 REPRODUCTION SERIES 2

Prof O.I. Ajayi

 Physiological Stages
• Neonatal period: birth---4 weeks
• Childhood: 4 weeks----12 years
• Puberty: 12 years---18 years
• Sexual maturation: 18 year---50 year
• Perimenopause: decline of ovarian function (40 years)----1
year postmenopause
• Postmenopause:
 Menstruation
• Menstruation
cyclic endometrium sheds and bleeds due to cyclic
ovulation
• Mense
1. Endometrium is sloughed (progesterone withdrawal)
2. Nonclotting menstrual blood mainly comes from artery
(75%)
3. Interval: 24-35 days (28 days). duration: 2-6 days. the
first day of menstrual bleeding is considered as day 1
4. Shedding: 30-50 ml
Principal organs of the female reproductive system

•Ovaries
•Uterine tubes
•Uterus
•Vagina
Female Reproductive system
• 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
 BiologyReproductive
Female 100 System
Human Biology
uterine tube fimbriae
ovary
uterus
bladder
cervix
urethra
clitoris
vagina
l. minora
l. majora
vaginal orifice
The Ovaries and Their Relationships to the
Uterine Tube and Uterus
 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
Ovary

1) produce oocyte (oogenesis)

- 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.
- Normally, only one oocyte is ovulated each 28-day
Ovary

1) produce oocyte (oogenesis)

2) produce hormone
estrogens, progesterone, inhibin, and a
small amount of androgen.
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
The Ovaries
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
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 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
The Uterine vascular supply
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
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
- stratified squamous epithelium.
- Bacteria ferment glycogen to lactic acid, resulting
in a low vaginal pH.
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.
OOGENESIS
• 1. Egg production is called oogenesis which is distinctly a cyclic event.
• 2. most primary oocytes undergo a process of degeneration called
Atresia
• 3. only 2million remain at birth and at puberty, just about 400,000
remains out of which functional ones that are ovulated are just 400
with thousand degenerating with each cycle.
 Oogenesis -1
•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 and
are transformed into primary oocytes
•Primary oocytes begin meiosis but stall in
prophase I until puberty.
 Oogenesis: Puberty - 2
• 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 the secondary 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 ovum (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 ovum unites its chromosomes with

those of the sperm cell and produces a zygote.
Events of Oogenesis
OVARIAN CYCLE
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.
 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
 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
 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
 Luteal phase …
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.

 Luteal phase …
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.
Proliferative phase…

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)
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.
Menstrual Cycle - Secretory Phase

• Further thickening of endometrium due to secretion and fluid

accumulation -- not mitosis
• Due to progesterone stimulation of glands
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 the weakened capillary beds and the
functional layer sloughs
• c. The menstrual cycle starts over again on this
first day of vaginal discharge.
Gonadotropins, Hormones, and the Ovarian and
Uterine Cycles

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

Figure 27.22c, d
 Extrauterine Effects of Estrogens and
Progesterone
• 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
Estrogen-Induced Secondary Sex Characteristics
• 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
 The hormone cycle

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings