FEMALE REPRODUCTIVE PHYSIOLOGY .pdf

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Female Reproductive Anatomy
▪ Ovaries are the primary female
reproductive organs
▪ Make female gametes (ova)
▪ Secrete female sex hormones (estrogen and
progesterone)
▪ Accessory ducts include uterine tubes, uterus,
and vagina
▪ Internal genitalia – ovaries and the internal ducts
▪ External genitalia – external sex organs

Reproductive Anatomy of the Human Female
External reproductive structures:
• labia
• clitoris
• vaginal opening
Internal reproductive structures:
• ovaries
• fallopian tube (uterine tube)
• cervix
• uterus
• vagina
• fimbrae

endometrium
myometrium
perimetrium

The Ovaries
▪ Paired organs on each side of the uterus held in
place by several ligaments
▪ Ovarian – anchors the ovary medially to the
uterus
▪ Suspensory – anchors the ovary laterally to the
pelvic wall
▪ Mesovarium – suspends the ovary in between
▪ Broad ligament – contains the suspensory
ligament and the mesovarium

The Ovaries
Figure 27.14a

Ovaries
▪ Blood supply – ovarian arteries and the
ovarian branch of the uterine artery
▪ They are surrounded by a fibrous tunica
albuginea, which is covered by a layer of
epithelial cells called the germinal
epithelium
▪ Embedded in the ovary cortex are ovarian
follicles

Ovaries
▪ Each follicle consists of an immature
germ cell called an oocyte
▪ Cells around the oocyte are called:
▪ Follicle cells (one cell layer thick)
▪ Granulosa cells (when more than one
layer is present)

Ovaries
▪ Primordial follicle – one layer of
squamouslike follicle cells surrounds
the oocyte
▪ Primary follicle – two or more layers
of cuboidal granulosa cells enclose the
oocyte
▪ Secondary follicle – has a fluid-filled
space between granulosa cells that
coalesces to form a central antrum

Ovaries
▪ Graafian follicle – secondary follicle at
its most mature stage that bulges from
the surface of the ovary
▪ Ovulation – ejection of the oocyte from
the ripening follicle
▪ Corpus luteum – ruptured follicle after
ovulation

Ovaries
Figure 27.12

Uterine Tubes (Fallopian Tubes) and Oviducts
▪ Receive the ovulated oocyte and provide a
site for fertilization
▪ Empty into the superolateral region of the
uterus via the isthmus
▪ Expand distally around the ovary forming
the ampulla
▪ The ampulla ends in the funnel-shaped,
ciliated infundibulum containing fingerlike
projections called fimbriae

Uterine Tubes
▪ The uterine tubes have no contact with
the ovaries and the ovulated oocyte is
cast into the peritoneal cavity
▪ Beating cilia on the fimbriae create
currents to carry the oocyte into the
uterine tube
▪ The oocyte is carried toward the
uterus by peristalsis and ciliary action

Uterine Tubes
▪ Nonciliated cells keep the oocyte and
the sperm nourished and moist
▪ Mesosalpinx – visceral peritoneum
that supports the uterine tubes

Uterus
▪ Hollow, thick-walled organ located in the
pelvis anterior to the rectum and
posterosuperior to the bladder
▪ Body – major portion of the uterus
▪ Fundus – rounded region superior to the
entrance of the uterine tubes
▪ Isthmus – narrowed region between the
body and cervix

Uterus
▪ Cervix – narrow neck which projects into the
vagina inferiorly
▪ Cervical canal – cavity of the cervix that
communicates with:
▪ The vagina via the external os
▪ The uterine body via the internal os
▪ Cervical glands secrete mucus that covers the
external os and blocks sperm entry except during
midcycle

The Ovaries

The Uterus
• harbours the embryo
• provides nutrients
• expels the fetus at the end of its development

Uterine Wall
▪ Composed of three layers
▪ Perimetrium – outermost serous
layer; the visceral peritoneum
▪ Myometrium – middle layer;
interlacing layers of smooth muscle
▪ Endometrium – mucosal lining of the
uterine cavity

Endometrium
▪ Has numerous uterine glands that change in length
as the endometrial thickness changes
▪ Stratum functionalis:
▪ Undergoes cyclic changes in response to ovarian
hormones
▪ Is shed during menstruation
▪ Stratum basalis:
▪ Forms a new functionalis after menstruation ends
▪ Does not respond to ovarian hormones

Uterine Vascular Supply
▪ Uterine arteries – arise from the internal iliacs,
ascend the sides of the uterus and send branches
into the uterine wall
▪ Arcuate arteries – branches of the uterine
arteries in the myometrium that give rise to
radial branches
▪ Radial branches – descend into the endometrium
and give off:
▪ Spiral arteries to the stratum functionalis
▪ Straight arteries to the stratum basalis

Uterine Vascular Supply
▪ Degeneration and regeneration of
spiral arteries causes the functionalis
to shed during menstruation
▪ Veins of the endometrium are thin-
walled with occasional sinusoidal
enlargements

Uterine Wall

Vagina
▪ Thin-walled tube lying between the bladder
and the rectum, extending from the cervix
to the exterior of the body
▪ The urethra is embedded in the anterior
wall
▪ Provides a passageway for birth, menstrual
flow, and is the organ of copulation

Vagina
▪ Wall consists of three coats: fibroelastic
adventitia, smooth muscle muscularis, and
a stratified squamous mucosa
▪ Mucosa near the vaginal orifice forms an
incomplete partition called the hymen
▪ Vaginal fornix – upper end of the vagina
surrounding the cervix

Vagina

External Genitalia: Vulva (Pudendum)
▪ Lies external to the vagina and includes the mons
pubis, labia, clitoris, and vestibular structures
▪ Mons pubis – round, fatty area overlying the
pubic symphysis
▪ Labia majora – elongated, hair-covered, fatty
skin folds homologous to the male scrotum
▪ Labia minora – hair-free skin folds lying within
the labia majora; homologous to the ventral penis

Accessory glands
- opening into the vestibule or lower vagina.
- keep the vagina moist and provide most of the
lubrication for intercourse.

A.Oogenesis
1. Egg production is called oogenesis,
which is a distinctly cyclic event.
2. Most primary oocytes undergo a
process of degeneration called atresia.
Only 2 million remain at the time of birth,
and by puberty, only 400,000 remain.
OOGENESIS

Oogenesis
▪ Production of female sex cells by meiosis
▪ In the fetal period, oogonia (2n ovarian stem
cells) multiply by mitosis and store nutrients
▪ Primordial follicles appear as oogonia are
transformed into primary oocytes
▪ Primary oocytes begin meiosis but stall in
prophase I

Oogenesis: Puberty
▪ At puberty, one activated primary oocyte produces two
haploid cells
▪ The first polar body
▪ The secondary oocyte
▪ The secondary oocyte is arrested in metaphase II and is
ovulated
▪ If penetrated by sperm cell, the second oocyte completes
meiosis II, yielding:
▪ One large ovum (the functional gamete)
▪ A tiny second polar body

3. Begining in adolescence, FSH stimulates the
primary oocytes to complete meiosis I, which
yields two haploid daughter cells of unequal size.
One will become the egg (20 oocyte) with large
amounts of cytoplasm. The other, a polar body, will
serve only as a dumping ground for the extra set of
chromosomes.
The secondary oocyte proceeds as far as
metaphase II and then arrested until
ovulation. If it is fertilized, it completes
meiosis II and produces a second polar
body. The large remaining egg unites its
chromosomes with those of the sperm and
produces a zygote.

Events of Oogenesis

Changes in the ovaries constitute the
ovarian cycle which is subdivided into 3
phases: the follicular phase, ovulation, and
luteal phase.
The parallel changes in the uterus are
called the menstrual or uterine cycle, which
is subdivided into 3 phases: menstruation,
proliferative phase, and secretory phase.
OVARIAN CYCLE

Follicular Phase
▪ The primordial follicle, directed by the
oocyte, becomes a primary follicle
▪ Primary follicle becomes a secondary
follicle
▪ The theca folliculi and granulosa cells
cooperate to produce estrogens
▪ The zona pellucida forms around the
oocyte
▪ The antrum is formed

Follicular Phase
▪ The secondary follicle becomes a vesicular
follicle
▪ The antrum expands and isolates the
oocyte and the corona radiata
▪ The full size follicle (vesicular follicle)
bulges from the external surface of the
ovary
▪ The primary oocyte completes meiosis I,
and the stage is set for ovulation

1) The Follicular Phase (Day 1-14)
The follicular phase extends from the beginning of
menstruation until ovulation. It averages 14 days,
but is also the most variable portion of the cycle.
FSH causes follicular cells around the oocyte to
develop into granulosa cells, and the follicle is now
a primary follicle.
Granulosa cells secrete an estrogen-rich follicular
fluid, which pools to form the antrum. The follicle is
now called the secondary follicle.
One follicle rapidly outpaces the others and
becomes the dominant follicle.

Ovarian Cycle

Ovulation
▪ Ovulation occurs when the ovary wall
ruptures and expels the secondary
oocyte
▪ Mittelschmerz – a twinge of pain
sometimes felt at ovulation
▪ 1-2% of ovulations release more than
one secondary oocyte, which if
fertilized, results in fraternal twins

2) Ovulation (Day 14)
Ovulation is triggered by a sudden
burstlike release of LH (Luteining
Hormone) secretion from pituitary when
estrogen rises beyond a critical
concentration.
The LH surge is the consequence of an
exceptional positive feedback of estrogen
on hypothalamus-pituitary axis.
Only the oocyte in the dominant follicle is
released in each ovarian cycle.
Oocytes in other follicles degenerate.

Luteal Phase
▪ After ovulation, the ruptured follicle collapses,
granulosa cells enlarge, and along with internal
thecal cells, form the corpus luteum
▪ The corpus luteum secretes progesterone and
estrogen
▪ If pregnancy does not occur, the corpus luteum
degenerates in 10 days, leaving a scar (corpus
albicans)
▪ If pregnancy does occur, the corpus luteum
produces hormones until the placenta takes over
that role (at about 3 months)

Corpus luteum also secretes inhibin
at this point, which suppresses FSH
and further ovulations.
In the absence of pregnancy the
corpus luteum begins to degenerate
in about 10 days because rising
progesterone output inhibits further
release of FSH and LH.
Without LH, the corpus luteum begins
to shrink.

If pregnancy occurs, the corpus luteum
continues to secrete progesterone and
estrogen for about 3 months under the
stimulation of LH-like hormone
released by the developing embryo.
The secretion by corpus luteum does
not stop until the placenta is ready to
take over its homone-producing duties.
This is known as corpus luteum
rescue.

Establishing the Ovarian Cycle
▪ During childhood, ovaries grow and secrete
small amounts of estrogens that inhibit the
hypothalamic release of GnRH
▪ As puberty nears, GnRH is released; FSH
and LH are released by the pituitary, which
act on the ovaries
▪ These events continue until an adult cyclic
pattern is achieved and menarche occurs

Feedback Mechanisms in Ovarian
Function
Figure 27.21

Hormone
Fluctuation

Ovarian Cycle - Luteal Phase
▪ Corpus luteum - forms from ruptured follicle, under influence of LH;
secretes progesterone

The Uterine
Cycle

Menstrual (Uterine) Cycle
1) Menstruation (Day 1-5)
The superficial layer stratum
functionalis of the uterus detaches
from the uterine wall, accompanied by
bleeding for 3-5 days.
Sex hormones are at their lowest
normal levels at Day 1
Menstrual fluid contains fibrolysin,
therefore it normally does not clot.

2) Proliferative Phase (Day 6-14)
Estrogen stimulates mitosis, the prolific growth of
blood vessels, and the formation of a new stratum
functionalis.
Estrogen also stimulates the endometrium to
develop progesterone receptors.
As ovulation approaches, the uterine tube becomes
edematous, its fimbriae develop and caress the
ovary, and its cilia create a gentle current in the
nearby peritoneal fluid.

The ovulated egg is usually caught up in this current and
swept into the tube.
An oocyte has only 24 hours to be fertilized.
The chance of fertilization is enhanced by changes in the
cervical mucus at the time of ovulation.
It becomes thinner and more stringy.

Menstrual Cycle - Proliferative
Phase
▪ Day 6-14 rebuild endometrial tissue
▪ mitosis occurs in stratum basalis
▪ result of estrogen from developing follicles

3) Secretory Phase (Day 15-28)
a. In response to rising level of
progesterone, the endometrium of the
uterus proliferates further in preparation for
possible pregnancy.
Spiral arteries elaborate and coil more
tightly
Uterine glands enlarge, coil, and begin
secreting nutritients into the uterine cavity
to sustain the embryo until implantation.
The cervical mucus becomes viscous,
forming the cervical plug, which prevents
sperm entry.

▪ Further thickening of endometrium due to secretion and fluid
accumulation -- not mitosis
▪ Due to progesterone stimulation of glands
Menstrual Cycle - Secretory Phase

If pregnancy does not occur towards
the end of the secretory phase, LH
level drops due to negative feedback
of high level of progesterone.
Progesterone level decline following
the drop of LH. Without the support
of progesterone, the endometrium
undergoes degeneration in the
following sequence.

The spiral arteries close due to continuous
and intensive constriction (spasm).
The superficial layer stratum functionalis of
the uterus is deprived of blood supply.
The endometrial cells die of ischemia.
The spiral arteries suddenly relax and open
wide.
Blood gushes into the weakened capillary
beds, causing the capillaries to fragment
and the stratum functionalis to slough off.

Menstrual Cycle Premenstrual
Phase
▪ Involution of corpus luteum, progesterone falls
▪ spiral arteries constrict causes endometrial ischemia
▪ stratum functionalis sloughs

Menstrual Cycle - Menstrual
Phase
▪ Blood, serous fluid and endometrial tissue are discharged

Menses
▪ If fertilization does not occur, progesterone levels fall,
depriving the endometrium of hormonal support
▪ Spiral arteries kink and go into spasms and endometrial
cells begin to die
▪ The functional layer begins to digest itself
▪ Spiral arteries constrict one final time then suddenly
relax and open wide
▪ The rush of blood fragments weakened capillary beds
and the functional layer sloughs

▪ c. The menstrual cycle starts over again on this
first day of vaginal discharge.

Figure 27.22a, b
Gonadotropins, Hormones, and the Ovarian
and Uterine Cycles

Figure 27.22c, d
Gonadotropins, Hormones, and the Ovarian
and Uterine Cycles

▪ Estrogen levels rise during puberty
▪ Promote oogenesis and follicle growth in the ovary
▪ Exert anabolic effects on the female reproductive
tract
▪ Uterine tubes, uterus, and vagina grow larger and
become functional
▪ Uterine tubes and uterus exhibit enhanced motility
▪ Vaginal mucosa thickens and external genitalia
mature
Extrauterine Effects of
Estrogens and Progesterone

▪ Growth of the breasts
▪ Increased deposition of subcutaneous fat,
especially in the hips and breasts
▪ Widening and lightening of the pelvis
▪ Growth of axillary and pubic hair
▪ Stimulate bone growth
▪ Increases HDL and lowers LDL
Estrogen-Induced Secondary Sex
Characteristics

FERTILIZATION
▪The fusion of sperm cell
nucleus and an egg cell
nucleus is known as
fertilization. This process
takes place in the distal
portion of the uterine tube
called the ampulla.
▪ The fertilized egg is now
refered to as a zygote.
▪The appropriate number
of chromosomes has also
been restored.
This process takes place
within 48hrs of ovulation .
Once the sperm cell
penetrate the ovum, the
2nd polar body is extruded
and the fertilized ovum
begins to divide.

Accomplishing Fertilization
▪ The oocyte is viable for 12 to 24 hours
▪ Sperm is viable 24 to 72 hours
▪ For fertilization to occur, coitus must occur no
more than:
▪ Three days before ovulation
▪ 24 hours after ovulation
▪ Fertilization – when a sperm fuses with an egg
to form a zygote

Sperm Transport and Capacitation
▪ Fates of ejaculated sperm
▪ Leak out of the vagina immediately after
deposition
▪ Destroyed by the acidic vaginal environment
▪ Fail to make it through the cervix
▪ Dispersed in the uterine cavity or destroyed by
phagocytic leukocytes
▪ Reach the uterine tubes
▪ Sperm must undergo capacitation before they
can penetrate the oocyte

Acrosomal Reaction and Sperm Penetration
▪ An ovulated oocyte is encapsulated by:
▪ The corona radiata and zona pellucida
▪ Extracellular matrix
▪ Sperm binds to the zona pellucida and
undergoes the acrosomal reaction
▪ Enzymes are released near the oocyte
▪ Hundreds of acrosomes release their
enzymes to digest the zona pellucida

▪Once a sperm makes contact
with the oocyte’s membrane:
▪Beta protein finds and binds to
receptors on the oocyte
membrane
▪Alpha protein causes it to insert
into the membrane

Figure 28.2a

Blocks to Polyspermy
▪ Only one sperm is allowed to penetrate the oocyte
▪ Two mechanisms ensure monospermy
▪ Fast block to polyspermy – membrane
depolarization prevents sperm from fusing with
the oocyte membrane
▪ Slow block to polyspermy – zonal inhibiting
proteins (ZIPs):
▪ Destroy sperm receptors
▪ Cause sperm already bound to receptors to
detach

IMPLANTATION
▪ The zygote passes down the fallopian tube
and enters into the uterus.
▪ Continuous cell divisions result in the
formation of a hollow ball of cells called a
blastocyst.
▪ The zygote obtains nutrients from fluids
secreted by the mother.
▪ On the sixth day, the zygote/ball of cells
implants in the uterine wall.

Implantation
▪ Viability of the corpus luteum is maintained by
human chorionic gonadotropin (hCG) secreted by
the trophoblasts.
▪ HCG prompts the corpus luteum to continue to
secrete progesterone and estrogen
▪ Chorion – developed from trophoblasts after
implantation, continues this hormonal stimulus
▪ Between the second and third month, the placenta:
▪ Assumes the role of progesterone and estrogen
production
▪ Is providing nutrients and removing wastes

PREGNANCY
▪ Pregnancy – events that occur from fertilization until
the infant is born
▪ Conceptus – the developing offspring
▪ Gestation period – from the last menstrual period
until birth
▪ Preembryo – conceptus from fertilization until it is
two weeks old
▪ Embryo – conceptus during the third through the
eighth week
▪ Fetus – conceptus from the 9th wk till birth

EVENTS OF EARLY PREGNANCY
EVENT DAYS AFTER
OVULATION
OVULATION 0
FERTILIZATION 1-2
BLASTOCYSTS enters uterine
cavity
4
IMPLANTATION 5
TROPHOBLAST forms and
attaches to endometrium
6
TROPHOBLAST begins to
secreteHCG
8
HCG rescues corpus luteum 10

EMBRYONIC DEVELOPMENT
▪The zygote undergoes a series of rapid mitotic cell
divisions called cleavage.
▪The process begins by the zygote dividing into two
identical cells, followed by four, then eight, ect.
▪Three cell layers are formed and are called primary
germ layers.
▪This begin the process of forming all the tissues,
organs and systems in an animal and is known as
differentiation.

Human Reproductive Process
▪The developing embryonic
membranes become part of the
placenta and umbilical cord.
▪After eight weeks of
development the embryo is
called the fetus.
▪The period of time between
fertilization and birth is called
gestation.
▪Gestation in humans usually
lasts nine months or
approximately 266 days.

PREGNANCY HORMONES
▪ 1ST TRIMESTER – HCG,
PROGESTERONE,OESTROGEN, RELAXIN.
▪ 2ND TRIMESTER – HPL, STEROID
HORMONES
▪ 3RD TRIMESTER – CROSSOVER OF
OESTROGEN, HPL, PROLACTIN, RELAXIN

Hormonal Changes During Pregnancy
Figure 28.6

PARTURITION
▪ The delivery of the foetus – 40weeks after the onset
of the last menstrual period.
▪ Once the foetus reaches a critical size, ditention of
the uterus increases contractility
▪ Uncoordinated contractions known as Braxton
Hicks contractions begins- about a month before
parturition
▪ Oestrogen/progesterone ratio increases which
increases the sensitivity of of the uterus to
contracting stimuli

Parturition..........
▪ Oestrogen stimulates local
production of prostaglandins
which increases the intracellular
Ca++ concentration of uterine
smooth muscle. Also, increases the
sensitivity of oxytocin receptors.
▪ Oxytocin stimulates powerful
uterine contraction

Parturition: Initiation of Labor
Figure 28.16

3 Stages of labour
▪ Ist stage: uterine contractions originating
at the fundus and sweeping downwards
move the head of the foetus toward the
cervix and progressively widens the cervix
▪ 2nd stage: the foetus is forced through the
cervix and delivered per vagina
▪ 3rd stage: the placenta separates from the
uterine decidual tissue and its delivered.

83
Lactation
▪ Physiology of lactation
▪ Changes during pregnancy
▪ Increased breast tissue
▪ Maturation of structure
▪ Hormonal controls
▪ Prolactin: stimulates milk production
▪ Oxytocin: stimulates milk release
▪ “let-down” reflex

84

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