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Nursing Notes

The Menstrual Cycle

What the menstrual cycle is, its ovarian and uterine phases, the hormones that drive it, and the tests for ovulation.

Topic 1 of 3 · 6 min · 8 sections

1 Definition

Menstrual cycle
The visible manifestation of cyclic, physiological uterine bleeding.
  • It is due to shedding of the endometrium. shedding झड़ना
  • The outflow passes through the vagina to the outside.
  • It is followed by the interplay of invisible hormones: the HPO axis.

2 The HPO Axis

Gonad
Ovary or testis.
Trophin
To stimulate.
  1. Hypothalamus
  2. GnRHgonadotrophin releasing hormone
  3. Anterior pituitary gland
  4. GnH, that is FSH and LHgonadotrophin hormone
  5. Ovary
  6. secretes
  7. Estrogen and progesterone

Criteria of a menstrual cycle

  1. The HPO axis must be actively coordinated.
  2. The endometrium must be responsive to the ovarian hormones, estrogen and progesterone.
  3. The outflow tract (the vagina) must be patent, that is, clear.

3 Key Terms and Numbers

20 weeks of gestation7 millionAt birth2 millionAt puberty4 lakhAt menopause10,000070,00,000
Immature follicles fall from 7 million before birth to 10,000 at menopause. Drawn to scale.
Eumenorrhoea
Normal menstrual cycle.
Eutocia
Normal labour.
Menarche
The onset of menstruation.
Menopause
The permanent stoppage of menstruation.

The cycle starts with menarche and ends with menopause. Between them lies the female reproductive age, or child-bearing age, of about 15–45 years.

RememberThe numbers

Menses in a yearabout 13
Menses in a lifetimeabout 400
Bleeding phase1–5 days up to 7
Bleeding days2–7 days
Interval of the cycle21–35 days average 28
Amount of bleeding20–80 ml average 35

Content of the bleeding: mucus, dead endometrial cells, prostaglandins, microorganisms and plasmin enzyme. The colour is dark red.

4 Phases of the Menstrual Cycle

OvaryFollicular · 1–14Follicular · 1–14Luteal · 15–28Luteal · 15–28UterusBleeding · 1–5Proliferative · 6–14Secretory · 15–28Secretory · 15–28BleedingProliferativeOvulation · day 14161528day
The whole cycle on one ruler: the ovary and the uterus run side by side, not one after the other.

The same twenty-eight days are described twice: once by what the ovary does, once by what the uterus does. Read across each row.

Ovarian changes
Uterine changes
Follicular phase, day 1–14
Bleeding phase, day 1–5, then proliferative phase, day 6–14
Luteal phase, day 15–28
Secretory phase, day 15–28

5 Ovarian Changes

Follicular phase

  • Day 1 until ovulation; day 1–14.
  • The first half of the menstrual cycle.
  • The pre-ovulatory phase.

Ovulation happens 14 days before the next menstrual cycle. This is the rule that makes an irregular cycle calculable.

A 32-day cycle

32 − 14 = 18

Follicular phase: day 1–18. Luteal phase: day 19–32.

So the follicular phase is the variable phase variable बदलने वाली and the luteal phase is fixed.

  1. Immature follicles
  2. FSH
  3. Dominant follicle, the growing folliclesecretes estrogen
  5. Mature follicle, the Graafian folliclenamed for de Graaf, a Dutch physician
  6. LH
  7. Ovulationthe release of the ovum, a secondary oocyte
ImmaturefollicleDominantfollicleFSHGraafianfollicleOvulationLHCorpusluteumCorpusalbicans
The life of one follicle, left to right.

Luteal phase

  • Day 15–28.
  • The second half of the menstrual cycle.
  • The stable phase, fixed at 14 days.
  • The post-ovulatory phase.
  • Formation of the corpus luteum from the ruptured piece of the Graafian follicle.
  • The corpus luteum is yellow.
  • It secretes progesterone in large amount and estrogen in small amount.

Fate of the corpus luteum

If fertilisation occurs
If fertilisation does not occur
Becomes the corpus verum, the pregnant corpus, also called corpus gravitalis
Becomes the corpus menstrualis, or corpus haemorrhagicum (pink or red)
Continues to secrete progesterone for 3 months
Breakdown, luteolysis, leaves the corpus albicans, also called corpus candicans, which is white

6 Uterine Changes

Bleeding phase

  • Also known as periods, catamenia or menses.
  • Day 1–5, extending up to 7 days.
  • On days 26–28 the corpus luteum disappears.
  1. Decrease in progesterone and estrogen
  3. Vasoconstriction
  5. Hypoxia in endometrial cells
  7. Necrosis in endometrial cells
  9. Shedding of the endometrium
  11. Open blood vessels
  13. Bleeding and dead endometrial cells collect in the lower uterine segment
  14. the sensation transfers to the hypothalamus
  15. Posterior pituitary gland
  16. oxytocin
  17. Acts on the myometrium
  19. Uterine contraction starts
  21. The collected blood and cells are expelled through the vagina and become visible

Proliferative phase

  • Day 6–14, until ovulation.
  • The dividing phase.
  • Hyperplasia: an increase in the number of cells.
  1. Ovary: growing follicle, then Graafian follicle
  2. estrogen hormone
  3. Uterus
  5. Hyperplasia

Secretory phase

  • The fixed or stable phase.
  • Day 15–28.
  • The luteal phase: corpus luteum → progesterone and estrogen → hypertrophy of cells.
  • Also known as the preparatory phase.
  • If fertilisation occurs, it prepares for implantation.
  • If fertilisation does not occur, it prepares for shedding.
Bleeding1–2 mmProliferative3–4 mmSecretory8–10 mm010 mm
Endometrial thickness in each uterine phase, drawn to scale.

7 Hormonal Regulation

OvaryFollicular · 1–14Follicular · 1–14Luteal · 15–28Luteal · 15–28Peak estrogen · day 12Ovulation · day 14Peak progesterone · day 2111528day
When each hormone peaks, on the same 28 days.
Phase Hormone
Follicular phase FSH
Luteal phase LH
Ovulation LH
Bleeding phase decreased estrogen and progesterone
Proliferative phase estrogen
Secretory phase progesterone and estrogen
  • FSH has positive feedback with estrogen: as FSH rises, estrogen rises.
  • Estrogen has negative feedback to FSH and positive feedback to LH.
  • LH gives positive feedback to progesterone.
  • Progesterone gives negative feedback to LH, if fertilisation does not occur.

RememberHormone peaks

Peak level of estrogenday 12
LH surge36 hours before ovulation
Peak of the LH surge10–12 hours before ovulation
Peak level of progesteroneday 21

8 Diagnostic Tests for Ovulation

Spinnbarkeit test
Cervical mucus study. If the mucus stretches up to 10 cm, it indicates ovulation.
Fern test
Cervical mucus is visualised under the microscope. A fern-like pattern indicates ovulation.
Basal body temperature
Progesterone increases body temperature by 0.5–1 °F.

Basal body temperature chart

Ovulation
Anovulation
Biphasic pattern
Uniphasic pattern