The document discusses the menstrual cycle, a complex process in females, averaging 28 days, characterized by hormonal interactions leading to the shedding of the uterine lining if fertilization does not occur. It outlines the hormonal control via the hypothalamo-pituitary-ovarian axis, detailing the roles of FSH, LH, and estrogen during different phases of the cycle, including ovulation and the formation of the corpus luteum. The menstrual cycle culminates in menstruation if no pregnancy occurs, marked by a decline in estrogen and progesterone.

1. MENSTRUAL CYCLE
Dept. of Zoology

2. ● There are two type of reproductive cycles:
● Menstrual Cycle and Estrous cycle.
● Estrous cycle is reproductive cycle of female of non primates.
● Menstrual cycle is reproductive cycle of female of humans and old world
monkeys.
Reproductive Cycle

3. The Menstrual Cycle: An Overview
● The menstrual cycle is a complex process that occurs in the female body,
lasting an average of 28 days.
● It involves the release of hormones from the brain and ovaries, which leads
to the shedding of the uterine lining if fertilization does not occur.
● The first menstrual cycle, or first menstrual bleeding, in female humans is
known as Menarche.
● The time that marks the end of female menstrual cycles is menopause.

4. Hormonal control :
Hypothalamo - pituitary - ovarian axis
● Cycle is controlled by
hypothalamus.
● In females at age of 10-12 years,
Hypothalamus releases
Gonadotropin releasing hormone
(GnRH) which command to
anterior pituitary gland to release
LH and FSH.
● FSH > LH in females.
● LH > FSH in males.
Principle of anatomy and physiology by Gerald J. Tortora &
Bryan Derrickson. 12th edition, Ch-28- (pg. No.1098)

5. ● In ovaries there are primordial follicle or
Primary Follicle which have oogonium
inside and spindle cell on outside.
● Spindle cell helps in nourishment of cell
and produce MIF.
● Spindle cells has the receptor of FSH.
oogonium
Primary Follicle

6. ● FSH binds to spindle cells and change it
behavior and stop MIF production. Now
oogenesis continues.
● Spindle cell under influence of FSH starts
producing Estrogen.
● Estrogen binds on spindle cells and
spindle cells starts dividing.
● Multiple spindle cells knows as
Granulosa cells.

7. ● As FSH leads to release of estrogen so at is beginning of female reproduction cycle
known as Menarche event
● Now, menstrual cycle begin and Menstrual cycle runs for 28 day but also for 35 - 42
days in rare case)

8. Beginning of Cycle
● FSH is important for initiation of
menstrual cycle so, Initially Estrogen
increases.
● When FSH bind at spindle cells, the
cells produce estrogen.
Textbook of Medical Physiology by Arthur C. Guyton & M.D. John E. Hall, Ph.D.
11
th edition, Ch-81, (pg. No. 1013)

9. 0-4 Days Ovarian Cycle
● In both ovaries 4 to 5 follicle are present, but 8 to 10 follicle start
developing simultaneously.
● Out of 8-10 follicle ,Single dominant follicle is selected and rest
will degenerate.
● FSH is responsible for selecting dominant follicle.
● Estrogen level start to rise as follicular development occurs.

10. At 6,7,8,9,10 Days in Ovary
● The selected follicle is
developed.
● When granulosa cell
produce Estrogen,
Estrogen increase and
some of estrogen stored
in a cavity called as
Antrum.
● Now follicle is known as
Secondary follicle.
https://www.gettyimages.co.uk/photos/antrum
Antrum
Primary
Oocyte
Granulosa
cell

11. ● At 9 & 10 day follicle
enlarged.
● At this stage certain ovarian
cells start surrounding
follicle.
● Follicle size increase and
added layers called theca
interna and Theca Externa.
https://commons.wikimedia.org/wiki/File:Graafian_follicle.jpg

12. Day 10-12
● During this time Estrogen reach it peak
● When estrogen was rising it were
showing negative feedback for FSH &
LH.
● When Estrogen concentration is at
peak it shows positive feedback for
FSH & LH.
● Now, LH & FSH surge.
Textbook of Medical Physiology by Arthur C. Guyton & M.D. John E. Hall, Ph.D.
11
th edition, Ch-81, (pg. No. 1013)

13. ● Just before 14th day there is high LH
concentration.
● Due to high LH concentration the estrogen
secreting cell i.e., Granulosa now
converted into Progesterone Secreting
Cell.
● At 12 day Estrogen feedback change
negative to positive so this lead to LH
surge & LH peak tells granulosa to secrete
progesterone in place of estrogen.
● So LH stimulation is responsible for
progesterone release.
Textbook of Medical Physiology by Arthur C. Guyton & M.D. John E. Hall, Ph.D.
11
th edition, Ch-81, (pg. No. 1013)

14. Day 14 Ovulation
● Ovulation means release of
secondary oocyte.
● LH cause ovulation.
● When secondary oocyte release, it
release with a layer of granulosa
cells.
● These granulosa cells are releasing
Progesterone.
● Just before ovulation, follicle have
secondary oocyte, large antrum,
Granulosa cell form Progesterone.
● Now it is Mature follicle or Graafian
Follicle.
http://medcell.org/histology/female_reproductive_system_lab/graafian_follicle.php
Antrum
Granulosa Cell
Secondary Oocyte

15. ● Only single layer of granulosa cells come
out with secondary oocyte and remaining
one are still in the ovary.
● The one remaining in ovary are known as
Corpus hemorrhagicum.
● The theca externa release Protease, which
help in rupturing of ovarian wall.
Principle of anatomy and physiology by Gerald J. Tortora &
Bryan Derrickson. 12th edition, Ch-28- (pg. No.1100)

16. 16th to 17th Day
● Corpus hemorrhagicum becomes
Corpus luteum because of lipid
decomposition.
● Corpus Luteum is a transitory
endocrine gland formed.
● Corpus Luteum secrete estrogen and
progesterone, but Progesterone
secreted in more concentration than
estrogen.
● Corpus Luteum survive for 8-10 days
https://www.bu.edu/phpbin/medlib/histology/p/18204ooa.htm

17. After 24th day
● Corpus luteum starts regressing.
● That's why after 24th day Estrogen and
progesterone start decreasing.
● As, Estrogen and progesterone
decreased negative feedback also
disappeared thats why FSH & LH
increase.
● Surge in FSH initiates the next
menstrual cycle.
NCERT Class 12 Biology Book

18. Proliferative Phase
● On the 5 day of follicular phase the
estrogen starts increase its
concentration and on 12 day its
concentration at peak.
● During peak phase the estrogen acts on
the ovary as well as on the uterus.
● Endometrium growth take place.
NCERT Class 12 Biology Book

19. Secretion Phase
● Increase in LH stimulates the granulosa
cells to produce progesterone in place of
estrogen.
● The progesterone now initiates secretory
phase in the uterus.
● Now the endometrium starts secreting
certain Mucopolysaccharide.
● Due to progesterone there is expression
of carbohydrates which helps in
implantation.
● That's why progesterone is hormone of
implantation or pregnancy,

20. Day 24 & 25
● On 24 and 25 day there is decline in
progesterone and estrogen.
● This action cause disappear of
endometrium.
● Decline in progesterone & estrogen
cause regression of endometrium wall
as well as blood vessels in form of
blood.
● This blood is Arteria in nature.

21. Reference
● Principle of anatomy and physiology by Gerald J. Tortora & Bryan Derrickson. 12th
edition, Ch-28- (pg. No.1097), (pg. No.1140), (pg. No.1141).
● Textbook of Medical Physiology by Arthur C. Guyton & M.D. John E. Hall, Ph.D.
11th edition, Ch-81, (pg. No. 1012), (pg. No.1013), (pg. No.1014), (pg. No.1015).

22. Thank you