Female Reproductive Physiology
and Menstrual cycle
Lecture 4
Dr. Zahoor
Dr. Shaikh Mujeeb Ahmed
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Objectives
•
•
•
•
Oogenesis and the stages of follicle development
Ovulation and formation of corpusluteum
Ovarian cycle
Secretion of FSH and LH through negative and
positive feedback mechanisms during a
menstrual cycle
• Uterine cycle
• Draw a diagram and show changes in FSH, LH,
estradiol, progesterone, and correlate these with
ovarian and uterine changes during the
menstrual cycle
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Female Reproductive Physiology
• Characterized by complex cycling
• Ovaries
– Primary female reproductive organs
• Produce ova (oogenesis)
• Secrete female sex hormones
– Estrogen (estradiol)
– progesterone
3
Female Sex Hormones
–These are steroid hormone
–Estrogen
» Maturation and maintenance of entire female
reproductive system .
» Essential for ova maturation and release
» Establishment of female secondary sexual
characteristics
» Essential for transport of sperm from vagina to
fertilization site in oviduct
» Contributes to breast development in
anticipation of lactation
–In general action of estrogen is important
in preconception events
4
Female Sex Hormones
–Progesterone
» Important in preparing suitable environment for
nourishing a developing embryo/fetus
» Contributes to breasts’ ability to produce milk
–In general progesterone is important in
post conception events
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OOGENESIS [GAMETOGENENSIS]
• Formation of Primary oocytes from oogonium
is completed before birth, 6-7 million oogonia
by the fifth month of gestation. Soon Atresia
starts and the number starts reducing.
• After birth the number is reduced to 2 million
(No new oocyte appear after birth )
• At puberty – 300, 000 -- oogonia present.
• During reproductive age only 400-500 ova
mature and ovulate .
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Oogenesis
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OOGENESIS [GAMETOGENENSIS]
• The first meiotic division of primary oocyte
begins during embryonic life but is arrested at
prophase
• Primary oocyte remains in the state of meiotic
arrest for years and is completed only at
ovulation [Release of ovum from ovary] at
puberty.
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• At ovulation it forms Secondary Oocyte which
contains half the Chromosomes (22+x) and 1st
polar body which undergoes degeneration.
• The secondary oocyte then undergoes the 2nd
meiotic division but is arrested at metaphase,
and completed during fertilization.
• It form the mature ovum (22+x) and the 2nd
polar body.
• The second polar body too undergoes
degeneration
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Oogenesis
Spermatogenesis
• Identical steps of
chromosome replication and Accomplished within
two months
division during gamete
production in both sexes
– Timing and end result
are very different
Oogenesis
Take anywhere from
12 to 50 years to
complete on cyclic
basis from onset of
puberty until
menopause
Postpubertal male can
produce several
hundred million sperm
each day
Female born with
limited, largely
nonrenewable
supply of germ cells
Each primary
spermatocyte yields
four equally viable
spermatozoa
Each primary oocyte
yields only one
cytoplasm-rich ovum
and three
cytoplasm-poor
polar bodies that
disintegrate
Female reproductive system
• We will discuss
1. Ovarian cycle
2. Hormonal effects (hypothalamus & ant.
Pituitary)
3. Uterine or menstrual cycle
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1. Ovarian Cycle
•
•
•
•
Average ovarian cycle lasts 28 days
Normally interrupted only by pregnancy
Finally terminated by menopause
Ovarian cycle Consists of two alternating
phases
– Follicular phase(1-14 days )
• Dominated by presence of maturing follicles
– Luteal phase(15-28 days)
• Characterized by presence of corpus luteum
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Ovarian Cycle-Follicular phase
– Granulosa cells of some primary follicles
proliferate
– Theca cells proliferate (estrogen secreting
cells)
– Theca cells and Granulosa cells are
collectively known as follicular cells
– Under the effect of FSH 15-20 of the follicles
grow rapidly forming secondary follicle
which are capable of secreting estrogen
– Oocyte inside each follicle enlarges
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Ovarian Cycle-Follicular phase
– One follicle usually grows more rapidly and
mature (graafian follicle) about 14 days
after onset of follicular development
– Graafian follicle bulges on ovarian surface ruptures to release secondary oocyte from
ovary (ovulation)- facilitated by burst in LH
secretion
– Released oocyte enters oviduct where it
may or may not be fertilized
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Development of the Follicle, Ovulation, and Formation and
Degeneration of the Corpus Luteum
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Ovarian Cycle-Luteal phase
• Last 14 days of ovarian cycle
– The remnants of the ruptured graafian
follicle develop into Corpus luteum under
influence of LH (leuteinization)
– The granulosa cells are filled with yellowish
lipid- lutein.
– Becomes highly vascularized
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Ovarian Cycle-Luteal phase
– Corpus Luteum has endocrine functions and
it secretes progesterone & estrogen (more
of progesterone). It remains for 14 days
(14- 28 days ).
– If fertilization does not
occurs
degenerates into Corpus Albicans.
it
– If fertilization takes place it persists until
placenta is formed & secrete increase
quantity of progesterone & estrogen
(corpus luteum of pregnancy)
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Ovarian Cycle
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2. EFFECT OF PITUITARY
HORMONES ON OVARIAN CYCLE
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Regulation of Ovarian Cycle by hormonal interactions
1. During follicular phase, rise in FSH signals
ovarian follicle to secrete more estrogen
2. Rise in estrogen feeds back to inhibit FHS
secretion which declines as follicular phase
proceeds
3. LH rises in follicular phase
• As it peaks in mid-cycle, it triggers ovulation
4. Estrogen output decreases and mature
follicle is converted to a corpus luteum
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Regulation of Ovarian Cycle by hormonal interactions
5. Corpus luteum secretes progesterone and
estrogen during luteal phase
– Progesterone output inhibits release of FSH
and LH
• Low LH – corpus luteum degenerates
• Progesterone levels decline
6. FSH can start to rise again, initiating new
cycle
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Hormonal regulation of female
sexual cycles
Important keys about hypothalamo
hypophysial ovarian axis
• The
master key is the hypothalamic
factors which changes the rate of
secretion of anterior pituitary
• Pituitary hormones affects the rate of
ovarian hormones secretion through the
ovarian cycle.
• Cyclic
Changes in ovarian hormones
produces cyclic changes in uterus
(menstrual cycle), breast, and other
secondary sex organs
• As long as there is high level of estrogen
(E) & progesterone (P), the endometrium is
maintained without menstruation (as
during pregnancy)
• So, for menstruation to occur, there must
be a period of high (E) & (P) (to

thickness (prepare) the uterus followed by
sudden (abrupt)  in their levels as during:
1. Normal menstrual period
2. Intake of contraceptive pills (which
contain high
E & P; menstruation
occurs only after stop of pills)
Relationship between pituitary
gonadotropins & ovarian hormones (E & P)
• Usually –ve feedback mechanism (E & FSH)
(P & LH) except when there is a very high
estrogen levels (it becomes + ve feedback
(at ovulation time)
SO that:
• At the end of previous cycle and start of
new cycle, there in E & P plus inhibin
hormones
(caused by degeneration of
corpus luteum (CL) and in FSH (w
stimulate growth of new follicles)
• After 5 days, the growing follicles will
secrete estrogen that will inhibits FSH
• At
12 days, estrogen is markedly
increased, making +ve FB on pituitary
caused marked increased in LH (LH surge)
and FSH. Both will induce ovulation.
• After ovulation (after day 14), the formed
CL will secrete high amount of E & P
(mainly
progesterone)
plus
inhibin
hormone (the 3 hormones are secreted
from lutein cells)
• E , P, &
inhibin hormones from CL will
inhibit FSH, LH then:
a. If no fertilization occur, CL will
degenerate   (E & P) degeneration
of endometrium; new menstrual cycle
(note:
menstrual
cycle
starts
by
menstruation)
b. If fertilization occurs, CL will grow (CL of
pregnancy) till 4th month when placenta
is formed; both of them will maintain
high E & p maintain endometrium and
pregnancy
28 1
5
12
14
Follicular phase
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28 1
26
28 1
26
28 1
Luteal phase
FSH
28 1
5
12
14
Estrogen
Ovulatory phase
28 1
5
12
5
12
5
12
14
Progesterone
28 1
28 1
14
26
28 1
LH
14
26
28 1
28 1
5
12
14
Follicular phase
26
28 1
Luteal phase
FSH
28 1
1
5
12
14
26
28
Estrogen
Ovulatory phase
28 1
5
12
5
12
5
12
14
26
28 1
26
28 1
Progesterone
28 1
28 1
14
LH
14
26
28 1
Production of estrogen by ovarian follicle
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3. Uterine Cycle / Menstrual cycle
• Reflects hormonal changes during ovarian cycle
• Averages 28 days
• Outward manifestation of cyclic changes in uterus
is menstrual bleeding once during each cycle
• Consists of three phases
– Menstrual phase (3-5days)
– Proliferative phase (6-14 days)
– Secretory or progestational phase (15-28 days)
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• Estrogen stimulates growth
of both endometrium and
myometrium .
• It also induces synthesis of
progesterone receptors in
endometrium.
• Progesterone: make
endometrial connective
tissue loose and
edematous
• Growth of endometrial
blood vessels and glands
to secrete glycogen
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Uterine Cycle-Menstrual phase
– 3-5 days of cycle
– Characterized by discharge of blood and
endometrial debris from vagina
– First day of menstruation is considered start
of new cycle
– Coincides with end of ovarian luteal phase
and onset of follicular phase
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Uterine Cycle-Menstrual phase
– As corpus luteum degenerates the level of
progesterone & estrogen drops that results in Release of uterine prostaglandin
• Causes vasoconstriction of endometrial vessels
– Disrupts blood supply
– Causes death of endometrium
• Stimulates mild rhythmic contractions of
uterine myometrium
– Help expel blood and endometrial debris from
uterine cavity out through vagina (menstrual flow)
• Bleeding lasts for 3-5 days, 30-150 ml of blood is lost
per cycle. Fibrinolysins are present which dissolves
any clots.
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Uterine Cycle
• Proliferative phase (6-14days)
– Begins concurrent with last portion of ovarian
follicular phase
• Endometrium starts to repair itself and proliferate
under influence of estrogen from newly growing
follicles
• Glands and arteries proliferate and there is increases
thickness of endometrium
– Estrogen-dominant proliferative phase lasts from
end of menstruation to ovulation
– Peak estrogen levels trigger LH surge responsible
for ovulation
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Uterine Cycle
Secretory or progestational phase(15-28day)
– Uterus enters this phase after ovulation when new
corpus luteum is formed
– Corpus luteum secretes large amounts of
progesterone and estrogen
• Under effect of Progesterone
– The endometrium grows further in thickness with
increase in secretions of glands and arteries become
more coiled
– The secretion are rich in electrolytes, enzymes and
glycogen which provide nourishment to the developing
embryo before implantation, if fertilization has taken
place.
– If fertilization and implantation does not occur
• Corpus luteum degenerates
• New follicular phase and menstrual phase begin once again 38
Various factors can disrupt the menstrual
cycle
• Weight loss/low body
weight
• Disordered eating
• Vigorous physical
activity
• Stress
Athletic Menstrual Irregularities (AMI )
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•
•
•
Amenorrhea ( Cessation of Menstrual periods)
Oligomenorrhea (Less flow, irregular)
Anovulatory cycle
In general population menstrual cycle
dysfunction occurs – 2-5%
• But survey done in Athlete(Daily 3.5 hours of
moderate intensity sports) showed Menstrual
cycle irregularity 2-51%
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AMI (C0NT)
• MECHANISM RESPONSIBLE
• Rapid loss of weight , decreased body fat, dietary
insufficiencies. Stress, intensity of training, age at
onset of training.
• Hormonal changes responsible
– FSH-LH environment totally unbalanced ,
– Decreased estrogen in follicular phase
– Decreased progesterone in luteal phase
IMPORTANT- All women athlete returned to normal
within 6 months after training
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THANK YOU
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