The menstrual cycle consists of three phases - the menstrual, proliferative, and secretory phases. During the menstrual phase, the endometrium sheds if ovulation did not occur. In the proliferative phase, the endometrium thickens under rising estrogen levels. Ovulation occurs near the end of this phase. In the secretory phase, the corpus luteum secretes progesterone to prepare the endometrium for potential implantation. The cycle is regulated by changes in hormone levels and typically lasts around 28 days but can vary between individuals. Abnormalities include changes in cycle length, bleeding amount, or timing of menses.

1. The Menstrual Cycle/
Reproductive Cycle
By
Rani I. Gurudasani
M.pharm

2. The Menstrual Cycle
 The cycle consists of a series of changes taking place
concurrently in the ovaries and uterine lining, stimulated by
changes in blood concentrations of hormones.
 Menarche: First menstrual period
 Menopause: Termination of cycle due to normal aging of
ovaries
 The average length of the cycle is about 28 days.
 Phases of the Female Reproductive Cycle
 Three phases:
 1. Menstrual phase
 2. Preovulatory phase
 3.Postovulatory phase/ Secretory Phase

3. Phases of the Female Reproductive Cycle/
Menstrual Cycle

4. 1. Menstrual Phase:
Menses phase can last from 2 to 7 days, or longer
(average is 5 days).
When the ovum is not fertilised, the corpus luteum starts
to degenerate.
Progesterone and oestrogen levels therefore fall, due to
which endometrium lining shed in menstruation.
The menstrual flow consists of the secretions from
endometrial glands, endometrial cells, blood from the
degenerating capillaries and the unfertilised ovum.

5. 2. Proliferative Phase:
Most variable in length Day 6 – 13
Once menstrual flow stops, the endometrium begins to
proliferate again, marking the beginning of the
proliferative phase of the menstrual cycle.
At this stage an ovarian follicle, stimulated by FSH, is
growing towards maturity and is producing oestrogen.
Then due to oestrogen, thickness of endometrium
increases becoming very vascular and rich in mucus-
secreting glands.

6. 2. Proliferative Phase:
Increasing level of oestrogen triggers the
secretion of LH in mid-Cycle.
As the level of LH increases this triggers ovulation,
marking the end of the proliferative phase.

7. Hormone Level during each phase

8. 3. Postovulatory phase (Secretory phase):
Postovulatory phase most constant in duration at 14 days,
days 15 – 28.
After ovulation, LH from the anterior pituitary stimulates
development of the corpus luteum from the ruptured follicle.
Then corpus luteum produces progesterone, some
oestrogen and inhibin.
Under the influence of progesterone, the endometrium
becomes oedematous and the secretory glands produce
increased amounts of watery mucus.

9. 3. Postovulatory phase (Secretory phase):
This assists the passage of the spermatozoa through the
uterus to the uterine tubes where the ovum is usually
fertilised.
If fertilization does not occur, falling level of LH, degenerate
corpus luteum and converted into corpus albicans.
The resultant steady decline in circulating oestrogen,
progesterone and inhibin leads to degeneration of the uterine
lining and menstruation, with the initiation of a new cycle.
If the ovum is fertilised there is no breakdown of the
endometrium and no menstruation.

10. 3. Postovulatory phase (Secretory phase):
The fertilised ovum (zygote) travels through the
uterine tube to the uterus where it becomes
embedded in the wall and produces human
chorionic gonadotrophin (hCG), which is similar to
anterior pituitary luteinising hormone.

11. Fate of ovarian follicle during Menstrual cycle

12. Abnormalities of menstrual cycle
Changes in overall cycle length Polymenorrhea •Cycles with intervals < 21 days
Oligomenorrhea •Cycles with intervals of 35–90 days
Changes in length and/or
intensity of menses
Hypermenorrhea •Heavy menstruation with bleeding
volume > 150 mL (possibly visible
blood clots)
Menorrhagia •Bleeding volume > 80 mL and/or
length of menstruation > 7 days
Hypomenorrhea •Very low bleeding volume (< 25 ml)
Changes in timing of menses Metrorrhagia •Bleeding in between periods
Menometrorrhagia •Heavy and irregular bleeding
Spotting •Minimal bleeding seen in several
conditions