The document summarizes the physiology of the human menstrual cycle. It describes the four phases - menstrual, follicular, ovulatory, and luteal. Key events include menarche beginning the cycle around age 14 and menopause ending it around age 50. The ovarian cycle involves follicle maturation and ovulation in response to hormones. The uterine cycle involves changes to the endometrium also in response to hormones that prepare it for potential pregnancy.

1. Physiology of menstrual
cycle
Unit - II

2. Introduction
 Typically a women of child bearing age or
reproductive age (15 -45 years) should menstruate
every 28 days or so unless she is pregnant or moving
into menopause .
 Amenstrual cycle consist of natural changes that
occur in a women body every month in prepration for
pregnancy .
 Menstruation starts at puberty and ends at
menopause
 Eumenorrhea is term for normal
menstruation

3. Definition
 Menstruation means cyclic uterine bleeding caused
by shedding of progestational endometrium. It
occurs between menarche and menopause .
 Menstruation is also called menstrual bleeding,
menses or periods.
OR
 The cyclic events that takes place in a rhythmic
manner during the reproductive period of a
woman’s life is called menstrual cycle.

4. Characterstics
1. Menarche :- First occurance of
menstruation . Starts at 12 to 16 years .
Average 14 years .
2. Menopause :- Permanent cessation of
menstrual cycle . Usually at 45- 50 years.
3. Duration :-2 to 7 days ( < 2 days in
hypomenorrhea and >7 days in menorrhagia.
4. Amount :- 30 to 80 ml. >80 ml is menorrhagia &
<30 ml is hypo menorrhea.

5. Contd…
• 5 . Coagulation :-
 Some authors state that the mixture of mucus with
menstrual blood prevents the clotting of the
menstrual blood .
 Others state that the acidity of vaginal secretion is
responsible for non coagulibility .
 Some states that it does not clot due to
present in endometrial debris .

6. Hypothalmic - Pituitary
OvarianAxis
Hypothalmus
Gland
Secrete Gonadotrophin Releasing
Harmones
FS
H
L
H

7. Phases in menstrual cycle
 There are 2 main components of the menstrual
cycle :-
1. Ovarian Cycle
2. Uterine Cycle
 Ovarian Cycle :- Changes happen in
ovaries in response to pituitary harmones .
 Uterine Cycle :- Changes that takes place
in the uterus .
 But it is important to remember that both cycles
work simultaneously to produce menstrual cycle .
 Changes in the cervical mucus also takes place
during menstrual cycle .

8. Ovarian cycle
 The ovarian cycle refers to periodic changes
that occur in the ovary every month during the
female reproductive life .
 Cyclical changes in the ovaries occur in response to
2 anterior pituitary harmones .
1. Follicle stimulating harmone (FSH)
2. Luteinizing harmone (LH)

9. Uterine cycle
 The uterine cycle refers to changes that are found in
the lining of the uterus
 The changes come about in response to the ovarian
harmones :-
 Estrogen
 Progesterone

11. Phases of menstrual cycle
 There are 4 phases of menstrual cycle .
1. Menstrual phase
2. Follicular OR preovulatory OR
proliferative phase
3. Ovulation OR Ovulatory phase
4. Luteal OR Post ovulatory OR secretary Phase

12. Menstrual phase
 It is called Bleeding phase .
 Average duration of this phase is 3-5 days .
 Day 1 of the menstrual cycle is marked by onset
of menstruation.
 During the menstrual phase the uterine lining is shed
 The menstrual flow consist of the secretions from the
endometrial gland , endometrial cells , blood from
the degenerating capillaries and unfertilized ovum.
 The menstrual phase ends when menstrual period stops
on day 5.

13. Follicular &Pre ovulatory
and Proliferative phase
 This phase of the cycle extends from the day 5th of
the menstrual phase till the time of ovulation .
 This phase generally lasts for 8-9 days .
 During this phase some 10 - 15 primordial follicles
start maturing .
 But only one follicle of one of the ovaries reaches
maturity.The mature follicle is called which
secretes estrogen .
 Estrogen has a negative feedback on the FSH .
 This is to stop the other follicles from maturing .

14. OVULATORY PHASE
 Estrogen peak stimulates the secretion of LH.
 LH peak leads to :-
The follicle to burst open releasing the mature ovum .
This is called as ovulation .
 Ovulation occurs on 14 th day of each 28 day cycle

15. POSTOVULATORY or
SECRETARY PHASE
 This phase starts from day 15 and last till
the end of cycle that is from day 15 to 28.
 After ovulation LH levels remains elevated
and cause the remnants of the follicle to
develop into a yellow body called corpus
luteum .
 Corpus luteum secretes mainly Progesterone and
some oestrogen
• These 2 harmones function to maintain the lining of
the uterus that is endometrium and prepare it for
pregnancy

17. Luteal phase
 When there is no fertilization for about 7-8 days
then degeneration of corpus luteum starts .
 Due to corpus luteum degeneration level of
estrogen and progesterone also falls down .
 Corpus luteum then changes to corpus albicans
and then it is reabsorbed .
 Cells or lining of endometrium develops
a condition of ischemia . So they starts to fall
down or there shedding starts .
 And women is once again at the day 1 of
menstrual cycle .

20. CERVICAL MUCUS
CHANGES
 Changes in cervical mucus takes place over the
course of the menstrual cycle.
 During the menstrual phase the mucosa of cervix
does not undergo shedding off like endometrium.
 As proliferative phase begins the cervix begins to
produce a thin watery alkaline secretions .
 At the time of ovulation the cervical mucus is
thinnest and its elasticity is maximum. .

21. Contd…
 It can be stretched like a long thin elastic thread upto 8
to 12 cm . This is called Spinnbarkeit Effect . This
nature of cervical mucus favours the tansport of
sperms in the female genital tract and makes the
condition favourable for fertilization .
 After ovulation cervical secretions decrease in quantity
and becomes thick . These changes make a plug and
prevent entry of sperm through cervical canal .