Transcript powerpoint lecture

Lecture 11
The Reproductive System
The Reproductive System
• Primary sex organs (gonads)
– testes and ovaries
• Produce gametes (sex cells ) – sperm & ova
• Secrete steroid sex hormones
– Androgens (males)
– Estrogens and progesterone (females)
• Accessory reproductive organs
– ducts, glands, and external genitalia
Male Reproductive System
• Testes produce sperm
• Sperm delivered to exterior through system of
ducts:
– Epididymis
– Ductus (vas) deferens
– Ejaculatory duct
– Urethra
Figure 27.1 Reproductive organs of the male, sagittal view.
Ureter
Peritoneum
Seminal gland
(vesicle)
Ampulla of
ductus deferens
Ejaculatory duct
Rectum
Prostate
Bulbo-urethral gland
Anus
Bulb of penis
Ductus (vas) deferens
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Epididymis
Testis
Scrotum
Urinary bladder
Prostatic
urethra
Pubis
Intermediate
part of the
urethra
Urogenital
diaphragm
Corpus
cavernosum
Corpus
spongiosum
Spongy
urethra
Glans penis
Prepuce
(foreskin)
External
urethral orifice
The Scrotum
• Contains paired testes
• Hangs outside abdominopelvic cavity
– Viable sperm cannot be produced at body temp.
– 3 C lower than core body temperature
– Lower temperature necessary for sperm
production
The Testes
• Each surrounded by two tunics
• Tunica vaginalis
– outer layer derived from peritoneum
• Tunica albuginea
– inner layer; fibrous capsule
• Septa divide testis into ~250 lobules, each containing
1–4 seminiferous tubules - site of sperm production
Figure 27.3a Structure of the testis.
Spermatic cord
Blood vessels
and nerves
Ductus (vas)
deferens
Head of epididymis
Testis
Efferent ductule
Seminiferous
tubule
Rete testis
Lobule
Septum
Tunica albuginea
Straight tubule
Body of epididymis
Duct of epididymis
Tail of epididymis
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Tunica vaginalis
Cavity of
tunica vaginalis
Seminiferous Tubule
• Thick, stratified epithelium surrounding
central fluid-containing lumen
• Epithelium contains:
– Spermatogenic cells
– Sustentocytes
– Myoid cells surround each tubule
Cells of the Testis
• Spermatogenic
– sperm forming cells
• Sustentocytes
– large columnar cells play a role in sperm
production
• Myoid
– layers of smooth muscle to move sperm out
Interstitial Cells
• Interstitial endocrine cells
– In soft tissue surrounding seminiferous tubules
• Produce androgens (testosterone)
– Secrete it into interstitial fluid
The Penis
• Spongy urethra and three cylindrical bodies of
erectile tissue
– spongy network of connective tissue and smooth
muscle with vascular spaces
• Corpus spongiosum
– surrounds urethra and expands to form glans and bulb
• Corpora cavernosa
– paired dorsal erectile bodies
Figure 27.5 Male reproductive structures.
Ureter
Urinary bladder
Ampulla of ductus deferens
Seminal gland
Prostate
Prostatic urethra
Ejaculatory duct
Orifices of prostatic
ducts
Intermediate part
of the urethra
(membranous urethra)
Urogenital diaphragm
Root of penis
Crus of penis
Bulbo-urethral gland and duct
Bulb of penis
Bulbo-urethral duct opening
Ductus deferens
Corpora cavernosa
Epididymis
Body (shaft)
of penis
Corpus spongiosum
Testis
Section of (b)
Spongy urethra
Glans penis
Prepuce (foreskin)
External urethral orifice
Dorsal vessels
and nerves
Corpora cavernosa
Urethra
Skin
Tunica albuginea of
erectile bodies
Deep arteries
Corpus spongiosum
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The Male Duct System
• Ducts carry sperm from testes to body exterior
– Epididymis
– Ductus deferens
– Ejaculatory duct
– Urethra
Epididymis
• Pseudostratified epi cells with microvilli absorb
testicular fluid and pass nutrients to stored sperm
• Nonmotile sperm enter, become motile over ~20
days
– can be stored several months
• During ejaculation epididymis contracts, not
testes
Figure 27.3a Structure of the testis.
Spermatic cord
Blood vessels
and nerves
Ductus (vas)
deferens
Head of epididymis
Testis
Efferent ductule
Seminiferous
tubule
Rete testis
Lobule
Septum
Tunica albuginea
Straight tubule
Body of epididymis
Duct of epididymis
Tail of epididymis
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Tunica vaginalis
Cavity of
tunica vaginalis
Vas Deferens
• Ductus deferens (vas deferens)
• Passes through inguinal canal to pelvic cavity
• Expands to form ampulla
– joins duct of seminal vesicle to form ejaculatory duct
• Smooth muscle in walls propels sperm from
epididymis to urethra
Figure 27.1 Reproductive organs of the male, sagittal view.
Ureter
Peritoneum
Seminal gland
(vesicle)
Ampulla of
ductus deferens
Ejaculatory duct
Rectum
Prostate
Bulbo-urethral gland
Anus
Bulb of penis
Ductus (vas) deferens
© 2013 Pearson Education, Inc.
Epididymis
Testis
Scrotum
Urinary bladder
Prostatic
urethra
Pubis
Intermediate
part of the
urethra
Urogenital
diaphragm
Corpus
cavernosum
Corpus
spongiosum
Spongy
urethra
Glans penis
Prepuce
(foreskin)
External
urethral orifice
Seminal Glands
• On posterior bladder surface; smooth muscle
contracts during ejaculation
• Produces viscous alkaline seminal fluid
– Fructose, citric acid, coagulating enzyme (vesiculase),
and prostaglandins
– 70% volume of semen
• Duct of seminal gland joins ductus deferens to
form ejaculatory duct
The Prostate
• Encircles urethra inferior to bladder
– smooth muscle contracts during ejaculation
• Secretes milky, slightly acid fluid
– Contains citrate, enzymes, and prostate-specific
antigen (PSA)
– Role in sperm activation
• Enters prostatic urethra during ejaculation
• Constitutes 1/3 of semen volume
Urethra
• Conveys both urine and semen (at different
times)
• Has three regions
– Prostatic urethra – surrounded by prostate
– Intermediate part of the urethra (membranous
urethra) – in urogenital diaphragm
– Spongy urethra – runs through penis; opens at
external urethral orifice
Figure 27.1 Reproductive organs of the male, sagittal view.
Ureter
Peritoneum
Seminal gland
(vesicle)
Ampulla of
ductus deferens
Ejaculatory duct
Rectum
Prostate
Bulbo-urethral gland
Anus
Bulb of penis
Ductus (vas) deferens
© 2013 Pearson Education, Inc.
Epididymis
Testis
Scrotum
Urinary bladder
Prostatic
urethra
Pubis
Intermediate
part of the
urethra
Urogenital
diaphragm
Corpus
cavernosum
Corpus
spongiosum
Spongy
urethra
Glans penis
Prepuce
(foreskin)
External
urethral orifice
Bulbo-Urethral Glands
(Cowper's Glands)
• Pea-sized glands inferior to prostate
• Produce thick, clear mucus during sexual
arousal
– Lubricate glans penis
– Neutralize traces of acidic urine in urethra
Semen
• Milky-white mixture of sperm and accessory
gland secretions
• 2–5 ml semen ejaculated, contains 20–150
million sperm/ml
– Contains fructose for ATP production; protects and
activates sperm; facilitates sperm movement
– Alkaline to neutralize acidity of male urethra and
female vagina
– enhanced motility
Semen Function
• Prostaglandins decrease viscosity of mucus in
cervix and stimulate reverse peristalsis in uterus
• Hormone relaxin enhance sperm motility
• Suppresses female immune response
• Clotting factors coagulate semen to prevent
draining out
– liquefied by fibrinolysin for sperm motility
Meiosis
• Gamete formation involves meiosis
• Differs from mitosis
– Two consecutive cell divisions (meiosis I and II);
only one round of DNA replication
– Produces four daughter cells
• Functions of meiosis
– Number of chromosomes halved (from 2n to n)
– Introduces genetic diversity
Figure 27.6 Comparison of mitosis and meiosis in a mother cell with a diploid number (2n) of 4.
Mother cell
(before chromosome replication)
Chromosome
replication
Chromosome
replication
2n = 4
MITOSIS
MEIOSIS
Prophase
Replicated
chromosome
Prophase I
Tetrad formed by
synapsis of
replicated homologous
chromosomes
Metaphase
Chromosomes
align at the
metaphase plate
Metaphase I
Tetrads align randomly
at the metaphase plate
Sister chromatids separate
during anaphase
Homologous chromosomes
separate but sister chromatids
remain together during anaphase I
Daughter
cells of
mitosis
2n
Daughter cells
of Meiosis I
2n
Meiosis II
n
MITOSIS
Number of
divisions
Synapsis of
homologous
chromosomes
Daughter cell
number and
genetic
composition
Roles
in the body
One, consisting of prophase, metaphase,
anaphase, and telophase.
Does not occur.
No further chromosomal
replication; sister chromatids
separate during anaphase II
n
n
Daughter cells of meiosis II
(usually gametes)
MEIOSIS
Two, each consisting of prophase, metaphase, anaphase, and telophase.
DNA replication does not occur between the two nuclear divisions.
Occurs during prophase I; tetrads form, allowing crossovers.
Two. Each diploid (2n) cell is identical to
the mother cell.
Four. Each haploid (n) cell contains half as many chromosomes as the
mother cell and is genetically different from the mother cell.
For development of multicellular adult from
zygote. Produces cells for growth and tissue
repair as multicellular adult develops. Ensures
genetic makeup of all body cells is constant.
Produces cells for reproduction (gametes). Introduces genetic variability
in the gametes and reduces chromosomal number by half so that when
fertilization occurs, the normal diploid chromosomal number is restored
(in humans, 2n = 46).
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n
Spermatogenesis
• Sperm (spermatozoa) production in seminiferous tubules
– begins at puberty
• Most body cells have 46 chromosomes
– diploid chromosomal number (2n)
– Two sets (23 pairs) of chromosomes
– One maternal, one paternal – homologous chromosomes
• Gametes have 23 chromosomes
– haploid chromosomal number (n)
– Only one member of homologous pair
Spermatogenesis
• Spermatogenic cells give rise to sperm
• Mitosis of spermatogonia (stem cell) forms two
spermatocytes
• Meiosis
– Spermatocytes to secondary spermatocytes to spermatids
• Spermiogenesis (cellular differentiation/specialization)
– Spermatids become sperm
Figure 27.8b Spermatogenesis.
Basal lamina
Meiosis (early
spermatogenesis)
Spermiogenesis (late
spermatogenesis)
Spermatogenesis
Spermatogonium 2n
(stem cell)
Mitosis
Growth
Enters
meiosis I and
moves to
adluminal
compartment
Meiosis I
completed
Type A daughter cell
remains at basal lamina
as a precursor cell
2n
2n
Type B daughter cell
Primary
spermatocyte
2n
Secondary
spermatocytes
n
n
Meiosis ll
n
n
n
n
n
n
n
n
Early
spermatids
n
n
n
Late spermatids
n
Spermatozoa
Events of spermatogenesis, showing the relative
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Inc.
of various spermatogenic cells
Figure 27.9 Spermiogenesis: transformation of a spermatid into a functional sperm.
Slide 1
Approximately 24 days
Golgi apparatus
Acrosomal
vesicle
Mitochondria
Acrosome
Nucleus
1
2
Spermatid
nucleus
Centrioles
3
Microtubules
Flagellum
Midpiece Head
Excess
cytoplasm
4
Tail
5
6
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7
Sustentocytes
• Large supporting cells (Sertoli cells)
• Extend through wall of tubule and surround
developing cells
–
–
–
–
–
Provide nutrients and signals to dividing cells
Move cells along to lumen
Secrete testicular fluid into lumen for sperm transport
Phagocytize faulty germ cells and excess cytoplasm
Produce chemical mediators to regulate
spermatogenesis
Spermatogenesis
• Spermatogenesis occurs within and around
the cytoplasm of sustentocyte cells
• Tight junctions divide tubule into two
compartments
– Basal compartment—spermatogonia and primary
spermatocytes
– Adluminal compartment—meiotically active cells
and tubule lumen
Figure 27.8c Spermatogenesis.
Tight junction between sustentocytes
Spermatogonium
(stem cell)
Basal lamina
Cytoplasm of
adjacent
sustentocytes
Sustentocyte
cell nucleus
Basal
compartment
Type A daughter cell
remains at basal lamina
as a precursor cell
Type B daughter cell
Primary
spermatocyte
Secondary
spermatocytes
Late spermatids
Cytoplasmic bridge
Spermatozoa
Lumen
of seminiferous
tubule
Adluminal
compartment
Early
spermatids
A portion of the seminiferous tublule wall, showing the
spermatogenic cells surrounded by sustentocytes (colored gold)
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Importance of Tight Junctions
• Tight junctions form blood testis barrier
– Prevents sperm antigens from escaping into blood
which could activation of immune system
• Important - sperm not formed until puberty,
absent during immune system development,
would not be recognized as "self"
Hormonal Regulation
• Sequence of hormonal regulatory events
involving hypothalamus, anterior pituitary gland,
and testes
• Hypothalamic-pituitary-gonadal (HPG) axis
– Regulates production of gametes and sex hormones
through 3 interacting sets of hormones
– GnRH indirectly stimulates testes via FSH & LH
– FSH & LH directly stimulate testes
– Testosterone & inhibin – negative feedback on
hypothalamus and anterior pituitary
Sequence of Regulation
• Hypothalamus releases gonadotropin-releasing
hormone (GnRH)
– anterior pituitary to secrete FSH and LH
• FSH causes sustentocytes to release androgenbinding protein
– keeps high concentration of testosterone near
spermatogenic cells
• LH activates interstitial endocrine cells to release
testosterone
Figure 27.10 Hormonal regulation of testicular function, the hypothalamic-pituitary-gonadal (HPG) axis.
1
GnRH
Anterior
pituitary
Via portal
blood
7
6
Inhibin
FSH
3
2
LH
4
Interstitial
endocrine
cells
Testosterone
Sustentocyte 5
Spermatogenic
cells
Seminiferous
tubule
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Stimulates
Inhibits
Somatic and
psychological
effects at other
body sites;
maintenance
of secondary sex
characteristics
Slide 1
Feedback Regulation
• Rising testosterone levels
– inhibit GnRH and on pituitary to inhibit FSH/LH release
• Inhibin (released when sperm count high) –
inhibits GnRH and FSH release
• Three years to achieve balance
– testosterone and sperm production fairly stable
throughout life
Adult
Fertilization Birth
100
Puberty
50
0
3
6
Months
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9
1
10
Age
20
Years
60
Sperm production (% of maximal)
Plasma testosterone level
Figure 27.11 Plasma testosterone and sperm production levels versus age in male humans.
Female Reproductive System
• Ovaries - female gonads
– Produce female gametes (ova)
– Secrete female sex hormones, estrogen (estradiol,
estrone, estriol) and progesterone
• Accessory ducts include
– Uterine tubes
– Uterus
– Vagina
Ovaries
• Held in place by several ligaments
• Ovarian ligament
– anchors ovary medially to uterus
• Suspensory ligament
– anchors ovary laterally to pelvic wall
• Mesovarium
– suspends ovary
• Broad ligaments
Broad Ligament
• The collection of suspensory, mesosalpinx,
mesovarium and mesometrium ligaments that
create a peritoneal fold
– Supports uterine tubes, uterus, and vagina
Figure 27.14 Internal reproductive organs of a female, posterior view.
Suspensory
ligament of ovary
Ovarian
blood
vessels
Broad ligament
• Mesosalpinx
• Mesovarium
• Mesometrium
Uterine (fallopian) tube
Ovarian
ligament
Body of uterus
Ureter
Uterine blood vessels
Isthmus
Uterosacral ligament
Cardinal (lateral cervical)
ligament
Lateral fornix
Cervix
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Fundus
Lumen (cavity)
of uterus
of uterus
Ovary
Uterine tube
• Ampulla
• Isthmus
• Infundibulum
• Fimbriae
Round ligament of uterus
Wall of uterus
• Endometrium
• Myometrium
• Perimetrium
• Internal os
• Cervical canal
• External os
Vagina
Ovaries
• Surrounded by fibrous tunica albuginea
• Germinal epithelium - outer layer
• Two poorly defined regions
– Outer cortex – houses forming gametes
– Inner medulla - large blood vessels and nerves
Ovarian Cortex
• Ovarian follicles
– Immature egg (oocyte)
• Follicle cells surrounding oocyte
– one cell layer thick
• Granulosa cells
– more than one layer present
Follicle development
• Several stages of development
• Primordial follicle
– single layer of follicle cells + oocyte
• More mature follicles
– several layers of granulosa cells
Follicle development
• Vesicular (antral or tertiary) follicle
– fully mature follicle
• Fluid-filled antrum forms and follicle bulges
from ovary surface
• Ovulation
– Ejection of oocyte from ripening follicle
Figure 27.13 Photomicrograph of a mammalian ovary showing follicles in different developmental phases.
Germinal
epithelium
Tunica
albuginea
Cortex
Medulla
Primary
follicles
Secondary
follicle
Antrum of a vesicular
(antral) follicle
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Female Duct System
• Ducts have no contact with ovary
– Oocyte cast into peritoneal cavity; some lost there
• Uterine (fallopian) tubes or oviducts
• Uterus
• Vagina
Uterine Tubes
• Receive ovulated oocyte; usual site of fertilization
• Isthmus
– constricted region where tube joins uterus
• Ampulla
– Distal expansion with infundibulum near ovary
• Infundibulum
– funnel shaped structure bearing ciliated fimbriae of
create currents to move oocyte into uterine tube
Uterine Tubes
• Oocyte carried along by peristalsis and ciliary
action
• Nonciliated cells have dense microvilli to
nourish oocyte and sperm
• Mesosalpinx supports uterine tubes
Figure 27.14 Internal reproductive organs of a female, posterior view.
Suspensory
ligament of ovary
Ovarian
blood
vessels
Broad ligament
• Mesosalpinx
• Mesovarium
• Mesometrium
Uterine (fallopian) tube
Ovarian
ligament
Body of uterus
Ureter
Uterine blood vessels
Isthmus
Uterosacral ligament
Cardinal (lateral cervical)
ligament
Lateral fornix
Cervix
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Fundus
Lumen (cavity)
of uterus
of uterus
Ovary
Uterine tube
• Ampulla
• Isthmus
• Infundibulum
• Fimbriae
Round ligament of uterus
Wall of uterus
• Endometrium
• Myometrium
• Perimetrium
• Internal os
• Cervical canal
• External os
Vagina
Uterus
• Hollow, thick-walled, muscular organ
• Function: Receive, retain, nourish fertilized ovum
• Composed of:
–
–
–
–
Body - major portion
Fundus - rounded superior region
Isthmus - narrowed inferior region
Cervix - narrow neck, or outlet; projects into vagina
Ligament Support of Uterus
• Mesometrium
– lateral support
• Cardinal (lateral cervical ) ligaments
– extends from cervix to lateral walls of pelvis
• Uterosacral ligaments
– secure uterus to sacrum
• Round ligaments
– bind to anterior wall
Layers of the Uterus
• Perimetrium - serous layer (visceral
peritoneum)
• Myometrium - interlacing layers of smooth
muscle
• Endometrium - mucosal lining
Figure 27.14 Internal reproductive organs of a female, posterior view.
Suspensory
ligament of ovary
Ovarian
blood
vessels
Broad ligament
• Mesosalpinx
• Mesovarium
• Mesometrium
Uterine (fallopian) tube
Ovarian
ligament
Body of uterus
Ureter
Uterine blood vessels
Isthmus
Uterosacral ligament
Cardinal (lateral cervical)
ligament
Lateral fornix
Cervix
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Fundus
Lumen (cavity)
of uterus
of uterus
Ovary
Uterine tube
• Ampulla
• Isthmus
• Infundibulum
• Fimbriae
Round ligament of uterus
Wall of uterus
• Endometrium
• Myometrium
• Perimetrium
• Internal os
• Cervical canal
• External os
Vagina
Endometrium Layers
• Stratum functionalis (functional layer)
– Changes in response to ovarian hormone cycles
– Shed during menstruation
• Stratum basalis (basal layer)
– Forms new functionalis after menstruation
– Unresponsive to ovarian hormones
Figure 27.15a The endometrium and its blood supply.
Lumen of uterus
Epithelium
Uterine glands
Stratum
functionalis
of the
endometrium
Lamina propria of
connective tissue
Stratum
basalis
of the
endometrium
Portion
of the
myometrium
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Smooth muscle
fibers
Figure 27.15b The endometrium and its blood supply.
Lumen of uterus
Epithelium
Capillaries
Uterine glands
Venous sinusoids
Lamina propria of
connective tissue
Spiral (coiled)
artery
Straight artery
Endometrial vein
Radial artery
Smooth muscle
fibers
Arcuate artery
Uterine artery
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Cervix
• Cervix is a narrow neck that projects into
vagina
• Cervical canal communicates with
– Vagina via external os
– Uterine body via internal os
• Cervical glands secrete mucus that blocks
sperm entry except during midcycle
The Vagina
• Cervix opens into vagina
• Thin-walled tube serves as birth canal
Vagina
• Layers of wall
– Fibroelastic adventitia
– Smooth muscle muscularis
– Stratified squamous mucosa with rugae
• Vaginal fornix - upper end of vagina surrounding
cervix
• Mucosa near vaginal orifice forms incomplete
partition called hymen
Figure 27.14 Internal reproductive organs of a female, posterior view.
Suspensory
ligament of ovary
Ovarian
blood
vessels
Broad ligament
• Mesosalpinx
• Mesovarium
• Mesometrium
Uterine (fallopian) tube
Ovarian
ligament
Body of uterus
Ureter
Uterine blood vessels
Isthmus
Uterosacral ligament
Cardinal (lateral cervical)
ligament
Lateral fornix
Cervix
© 2013 Pearson Education, Inc.
Fundus
Lumen (cavity)
of uterus
of uterus
Ovary
Uterine tube
• Ampulla
• Isthmus
• Infundibulum
• Fimbriae
Round ligament of uterus
Wall of uterus
• Endometrium
• Myometrium
• Perimetrium
• Internal os
• Cervical canal
• External os
Vagina
The Female Reproductive Cycle
• Females total supply of eggs determined at
birth
• Preliminary evidence suggests stem cells may
produce more oocytes
Oogenesis
• Production of female gametes
– Takes years to complete
– Begins in fetal period
• Oogonia (2n ovarian stem cells) multiply by
mitosis and store nutrients
• Primary oocytes develop in primordial follicles
• Primary oocytes begin meiosis; stall in prophase I
Oogenesis – Meiosis I
• Each month after puberty, a few primary
oocytes activated
• One "selected" each month to resume
meiosis I
• Result is two haploid cells of different sizes
– Secondary oocyte – large cell with ~ all cytoplasm
and organelles of original cell
– First polar body – small cell
Oogenesis – Meiosis II
• Secondary oocyte arrests in metaphase II
– ovulated ovum
• If not penetrated by sperm - deteriorates
• If penetrated by sperm second oocyte completes
meiosis II, yielding
– Ovum (functional gamete)
– Second polar body
Figure 27.19 Events of oogenesis.
Follicle development
in ovary
Meiotic events
Before birth
Oogonium (stem cell)
2n
Follicle cells
Oocyte
Mitosis
Infancy and
childhood
(ovary functionally
inactive)
2n
Primary oocyte
Primordial follicle
2n
Primary oocyte
(arrested in prophase I;
present at birth)
Primordial follicle
Each month from
puberty to menopause
Primary follicle
Primary oocyte (still
arrested in prophase I)
2n
Secondary follicle
Spindle
Vesicular (antral)
follicle
Meiosis I (completed by
one primary oocyte each
month in response to
LH surge)
Secondary oocyte
(arrested in metaphase II)
n
First polar body
Ovulation
Meiosis II of polar body
(may or may not occur)
Polar bodies
(all polar bodies
degenerate)
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n
Sperm
n
n
n
Second
Ovum
polar body
Ovulated secondary
oocyte
Meiosis II
completed
(only if sperm
penetrates
oocyte)
In absence of fertilization,
ruptured follicle becomes
a corpus luteum and
ultimately degenerates.
Degenerating
corpus luteum
Oogenesis vs Spermatogenesis
• Spermatogenesis produce 4 viable sperm
– error rate of 3-4%
• Oogenesis produce 1 viable gamete + 3 polar bodies
– error rate of 20%
• Unequal divisions ensure oocyte has ample nutrients
for 6-7 day journey to uterus
• Polar bodies degenerate and die
Ovarian Cycle
• Monthly series of events associated with
maturation of egg
• Two consecutive phases (in 28-day cycle)
– Follicular phase - period of follicle growth (days 1–14)
– Luteal phase - period of corpus luteum activity
(days 14–28)
• Ovulation occurs midcycle
Ovarian Cycle
• Only 10 – 15% women have 28-day cycle
• Time of follicular phase varies
• Luteal phase constant – always 14 days from
ovulation to end of cycle
Follicular Phase
• Primordial follicle becomes primary follicle
– Squamous-like cells become cuboidal; oocyte
enlarges
• Primary follicle becomes secondary follicle
– Stratified epithelium (granulosa cells) forms
around oocyte
• Granulosa cells and oocyte guide one
another's development via gap junctions
Figure 27.20 Schematic and microscopic views of the ovarian cycle: development and fate of ovarian follicles.
Theca folliculi
2
3a
3b
Primary
oocyte
Zona pellucida
Antrum
Secondary
4
oocyte
7
5
6
6
Corona
radiata
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Secondary
oocyte
1 Primordial
follicles
Slide 2
Figure 27.20 Schematic and microscopic views of the ovarian cycle: development and fate of ovarian follicles.
Theca folliculi
2
3a
3b
Primary
oocyte
Zona pellucida
Antrum
Secondary
4
oocyte
7
5
6
6
Corona
radiata
© 2013 Pearson Education, Inc.
Secondary
oocyte
2 Primary
follicle
Slide 3
Figure 27.20 Schematic and microscopic views of the ovarian cycle: development and fate of ovarian follicles.
Theca folliculi
2
3a
3b
Primary
oocyte
Zona pellucida
Antrum
Secondary
4
oocyte
7
5
6
6
Corona
radiata
© 2013 Pearson Education, Inc.
Secondary
oocyte
3a Secondary
follicle
Slide 4
Follicular Phase
• Secondary follicle becomes late secondary
follicle
– Connective tissue (theca folliculi) and granulosa
cells cooperate to produce estrogens
• Inner thecal cells produce androgens in
response to LH
– Zona pellucida forms around oocyte
– Fluid accumulates between granulosa cells
Follicular Phase
• Late secondary follicle becomes vesicular
follicle
– Antrum forms; expands to isolate oocyte
• Vesicular follicle bulges from external surface
of ovary
– Primary oocyte completes meiosis I producing
secondary oocyte and first polar body
Figure 27.20 Schematic and microscopic views of the ovarian cycle: development and fate of ovarian
Theca folliculi
3a
follicles. Slide 5
Theca
folliculi
3b
2
Primary
oocyte
Zona pellucida
Antrum
Secondary
4 oocyte
7
5
6
6
© 2013 Pearson Education, Inc.
Corona
radiata
Secondary
oocyte
Forming
3b Late
secondary antrum
follicle
Figure 27.20 Schematic and microscopic views of the ovarian cycle: development and fate of ovarian
Theca folliculi
3a
3b
Zona
pellucida
Primary
oocyte
Zona pellucida
Antrum
Secondary
4 oocyte
2
7
5
6
6
© 2013 Pearson Education, Inc.
Corona
radiata
Secondary
oocyte
follicles. Slide 6
Antrum
Antrum
4 Mature vesicular
follicle carries out
meiosis I; ready to
be ovulated
4
Ovulation
• Ovary wall ruptures, expels secondary oocyte
with its corona radiata into te peritoneal
cavity
• 1–2% of ovulations release more than one
secondary oocyte
– if fertilized, results in fraternal twins
– Identical twins result from fertilization of one
oocyte, then separation of daughter cells
Figure 27.20 Schematic and microscopic views of the ovarian cycle: development and fate of ovarian
Theca folliculi
3a
follicles. Slide 7
3b
2
Primary
oocyte
Zona pellucida
Antrum
Secondary
4 oocyte
7
5
6
6
© 2013 Pearson Education, Inc.
Corona
radiata
Secondary
oocyte
5 Follicle ruptures;
secondary oocyte
ovulated
Luteal Phase of the Ovarian Cycle
• Ruptured follicle collapses; antrum fills with
clotted blood
– corpus hemorrhagicum
• Granulosa cells and internal thecal cells form
corpus luteum
• Corpus luteum secretes progesterone and some
estrogen
Luteal Phase of the Ovarian Cycle
• If no pregnancy:
– corpus luteum degenerates into corpus albicans
(scar) in 10 days
• If pregnancy occurs:
– corpus luteum produces hormones that sustain
pregnancy until placenta takes over at about
3 months
Figure 27.20 Schematic and microscopic views of the ovarian cycle: development and fate of ovarian
Theca folliculi
3a
follicles. Slide 8
3b
2
Primary
oocyte
Zona pellucida
Antrum
Secondary
4 oocyte
7
5
6
6
© 2013 Pearson Education, Inc.
Corona
radiata
Secondary
oocyte
6 Corpus luteum
(forms from
ruptured follicle)
Figure 27.20 Schematic and microscopic views of the ovarian cycle: development and fate of ovarian follicles.
1 Primordial 2 Primary
follicle
follicles
3 Secondary
Theca folliculi
3b follicle
3a
3b Late secondary
2
Primary follicle
7
oocyte
Zona pellucida
Antrum
Secondary
4 oocyte
Secondar
5
6
y
oocyte
6
Corona
Zona
radiata
pellucida
Theca
folliculi
Forming
antrum
Antrum
6 Corpus luteum
(forms from ruptured
© 2013 Pearson Education, Inc.
follicle)
5 Follicle ruptures;
secondary oocyte
ovulated
4 Mature vesicular follicle
carries out meiosis I; ready
to be ovulated
Slide 9
Establishing the Ovarian Cycle
• During childhood:
– ovaries grow and secrete small amounts of estrogens
that inhibit hypothalamic release of GnRH
• As puberty nears:
– GnRH released; FSH and LH released by pituitary, and
act on ovaries
• These events continue until an adult cyclic
pattern achieved and menarche occurs
Hormonal Regulation
• Hormone interaction produces cyclic events in
ovaries
– Gonadotropin-releasing hormone (GnRH)
– Pituitary gonadotropins
– Ovarian estrogen
– Ovarian progesterone
• Onset of puberty linked to amount of adipose
tissue via hormone leptin
Establishing the Ovarian Cycle
• During childhood, until puberty
– Ovaries secrete small amounts of estrogens
– Estrogen inhibits release of GnRH
• If leptin levels adequate hypothalamus less
sensitive to estrogen as puberty nears
– releases GnRH in rhythmic pulse-like manner
– FSH and LH release
– ovarian hormone release
Onset of Puberty
• Gonadotropin levels increase for about four
years
– no ovulation; no pregnancy
• Adult cyclic pattern achieved and menarche
occurs
– First menstrual period
• Three years before cycle regular and all ovulatory
Hormonal Interactions During a 28-Day
Ovarian Cycle
1. GnRH release of FSH and LH
2. FSH and LH growth of several follicles, and
hormone release
3. plasma estrogen levels inhibit release of FSH
and LH
estrogen levels enhance further estrogen output
Inhibin from granulosa cells also inhibits FSH
release
Hormonal Interactions During a 28-Day
Ovarian Cycle
4. When estrogen levels high  brief positive feedback
on brain and anterior pituitary
5. Stored LH, and some FSH, suddenly released by
anterior pituitary at midcycle  surge triggers ovulation
 primary oocyte to complete meiosis I  secondary
oocyte
Secondary oocyte  meiosis II
Hormonal Interactions During a 28-Day
Ovarian Cycle
• LH effects at midcycle
– Increases local vascular permeability
– Triggers inflammatory response  weakens
ovarian wall
–  Blood flow stops through protruding follicle
wall  wall thins, bulges, ruptures
– Oocyte with corona radiata exits (ovulation)
Hormonal Interactions During a 28-Day
Ovarian Cycle
• After ovulation
– Estrogen levels decline
– LH transforms ruptured follicle  corpus luteum
– LH stimulates corpus luteum  progesterone and
some estrogen almost immediately
• Progesterone helps maintain stratum functionalis
• Maintains pregnancy, if occurs
Hormonal Interactions During a 28-Day
Ovarian Cycle
6. Negative feedback (from rising plasma
progesterone and estrogen levels) inhibits LH
and FSH release
– Inhibin, from corpus luteum and granulosa cells,
enhances effect
– Declining LH ends luteal activity, inhibits follicle
development
Hormonal Interactions During a 28-Day
Ovarian Cycle
• If no fertilization
– Corpus luteum degenerates when LH levels fall 
sharp decrease in estrogen and progesterone 
ends blockage of FSH and LH secretion
–  Cycle starts anew
A new cycle
• More happening than the 28-day cycle
• Increasing FSH at beginning of each cycle allows
for several vesicular follicles to continue to
mature
• Midcycle LH surge allows more than one vesicular
follicle to mature and undergo ovulation
– activation can be as early as 1 year, not 14 days
Figure 27.21 Regulation of the ovarian cycle.
Hypothalamus
Slide 1
Hypothalamus
GnRH
GnRH
Travels via
portal blood
1
1
FSH
2
3 Slightly
elevated
estrogen and
rising inhibin
levels inhibit
FSH
secretion.
Anterior pituitary
LH
2
Thecal cells
2
Androgens
4 Positive
feedback exerted
by large in
estrogen output
by maturing
follicle.
4
6
4
Progesterone
Estrogens
Inhibin
LH surge
Ruptured
5
follicle
6
5
Granulosa
cells
2
Mature vesicular
Inhibin
Convert androgens
follicle
Ovulated
Corpus luteum
to estrogens
secondary
2
oocyte
Estrogens
Late follicular and
Early and
luteal phases
midfollicular phases
Stimulates
© 2013 Pearson Education, Inc.
Inhibits
Plasma hormone level
Figure 27.22a Correlation of anterior pituitary and ovarian hormones with structural changes of the ovary and uterus.
LH
FSH
Fluctuation of gonadotropin levels: Fluctuating levels of pituitary
gonadotropins (follicle-stimulating hormone and luteinizing hormone)
in the blood regulate the events of the ovarian cycle.
© 2013 Pearson Education, Inc.
Figure 27.22b Correlation of anterior pituitary and ovarian hormones with structural changes of the ovary and uterus.
Primary Secondary Vesicular Ovulation
follicle follicle
follicle
Follicular
phase
Ovulation
(Day 14)
Corpus
luteum
Degenerating
corpus luteum
Luteal
phase
Ovarian cycle: Structural changes in the ovarian follicles during the
ovarian cycle are correlated with (d) changes in the endometrium of the
uterus during the uterine cycle.
© 2013 Pearson Education, Inc.
The Menstrual Cycle
• Cyclic changes in endometrium in response to
fluctuating ovarian hormone levels
• Three phases
– Days 1–5 - menstrual phase
– Days 6–14 - proliferative (preovulatory) phase
– Days 15–28 - secretory (postovulatory) phase
(constant 14-day length)
The Uterine Cycle
• Menstrual phase (Days 1 - 5)
– Ovarian hormones at lowest levels
– Gonadotropins beginning to rise
– Stratum functionalis shed; menstrual flow (blood
and tissue) 3 - 5 days
– By day 5 growing ovarian follicles produce more
estrogen
The Uterine Cycle
• Proliferative phase (Days 6 - 14)
– Rising estrogen levels prompt generation of new
stratum functionalis layer; increased synthesis of
progesterone receptors in endometrium; glands
enlarge and spiral arteries increase in number
– Normally thick, sticky cervical mucus thins in response
to rising estrogen (allows sperm passage)
– Ovulation occurs at end of proliferative phase
The Uterine Cycle
• Secretory phase (Days 15 – 28)
– Most constant timewise
– Endometrium prepares for embryo
– Rising progesterone levels prompt
• Functional layer forms secretory mucosa
• Endometrial glands secrete nutrients
• Formation of cervical mucus plug
Plasma hormone level
Figure 27.22c Correlation of anterior pituitary and ovarian hormones with structural changes of the ovary and uterus.
Estrogens
Progesterone
Fluctuation of ovarian hormone levels: Fluctuating levels of ovarian
hormones (estrogens and progesterone) cause the endometrial changes
of the uterine cycle. The high estrogen levels are also responsible for the
LH/FSH surge in (a).
© 2013 Pearson Education, Inc.
Figure 27.22d Correlation of anterior pituitary and ovarian hormones with structural changes of the ovary and uterus.
Endometrial
glands
Blood vessels
Menstrual
flow
Functional
layer
Basal layer
Days 1
5
Menstrual
phase
10
Proliferative
phase
15
25
20
Secretory
phase
28
The three phases of the uterine cycle:
• Menstrual: The functional layer of the endometrium is shed.
• Proliferative: The functional layer of the endometrium is rebuilt.
• Secretory: Begins immediately after ovulation. Enrichment of the blood
supply and glandular secretion of nutrients prepare the endometrium to
receive an embryo.
Both the menstrual and proliferative phases occur before ovulation, and
together they correspond to the follicular phase of the ovarian cycle. The
secretory phase corresponds in time to the luteal phase of the ovarian cycle.
© 2013 Pearson Education, Inc.
No Fertilization
• If fertilization does not occur
– Corpus luteum degenerates toward end of
secretory phase
– Progesterone levels fall
– Spiral arteries kink and spasm
– Endometrial cells begin to die; glands regress
– Spiral arteries constrict again, then relax and open
wide
– Rush of blood fragments weakened capillary beds
and functional layer sloughs
Estrogen
• Promote oogenesis and follicle growth in
ovary
• Exert anabolic effects on female reproductive
tract
• Support rapid but short-lived growth spurt at
puberty
Other Effects of Estrogen
• Secondary sex characteristics
– Growth of breasts
– Increased deposit of subcutaneous fat (hips and
breasts)
– Widening and lightening of pelvis
• Metabolic effects
– Maintain low total blood cholesterol and high HDL
levels
– Facilitate calcium uptake
Progesterone
• Progesterone works with estrogen to establish
and regulate uterine cycle
• Promotes changes in cervical mucus
• Effects of placental progesterone during
pregnancy
– Inhibits uterine motility
– Helps prepare breasts for lactation
Determination of Genetic Sex
• Of 46 chromosomes in fertilized egg, two (one
pair) are sex chromosomes
• Two sex chromosomes – X chromosome and Y
chromosome
• Females are XX
– each ovum always has an X chromosome
• Males are XY
– 50% of sperm contain X, 50% contain Y
Determination of Genetic Sex
• X egg + X sperm  XX (female offspring)
• X egg + Y sperm  XY (male offspring)
• The SRY gene on Y chromosome initiates
testes development and maleness
• Automatic program to develop female unless
SRY gene is activated
Lab Exercise for today
• Lab Exercise 42
• You can start Exercise 43 if you wish