Ovarian Physiology

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Ovarian Physiology
R. Jeffrey Chang, M.D. Department of Reproductive
Medicine UCSD School of Medicine
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Ovarian Physiology

• Pelvic anatomy
• Formation of the ovary
• Folliculogenesis
• Ovulation
• Corpus luteum formation

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Female Pelvic Structures
Fallopian tube or oviduct
Uterus
Fimbria
Ovary
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Anatomy of Female Reproductive System
Fallopian tube or oviduct
Endometrium
Ovary
Fimbria
Myometrium
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Section of Human Ovary
Tertiary follicle
Ovarian blood vessels
Graafian follicle
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Ovarian Histology
Oocyte
Granulosa cells
Theca cells
medulla
Follicles
cortex
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Development of the Ovary
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Origin of Primordial Germ Cells
Endometrium
X
Primordial Germ Cells
Implantation site at end of 2nd week
2005 Lippincott Williams Wilkins
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Germ Cell Formation in Mammals
Blastocyst cell
Bone Morphogenetic Proteins (BMP-2, 4, 8b)
Primordial Germ Cells
Unspecialized Somatic cell
Concept PGCs differentiate from somatic lineage
by a BMP inductive mechanism.
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Migration of Primordial Germ Cells
Presomite embryo
7-somite embryo
PGCs
PGCs
PGCs
PGCs
4-week embryo
5-week embryo
PGCs
2005 Lippincott Williams Wilkins
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• Primordial Germ Cells
• Identified by
• Large size
• Lipid droplets
• Alkaline phosphatase
• Regulatory Factors
• Oct4 (transcription factor)
• c-kit (tyrosine kinase)
• Stem cell factor
• Laminin
• Fibronectin

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Growth factors are required for PGC migration and
proliferation. For example, mutations in kit
ligand or Kit receptor cause deficiencies in PGC
number which lead to decreased ovarian reserve
and infertility.
Kit L mutant
Wild type
PGCs stained for alkaline phosphatase
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Genital ridge composed of PGCs (6th week)
PGCs (XX or XY) failing to enter the gonad will
become oogonia and the ovary will not develop
Fetal gonads are bipotential until about the 6th
week
PGCs
Sex-determining Region on the Y
XY SRY Sertoli cells
XX
Oogonia (required for ovary formation)
Spermatogonia (not required for testes formation)
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Concept
Gonad differentiation (sex determination) is
controlled by the testis determining gene, SRY
(Sex-determining Region on the Y) which causes
differentiation of Sertoli Cells and testes.
Unlike the testes, without germ cells containing
XX an ovary will not develop.
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Germ Cell Count(human ovary) Oogonia
increase in fetal ovaries is markedly increased
between 2 and 5 months of gestation.
Oogonia
Baker TG, Am J Obstet Gynecol, 1971
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Oogonia to Primary Oocyte Conversion (3 to 5
months gestation)

• Initiation of meiosis (1st step in conversion)
• Meiotic arrest at the diplotene stage
  (end of prophase I)
• Enter the dictyate stage of meiosis
  (prolonged resting until ovulation)
• Proliferation of oogonia by mitosis

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Folliculogenesis
Proliferation
Oocytes
Migration
Genital Ridge
Primordial Follicle
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Oogonia
Hind Gut
Granulosa Cells
Extraembyonic Mesoderm (Epiblasts)
Primordial Germ Cells (PGC)
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Formation of the Primordial Follicle (12th Week)
Immature Oocyte (dictyate stage)
Single layer of flat granulosa cells
Nucleus or Germinal Vesicle
Basal Lamina
Pre-Granulosa cells
Primary Oocyte
Primordial Follicle
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Normal fetal ovary Numerous primordial follicles

• All primordial follicles
• formed by 6-9 months
• Primary oocytes arrested
• in meiotic prophase, not
• capable of mitosis
• No blood supply limited
• exposure to endocrine
• system
• Conversion of squamous
• to cuboidal GCs signals
• start of next growth phase

29 µm
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Primordial to Primary Follicle Conversion
Primordial Follicle
Nobox (/-)
Normal anatomy Normal ovaries Oocytes present
Nobox (-/-)
GDF9 BMP15 ZP1-3 NOBOX
Infertile Atrophic ovaries No oocytes
90 mutation
(Folliculogenesis)
Rajkovic A, Science, 2004
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Histology of Nobox in Deficient Mice
A B Newborn ovaries. GCNA1 binds to oocyte
nuclei within germ cell cysts and primordial
follicles (PF). C D 3-day ovaries. MSY2
stains cytoplasm. Primary follicles (PrF) present
in /- and absent in -/-. E F 7-day old
ovaries. Secondary follicles (SF) present in /-
and absent in -/-. G H 14-day ovaries. Many
secondary follicles in /- and empty follicles
(EF) and degenerating oocytes in -/-.
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Primary Follicle Granulosa cells become
cuboidal, begin to divide very slowly, and
express FSH receptor
Oocyte
1-2 layers of cuboidal granulosa cells
Zona pellucida
Stroma
Germinal vesicle
Basal lamina
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Granulosa cells and the oocyte connect by gap
junctions. Granulosa cells act as nurse cells,
providing nutrients and regulatory molecules to
the oocyte via gap junctions that are essential
for oocyte growth and possibly contribute to
meiotic inhibition during follicle development
Oocyte cytoplasm
Plasma Membrane
Connexin 37
Intracellular Space
Plasma Membrane
Connexin 43
Granulosa cytoplasm
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Proposed mechanism of meiotic inhibition in the
oocyte of the primordial follicle
Granulosa cell
c-AMP
Gap Junction
Oocyte
c-AMP
(-)
PKA
Cyclin B-CDK1
Meiosis
Mehlman LM, Science, 2004
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Proposed mechanism of meiotic inhibition in the
oocyte of the primordial follicle
Granulosa cell
LH
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X
Adenylate Cyclase
c-AMP
GPR3
aGs
aGs
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ß
Orphan receptor
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GDP
GTP
Gap Junction
Oocyte
c-AMP ATP
c-AMP
(-)
PKA
Cyclin B-CDK1
Meiosis
Mehlman LM, Science, 2004
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Secondary Follicle Oocyte and 2-8 layers of
granulosa cells, theca interna and theca cells
Granulosa cells
Zona pellucida
Germinal vesicle
Oocyte
Basal lamina
Theca interna
Theca cells
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Primordial
Transitional
Classic Primary
FSH E2 Receptors Gap junctions
LH prostaglandin receptors
Aromatase activity
GC
Antrum
Oocyte
Oocyte
Secondary
Tertiary (antral)
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The Graafian (Preovulatory) Follicle
Theca Cells
Antrum with follicular fluid
Cumulus granulosa Cells
Basal Lamina
Oocyte
Membrana granulosa Cells
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Classification of Follicles in the Human Ovary
Preantral growth is slow (gt300 days) Antral
growth is more rapid (40-50 days) Selection of
the dominant follicle occurs at 2-5 mm follicle
size
Gougeon A, Endo Rev 1996
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Decline of Oocyte Number during Life
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Follicle Selection
Recruitment
Selection
FSH
Dominant Follicle
0
Day 6
midcycle
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Follicle Selection
Recruitment
Selection
Estrogen
FSH
Dominant Follicle
0
Day 6
midcycle
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Two Cell Concept of Ovarian Steroid Production
Theca Cell
LH
FSH
Cholesterol
R
Androgen
Androgen
R
Androgen
P450arom
Circulation
Estrogen
Estrogen
Granulosa Cell
Follicular Fluid
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The Graafian (Preovulatory) Follicle
Theca Cells
Antrum with follicular fluid
Cumulus granulosa Cells
Basal Lamina
Oocyte
Membrana granulosa Cells
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Morphogenetic Gradient of Apoptosis Through the
Cumulus-Oocyte Complex
Cumulus Cells
Apoptosis
Apoptosis
Oocyte
Denuded Oocyte
Hussein T et al, J Cell Sci, 2006
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Proposed Model of GDF-9/BMP Regulation of
Apoptosis in Cumulus Cells
Hussein T et al, J Cell Sci, 2006
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Role of LH Surge in Ovulation
Ovulation
10-12 hr
Cumulus GCs
LH
34-36 hr
Oocyte
0 7 14 21 28
Mural GCs
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Role of LH Surge in Ovulation
Oocyte maturation Cumulus expansion
Ovulation
10-12 hr
Oocyte Maturation
Cumulus GCs
LH
34-36 hr
Oocyte
0 7 14 21 28
EGF-Like Proteins Aphiregulin Epiregulin Beta-cell
ulin
Mural GCs
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Role of LH Surge in Ovulation
Oocyte maturation Cumulus expansion
Ovulation
10-12 hr
Oocyte Maturation
Cumulus GCs
LH
34-36 hr
EGF Receptor
Oocyte
0 7 14 21 28
EGF-Like Proteins Aphiregulin Epiregulin Beta-cell
ulin
Mural GCs
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Cumulus Expansion
Cumulus granulosa cells
Oocyte
Cumulus-Oocyte Complex
Cumulus expansion
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Processes Leading to Stigma Formation in the
Preovulatory Follicle
Release of proteolytic enzymes
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LH Surge and Progesterone
Lysosomes
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Stigma
Metallo- proteinases
Plasmin
Plasminogen activator
Prostaglandins
Plasminogen

• Oocyte maturation
• Cumulus expansion
• Stigma formation

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Photomicrograph of the ovary surface showing
stigma formation in the ovulating follicle
Stigma
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Ovulation process by which the cumulus-oocyte
complex is released from the follicle.
Cumulus-Oocyte Complex
Stigma
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Corpus Luteum Formation
LH stimulated corpus luteum
FSH stimulated follicle
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Corpus Luteum Function
Theca lutein cells
Granulosa lutein cells
Estrogen
Progesterone
Granulosa lutein cells
Blood vessels
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Hormone Secretion throughout the Menstrual Cycle
Estradiol Progesterone FSH LH
Ovulation
Pregnancy
()
Follicle growth
Hormone Level
Corpus Luteum
0 2 4 6 8 10 12 14 16 18 20
22 24 26 28
Menstrual Cycle Day