Tonic and Preovulatory Surge of GnRH Preovulatory GnRH Surge Tonic GnRH Release GnRH pg ml GnRH pg ml Hours Hours Hypothalamus GnRH Anterior Pituitary CL Follicle Ovary LH FSH ID: 659366
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Slide1
Animal Science 434
The Follicular Phase of the Estrous CycleSlide2
Tonic and Preovulatory Surge of GnRH
Preovulatory
GnRH Surge
Tonic
GnRH Release
GnRH (
pg
/ml)
GnRH (pg/ml)
Hours
HoursSlide3
Hypothalamus
GnRH
Anterior
Pituitary
CL
Follicle
Ovary
LH, FSH
LH
LH, FSH
Inhibin (-)
Estradiol
Progesterone
Estradiol
(-)
(-)Slide4
Tonic and Preovulatory Surge of GnRH
Preovulatory
GnRH Surge
Tonic
GnRH Release
GnRH (
pg
/ml)
GnRH (pg/ml)
Hours
HoursSlide5
The
Follicular
PhaseSlide6
Hypothalamus
GnRH
Anterior
Pituitary
Follicle
Ovary
LH, FSH
LH, FSH
Inhibin (-)
Estradiol
Estradiol
(-)
LH
Progesterone
(-)
CL
Start of Follicular PhaseSlide7
Estradiol
(-)
Hypothalamus
GnRH
Anterior
Pituitary
Follicle
Ovary
LH, FSH
LH, FSH
Inhibin (-)
Estradiol
CL RegressionSlide8
Estradiol
(+)
Hypothalamus
GnRH
Anterior
Pituitary
Follicle
Ovary
LH, FSH
LH, FSH
Inhibin (-)
Estradiol
Ends in LH surge
and ovulationSlide9
The
Follicular
PhaseSlide10
Tertiary
Follicular
Progression
Primordial
Primary
SecondarySlide11
Growth and Atresia of Follicles
AtresiaSlide12
At birth 100,000
12 months 75,000
4-6 years 21,000
Aged cow 2,500
Follicles
undergo atresia at all stages of development.
Maximum
number of oocytes ovulated for a
cow
17
cycles/year x 8 year =
136 oocytes ovulated /
lifespan
Fate of follicles and oocytes
Superovulation or Ovum Pick-up (OPU) -
rescue
some follicles from atresia
100 Days
of Gestation 2.9 millionSlide13
Gonadotropin
Independent
Initial Follicular Growth
Small Antral
Follicle
50 - 60 days
FSH
RecruitmentSlide14
Follicular Waves in CattleSlide15
Ovulation
Follicular Size
Day
9
16
21
Ovulation
FSH Sensitive Pool
Recruitment
Selection
Dominance
AtresiaSlide16
Ovulation
Ovulation
Follicular Size
9
16
21
FSH Sensitive Pool
Recruitment
Selection
Dominance
Atresia
Progesterone
DaySlide17
Ovulation
Follicular Size
9
16
21
Recruitment
FSH estradiol (-)
Selection
FSH estradiol (-)
inhibin (-)
Dominance
FSH estradiol (-)
inhibin (-)
Atresia
estradiol
inhibin
Progesterone
FSH
DaySlide18
Ovulation
Follicular Size
9
16
21
Recruitment
Selection
Dominance
Atresia
Progesterone
DaySlide19
Ovulation
Follicular Size
9
16
21
Progesterone
DaySlide20
Ovulation
Follicular Size
9
16
21
Progesterone
DaySlide21
Ovulation
Follicular Size
9
16
21
Dominance
Recruitment
Selection
Ovulation
Progesterone
DaySlide22
Two Follicular WavesSlide23
10
Ovulation
21
Follicular Size
Recruitment
Selection
Dominance
Atresia
Ovulation
Progesterone
DaySlide24
Follicular Wave Emergence
Recruitment = Emergence
FSH always controls emergence
Increase in FSH precedes emergenceSlide25
Species Variation in Follicular Waves
Cattle - 2 or 3 / cycle
Sheep - 4 or 5 / cycle
Pigs - 1 / cycleHorses - 1 / cycleHuman - 1 / cycle
Cl-progesterone
Cl-progesterone, inhibin
If first
wave stops/fails,
then a second wave emerges!!!Slide26
Gonadotropin Action Within
the FollicleSlide27
Antral Follicle
Granulosa
Theca InternalSlide28
Theca
Interna
Granulosa
Blood
Receptor
LH
cAMP
Cholesterol
Testosterone
PKA
Receptor
FSH
Test.
cAMP
Estradiol
PKASlide29
Blood
Receptor
LH
cAMP
Cholesterol
Testosterone
PKA
Receptor
FSH
Test.
cAMP
Estradiol
PKA
cAMP
Receptor
LH
Selection
Dom.
Foll
.
Express LH Receptor
Theca
Interna
GranulosaSlide30
OvulationSlide31
Tunica
Albuginea
Germinal Epithelium
Theca Externa
Theca
Interna
Granulosa
Basement MembraneSlide32
protein synthesis
steroid synthesis
prostaglandin synthesis
plasminogen activator synthesis
Blocking of these events in the
follicle prevents ovulation.Slide33
Preovulatory
LH Surge
Ovulation
Cumulus
Expansion
Oocyte
Separates
From
Follicular
WallSlide34
Cumulus Expansion
Unexpanded
Expanded
Hyaluronic
Acid
and
Protein ProductionSlide35
Cumulus and Oocyte
SeparationSlide36
Protein synthesis changes
in and around Follicle
Plasminogen
Activator
Progesterone
Prostaglandin Synthesis
PGE and PGF
Preovulatory
LH Surge
Ovulation
Cumulus
Expansion
Oocyte
Separates
From
Follicular
WallSlide37
Preovulatory
LH Surge
Ovulation
Cumulus
Expansion
Oocyte
Separates
From
Follicular
Wall
Protein synthesis changes
in and around Follicle
Plasminogen
Activator
Progesterone
Prostaglandin Synthesis
PGE and PGF
Increased Blood
Flow to Ovary and
Follicle
Vascular Permeability
Plasminogen
Histamine, PGE
2
Foll
. pressure
EdemaSlide38
Preovulatory
LH Surge
Ovulation
Cumulus
Expansion
Oocyte
Separates
From
Follicular
Wall
Protein synthesis changes
in and around Follicle
Plasminogen
Activator
Progesterone
Prostaglandin Synthesis
PGE and PGF
Increased Blood
Flow to Ovary and
Follicle
Vascular Permeability
Plasminogen
Histamine, PGE
2
Foll
. pressure
Edema
Collagen. (inact.)
Follicular Wall Weakens
Plasmin
Collagenase (
act.)Slide39
Preovulatory
LH Surge
Ovulation
Cumulus
Expansion
Oocyte
Separates
From
Follicular
Wall
Contraction
Sm. Muscle
Collagen.
(
inact
.)
Follicular
Wall Weakens
Plasmin
Collagenase (
act.)
Protein synthesis changesin and around FolliclePlasminogenActivator
Progesterone
Prostaglandin Synthesis
PGE and PGF
Increased Blood
Flow to Ovary and Follicle
Vascular PermeabilityPlasminogen
Histamine, PGE
2
Foll
. pressure
EdemaSlide40
Types of OvulatorsSlide41
Spontaneous
OvulatorsSlide42
Induced
OvulatorsSlide43
Sensory Neurons
Nerve endings sensing copulation
Penis
Copulation
Induced
OvulatorsSlide44
GnRH
Blood LH
Time (
hr
)
LH
Spinal Chord
Anterior Pit.
Posterior Pit.
Hypothalamus
StimulationSlide45
Sensory Neurons
Nerve endings sensing copulation
Penis
Copulation
Induced
Ovulators
LHSlide46
Cats
Induced
Ovulators
Single copulation
Only works 50% of the timeMultiple copulations
Higher LH surge Slide47
Spontaneous Ovulators
Retain some neural control of ovulation
heifers can alter the timing of the LH surge by clitoral stimulation
human rape cases result in higher than expected pregnancy ratesSlide48
Oogenesis
Primordial Germ Cells
Oogonia
Primary Oocyte
Meiosis
Interphase
DNA
synthesis
Meiotic prophase
Move
to
germinal
ridge
Mitotic divisions
Prophase of
Meiosis
Leptotene
,
Zygotene
Pacytene
,
Diplotene
Dictyotene
Meiotic Arrest
Follicle CellsSlide49
Growth
zona
pellucida
formation
mRNA production
Protein synthesis
Cortical granule formation
nuclear
maturation
cytoplasmic maturation
Gonadotropin
Independent
Gonadotropin
Dependent
Remains
primary oocyte until LH surgeSlide50
Oogonia
in Egg Nest
Fetal Pig OvarySlide51
Primary Oocytes
OogoniaSlide52
Primary Oocytes in Primordial FolliclesSlide53
Primary Oocyte in Primary FollicleSlide54
Fetal Oocyte Development
Fertilization
Birth
Mitosis
Meiosis
Mouse
19 d
Sow
114 d
Cow
280 dSlide55
Ovulation of Tertiary FollicleSlide56
Formation of the Zona
Pellucida
Corona
Radiata
Zona
Pellucida
OocyteSlide57
Corona
Radiata
Zona
Pellucida
Oocyte
Gap JunctionsSlide58
OMI - Oocyte Maturation Inhibitor
MPF - Maturation promoting factor
GV - germinal vesicle
(nucleus)
During Oocyte Growth and Before the LH Surge
Gap Junctions Allow Cell to Cell Communication!
pre-MPF
MPF
GV
OMI
cAMP
cAMP
PKASlide59
The LH Surge
Gap Junctions are Destroyed!Slide60
GV
GVBD
Resumption
of Meiosis
pre-MPF
MPF
cAMP
PKA
The LH Surge
Gap Junctions are Destroyed!Slide61
LH Surge
Resumption
of Meiosis
First polar
body
emitted
,
arrest at metaphase II
Ovulation
Primary Oocyte
Secondary
Oocyte
Sperm Penetration
Zygote
(
pronucleate
egg)
4N
4N
2N
2N
N
N
(
most
species
)Slide62
LH Surge
Resumption
of Meiosis
First polar
body
emitted
,
arrest at metaphase II
Ovulation
Primary Oocyte
Secondary
Oocyte
Sperm Penetration
4N
4N
2N
2N
N
N
(
most
species
)
Ovulation
Dog,
Fox
Sperm
Pen.
Dog
,
Fox
Zygote
(
pronucleate
egg)