Introduction and Phases of Mensuration

Subject: Midwifery I (Theory)

Overview

Menstruation is the discharge of blood and mucus from the inner lining of the non-pregnant uterus on a regular basis. Except during pregnancy, it is controlled by hormones and recurs at regular intervals of 28 days. The menstrual cycle is the cyclic process of menstruation that provides the preparation for pregnancy. If pregnancy does not occur, the endometrium degenerates and the cycle recommences. It happens every 28-30 days on average, although it can happen every 21-42 days. This cycle involves three major organs. To complete a menstrual cycle, each organ has its own cycle. The three main organs involved in this cycle are the pituitary gland, the ovary, and the uterus. The menstrual cycle is a series of events that occur on a regular basis. The proliferative phase lasts 10 days, the secretory phase 14 days, and the menstruation phase 4 days. At the conclusion of menstruation, the proliferative phase begins. The anterior lobe of the pituitary gland secretes FSH during this phase. The secretary phase begins after ovulation and lasts around two weeks or fourteen days. The pituitary glands begin secreting the second gonadotrophin, the luteinizing hormone, immediately after ovulation. The menstrual cycle lasts approximately 4-6 days. The usual amount of blood flow throughout each cycle is 60-90 ml.

Menstruation is the discharge of blood and mucus from the inner lining of the non-pregnant uterus on a regular basis. The discharge occurs through the vagina. Except during pregnancy, it is controlled by hormones and recurs at regular intervals of 28 days. Menstruation lasts from menarche through menopause.

Mechanism of Menstruation or Menstrual Cycle

The menstrual cycle is the cyclic process of menstruation that provides the preparation for pregnancy. If pregnancy does not occur, the endometrium degenerates and the cycle recommences. It happens every 28-30 days on average, although it can happen every 21-42 days.

This cycle involves three major organs. To complete a menstrual cycle, each organ has its own cycle.

  1. Pituitary Gland
  2. Ovary
  3. Uterus

The Pituitary Gland

The hypothalamus is responsible for the release of luteinizing hormones. The anterior pituitary gland is stimulated to secrete:

  1. Follicle-stimulating hormones (FSH) stimulate ovarian follicle maturation and estrogen release, resulting in ovulation. It grows until ovulation, then progressively decreases.
  2. Luteinizing hormone (LH) increases corpus luteum formation and progesterone release. The hormone made the endometrium thick, vascular, and spongy.

Changes in hormone concentrations in the blood induce FHS and LH secretion. A negative feedback mechanism regulates hormones released during the cycle.

The Ovarian Cycle

One or more ovules will be liberated at the same moment as a result of hormonal stimulation under the impact of FHS. The ovary produces estrogen and progesterone, which thickens, vascularizes, and specifies the endometrium, which is lost during menstruation. Each ovary ovulates every two months. Under the action of LH, the surviving membrane granulosa cells multiply.

 

The Uterine Cycle or Menstrual Cycle

The menstrual cycle is the time between the first and second menstruation. The menstrual cycle is a set of events that occur at regular intervals over a period of around 28 days and are divided into three parts.

  • The proliferative phase: 10 days
  • The secretory phase: 14 days
  • The menstrual phase: 4 days

The Proliferative Phase

This stage begins at the end of the menstrual cycle. The anterior lobe of the pituitary gland secretes FSH during this phase. This hormone helps the primordial follicle develop and mature into the Graafian follicle. Normally, only one ovum develops and matures during this period, but two or more may do so.

During this time, the ovary secretes estrogen. This hormone enters the bloodstream directly and has an effect on the endometrium, driving columnar cells to duplicate the endometrium more quickly, generating a thicker lining and increasing the number of glands and blood capillaries, making the lining more vascular and spongy. This phase can last up to ten days beginning on the fourth day of the previous menstruation. By the end of this phase, the endometrium is 2-3 mm thick.

When an ovum matures, the follicle ruptures and the ovum enters the peritoneal cavity due to the high level of luteinizing hormone. Ovulation is the release of the ovum from the follicle. When ovulation occurs, this phase ends and the secretory phase begins.

The Secretory Phase

The phase begins after ovulation and lasts approximately two weeks or fourteen days. The pituitary glands begin secreting the second gonadotrophin, the luteinizing hormone, immediately after ovulation.

This hormone causes the remaining ovarian follicle cells to form the corpus luteum or yellow body. Under the influence of the luteinizing hormone, the corpus luteum begins to secrete progesterone, the second ovarian hormone.

Progesterone is taken straight into the bloodstream and acts on the endometrium, supplementing the activity of estrogen. It causes the lining to thicken, even more, the endometrial glands to get larger and more convoluted, stores a huge amount of glycogen, increases blood capillaries, and initiates the secretory activity. The gland produces more secretion, which is then discharged into the uterine cavity.

The endometrium is now thick, soft, moist, vascular, and densely packed with blood vessels, and it is ready to receive a fertilized egg. The thickness of the endometrium is 4-6 mm.

If the ovum is fertilized, there is no endometrial breakdown and no menstrual flow. As a result, the endometrium is now known as decidua. The fertilized ovum embeds itself into the endometrium and produces a hormone called human chorionic gonadotrophin hormone, which maintains the corpus luteum's integrity and allows it to continue secreting progesterone. Menstrual bleeding develops if the ovum is not fertilized.

The Menstrual Phase

If the ovum is not fertilized, the high quantity of progesterone in the blood inhibits pituitary gland activity and significantly reduces LH production. Withdrawal of this hormone causes shrinkage and degeneration of the corpus luteum, resulting in decreased progesterone production. Menstrual bleeding is caused by the deterioration and breakdown of the uterine inner lining. It has blood, inner lining cells, and an unfertilized ovum. This lasts approximately 4-6 days. The usual amount of blood flow throughout each cycle is 60-90 ml.

When the progesterone level in the blood falls below a particular threshold, the pituitary gland resumes secretion of the follicle-stimulating hormone. The cycle is restarted when another ovarian follicle is activated.

References

  • Web MD. 2005. 2017 http://www.webmd.com/baby/guide/understanding-conception#1
  • Medline Plus. 05 January 2017 https://medlineplus.gov/menstruation.html
  • MedicineNet. 1996. 2017 http://www.medicinenet.com/trying_to_conceive/article.htm
  • Tuitui R. 2002, A textbook of Midwifery A (Antenatal), 3rd edition, Vidyarthi Pustak Bhandari (Publisher and Distributor), Bhotahity, Kathmandu
  • Tuitui R., Suwal, S.N. 2001, Human anatomy and physiology, first edition, Makalu Books and stationers, Putalisadak, Kathmandu
  • WHO, UNFPA, UNICEF, 2003. Pregnancy, childbirth, Postpartum and Newborn care (PCPNC): A guide for essential practice, “IMPAC” World bank.
Things to remember
  • Menstruation is the discharge of blood and mucus from the inner lining of the non-pregnant uterus on a regular basis.
  • Except during pregnancy, it is controlled by hormones and recurs at regular intervals of 28 days.
  • The menstrual cycle is the cyclic process of menstruation that provides the preparation for pregnancy. If pregnancy does not occur, the endometrium degenerates and the cycle recommences.
  • It happens every 28-30 days on average, although it can happen every 21-42 days.
  • This cycle involves three major organs. To complete a menstrual cycle, each organ has its own cycle. The three main organs involved in this cycle are the pituitary gland, the ovary, and the uterus.
  • The menstrual cycle is a set of events that occur at regular intervals over a period of roughly 28 days and are divided into three separate phases: the proliferative phase, the secretory phase, and the menstrual phase.
  • At the conclusion of menstruation, the proliferative phase begins. The anterior lobe of the pituitary gland secretes FSH during this phase.
  • The secretary phase begins after ovulation and lasts around two weeks or fourteen days. The pituitary glands begin secreting the second gonadotrophin, the luteinizing hormone, immediately after ovulation.
  • The menstrual cycle lasts approximately 4-6 days. The average volume of blood flow throughout each cycle is 60-90 ml.
Videos for Introduction and Phases of Mensuration
Ovulation & the menstrual cycle
The Menstrual Cycle
Questions and Answers

Mechanism of menstruation or menstrual cycle

When a pregnancy does not materialize, the endometrium degenerates and the cycle restarts. This cyclical process of menstruation is known as the menstrual cycle. It happens typically every 28 to 30 days, but occasionally it happens every 21 to 42 days.

This cycle involves three major organs. Every organ has a unique cycle that it follows to complete a menstrual cycle.

  • Pituitary gland
  • The ovary gland
  • The uterus

Pituitary gland:

Luteinizing hormone-releasing hormone is secreted by the hypothalamus. The anterior pituitary gland is stimulated by this to secrete:

  • FSH, or follicle stimulating hormones, encourage the development of ovarian follicles and the release of estrogen, which results in ovulation. Up until ovulation, it grows before gradually declining.
  • LH, or luteinizing hormone, which promotes progesterone secretion and corpus luteum development. The endometrium became thick, vascular, and spongy as a result of the hormone.

Changes in the blood concentration of hotmones stimulate the secretion of FHS and LH. The cycle's hormone secretion is controlled by a negative feedback mechanism.

The ovarian cycle:

One or more ovules may be released at once from hormonal stimulation under the influence of FHS. The endometrium, which is shed during menstruation, is created thick, vascular, and spongy by the estrogen and progesterone the ovary generate. Every ovary ovulates twice per month. LH causes the remaining membrane-containing granulose cells to multiply.

The uterine cycle or menstrual cycle:

The interval between the first and succeeding periods is known as the menstrual cycle. The menstrual cycle is made up of three distinct phases and a series of events that occur at regular intervals over a period of about 28 days.

  • The proliferative phase - 10 days
  • The secretory phase - 14 days
  • The menstrual phase - 4 days
     
  • The proliferative phase: When menstruation is finished, this phase starts. The anterior lobe of the pituitary gland secretes FSH during this stage. This hormone helps the primordial follicle grow and mature into the graafian follicle. Typically, only one ovum develops and matures during this time, but occasionally two or more may do so. Ovarian glands secrete the hormone estrogen during this time. This hormone enters the bloodstream directly and affects the endometrium by causing the columnar cells to multiply the endometrium more quickly, forming a thicker lining, and increasing the number of glands and blood capillaries, which results in a more vascular and spongy endometrium. From the fourth day after the previous menstruation, this phase might extend up to 10 days. The endometrium is 2-3 mm thick by the time this period is over. A mature ovum is released into the peritoneal cavity when a follicle ruptures due to a high level of luteinizing hormone. Ovulation is the term used to describe the release of the ovum from the follicle. When ovulation occurs, this phase ends, and the secretary phase starts.

  • The secretary phase:After ovulation, the phase lasts for around two weeks, or 14 days. The pituitary glands begin secreting the second gonadotrophin, or luteinizing hormone, right after ovulation. The corpus luteum, or yellow body, is created by the hormone's stimulation of the ovarian follicles' surviving cells. Luteinizing hormone causes the corpus luteum to begin secreting progesterone, the second ovarian hormone. Directly absorbed into the bloodstream, progesterone affects the endometrium and enhances the effects of estrogen. It causes the endometrial lining to thicken even more, the endometrial glands to enlarge and become more tortuous, to store a lot of glycogen, which expands blood vessels, and to start secreting. The gland releases more of their secretion into the uterine cavity. The endometrium is ready to receive a fertilized ovum at this point because it is thick, soft, moist, vascular, and rich in blood capillaries. The thickness of the endometrium is 4-6 mm. Fertilization of the ovum prevents endometrial breakdown and menstrual flow. Endometrium is now known as decidua as a result. The human chorionic gonadotrophin hormone, which is produced by the fertilized ovum when it embeds itself in the endometrium, keeps the corpus luteum intact and enables it to continue secreting progesterone. In the absence of fertilization, menstrual bleeding starts.

The menstrual phase:

If the ovum does not become fertilized, the pituitary gland's function is inhibited by the high levels of progesterone in the blood, which significantly lowers the amount of LH produced. The corpus luteum shrinks and degenerates as a result of the hormone's withdrawal, which lowers progesterone levels. Menstrual bleeding is brought on by the uterine lining degenerating and disintegrating. It includes unfertilized ovum, inner lining cells, and blood. This persists for four to six days. 60 to 90 ml of blood should normally flow during each cycle.

The pituitary gland once more begins to secrete follicle stimulating hormone when the blood progesterone level reaches a certain level. After stimulating a new ovarian follicle, the cycle repeats.

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