, such as cuts, scrapes, surgical wounds, and even chickenpox blisters.

Specific symptoms are high fever (temperature at least 102°F), a rapid drop in blood pressure, diarrhea, headache, rashes on the body (usually the palms of the hands and the soles of the feet) and muscle ache.

Washing hands well before and after inserting a tampon, alternating tampons with sanitary napkins or using right quality tampons with the lowest absorbency, changing the tampons often on low-flow days and storing tampons away from heat and moisture to avoid the growth of bacteria can prevent TSS.

Leave a comment