Menstrual cycle

1. MENSTRUAL CYCLE
The menstrual cycle is a concurrent series of changes in endometrium of the uterus to
prepare it for the arrival of fertilised ovum that will develop there until birth. If fertilization
doesn’t occur, ovarian hormones wane which causes endometrium to slough off. This is
generally term as female reproductive cycle.
OR
The menstrual cycle is a series of natural changes in hormone production and structures of
the uterus and ovaries of female reproductive system that makes pregnancy possible.
PHASES IN THE FEMALE REPRODUCTIVE CYCLE:
The duration of female reproductive cycle typically ranges from 24-35 days throughout the
child bearing period between menarche & menopause. The average length of the cycle is 28
days.
Menstrual cycle: usually lasts for roughly about 4-5 days.
Proliferative phase: approximately 10 days.
Ovulatory phase: at 14 day.
Secretory/ luteal phase: after 14 days.

2. Phases Events in ovaries Events in uterus
MENSTRUAL
PHASE
Under the influence of FHS
several primordial follicles
develop into primary follicles and
then into secondary follicles.
Menstrual flow from uterus consist
of 50-150ml of blood, tissue and
epithelium cells shed from the
endometrium.
Declining levels of progesterone &
oestrogen stimulate release of
prostaglandin
Causes the arteriolar to constrict.
Cell become oxygen deprived and
start to die
This leads to shedding off
functional layer of endometrium.
(At this time endometrium is very
thin, about 2mm-5mm, because
only stratum basils remains.)
Menstrual flow passes from
uterine cavity through cervix and
vagina.

3. Proliferative phase At this stage an ovarian follicles,
stimulates by FHS is growing
toward maturity and is producing
oestrogen which stimulates
proliferation of functional layer of
endometrium in preparation for
receiving a fertilized ovum.
Endometrium thickens,
Becoming vascular and rich in
mucus secreting gland.
Raising the level of estrogen
which is responsible for triggering
a surge of LH approximately at
mid of cycle.
This sudden increase in LH level
leds to ovulation.
OVULATORY
PHASE
• During ovulation the
secondary oocyte remains
surrounded by its ZONA
PELLUCIDA.
• LH causes rapture of
mature follicle & expulsion
of secondary oocyte about
9 hrs after peak of LH
surge.
The ovulated oocyte swept
into uterine tube
• From time to time an
oocyte is lost into pelvic
cavity where it later
disintegrates. The small
amount of blood that can
cause pain known as
MITTELSCHMERZ at
time of ovulation.
Only ovarian changes are there
in this phase
SECRETORY/
LUTEAL PHASE
AFTER OVULATION THE
MATURE FOLLICLE
COLLAPSE &BASEMENT
MEMBRANE BETWEEN THE
GRANULOSA CELLS AND
SUPERFICIAL ENDOMETRIUM
THICKEN AND BECOME
VASCULAR(12MM-18MM).
BECAUSE OF SECRETORY
ACTIVITY OF ENDOMETRIAL
GLANDS, WHICH BEGIN TO

4. THECA INTERNA BREAKS
DOWN.
BLOOD CLOT FORMATION
(CORPUS HEMORRHAGIUM)
THECA CELLS GETS MIXED
WITH GRANULOSA CELLS
AND TRANSFORMED INTO
CORPUS LUTEUM.
THIS SECRETES
PROGESTERONE,
ESTROGEN,RELAXIN AND
INHIBIN
THIS CORPUS LUTEUM
ABSORB BLOOD CLOT,
THEREFORE CALLED LUTEAL
PHASE. (CORPUS LUTEUM HAS
LIFE OF 2WEEKS ONLY)
CORPUS ALBICANS
SECRETE GLYCOGEN
THEREFORE, IT IS CALLED
SECRETORY PHASE.
THESE CHANGES ARE PEAK
FOE ONE WEEK AFTER
OVULATION.
AT THIS TIME FERTILISED
OVUM MAY ARRIVE IN THE
UTERUS.
IF FERTILIZATION DOESN’T
OCCUR
Decline level of progesterone
estrogen due to degeneration of
corpus luteum.
ULTIMATELY WITHDRAWAL
OF PROGESTERONE CAUSES
MENSTRUATION.

5. DIAGRAM SHOWING CHANGES IN THICKNESS OF
ENDOMETRIUM, OVARIES, BODY TEMPERATURE
AND HORMONES