Ovaries
• Ovaries are almond shaped bodies
3cm long, 1.5 wide and 1cm thick
• Ovaries are covered externally by
Cuboidal Germinal Epithelium that
is continuous with overlying
Mesothelium of Tunica Vaginalis
and underlying fibrous capsule of
Tunica Albuginea
• Ovary can arbitrarily be divided
into the Cortex with dense
connective stroma and Medulla with
looser connective tissues and
blood vessels located in the
center starting from the
mesovarium
◦ It is worth noting that there
is no distinct border between
the ovarian medulla and cortex
• Within the ovary there can be seen
various Follicles at various
stages of differentiation
◦ Primary and Secondary Follicles
◦ Mature Follicles
• Other structures:
◦ New and Old Corpus Albicans
◦ Atretic Follicles
◦ Corpus Luteum
Derived from Primordial Germ cells
from the yolk sack form Oogonia
which enter meiosis I and become
arrested in the Diplotene Stage of
Prophase I forming Primary Oocytes
• There are 300,000 Oocytes at
puberty
• Throughout a females life, 450
Oocytes are liberated
• Remaining undergo Atresia and form
Atretic Follicles
DIFFERENT STAGES OF OOCYTE & FOLLICULAR
DEVELOPMENT
1. Primordial Ovarian Follicle
• Central Oocyte
• Single Layer of Basal Follicular Cells
• External layer of Cortical Stromal Cells
• The maturation of Primordial follicles occurs at puberty when FSH Stimulates their
maturation and follicular growth.
• The determination of which primordial follicle will be chosen for maturation during
each month is dependent on:
◦ Complex hormonal balances
◦ Differences among FSH Receptor Numbers, Estrogen Synthesis
◦ Other Minute Variables
◦
, 2. Unilaminar Primary Follicle
• Follicular Cell
undergo mitosis to
form a cuboidal
unilaminar follicular
layer
• The Nucleus and
closely located
organelles become
larger
• The follicle itself enlarges
3. Multilaminar Primary Follicle
• Follicular Cells undergo further
mitosis and form the Granulosa layer
• Zona Pellucida between the oocyte and
Granulosa layer develops.
◦ Zona Pellucida contains:
‣ ZP3 and ZP4 sperm receptors
‣ Receptor for Acrosomal
Specific Proteins that
activate Acrosomal Enzymes
◦ Communication exist between the oocyte and Granulosa layer
through Gap Junction in the Zona Pellucida
• Development of the Thecal Layer can also be observed
◦ Theca is divided into 2 distinct layers:
‣ Theca Interna which contain FSH Dependent steroid producing cells that
ultimately produce Estrogen and Estradiol
‣ Theca Externa which is a more fibromuscular layer composed of smooth muscle
cells and fibroblasts
• Ovaries are almond shaped bodies
3cm long, 1.5 wide and 1cm thick
• Ovaries are covered externally by
Cuboidal Germinal Epithelium that
is continuous with overlying
Mesothelium of Tunica Vaginalis
and underlying fibrous capsule of
Tunica Albuginea
• Ovary can arbitrarily be divided
into the Cortex with dense
connective stroma and Medulla with
looser connective tissues and
blood vessels located in the
center starting from the
mesovarium
◦ It is worth noting that there
is no distinct border between
the ovarian medulla and cortex
• Within the ovary there can be seen
various Follicles at various
stages of differentiation
◦ Primary and Secondary Follicles
◦ Mature Follicles
• Other structures:
◦ New and Old Corpus Albicans
◦ Atretic Follicles
◦ Corpus Luteum
Derived from Primordial Germ cells
from the yolk sack form Oogonia
which enter meiosis I and become
arrested in the Diplotene Stage of
Prophase I forming Primary Oocytes
• There are 300,000 Oocytes at
puberty
• Throughout a females life, 450
Oocytes are liberated
• Remaining undergo Atresia and form
Atretic Follicles
DIFFERENT STAGES OF OOCYTE & FOLLICULAR
DEVELOPMENT
1. Primordial Ovarian Follicle
• Central Oocyte
• Single Layer of Basal Follicular Cells
• External layer of Cortical Stromal Cells
• The maturation of Primordial follicles occurs at puberty when FSH Stimulates their
maturation and follicular growth.
• The determination of which primordial follicle will be chosen for maturation during
each month is dependent on:
◦ Complex hormonal balances
◦ Differences among FSH Receptor Numbers, Estrogen Synthesis
◦ Other Minute Variables
◦
, 2. Unilaminar Primary Follicle
• Follicular Cell
undergo mitosis to
form a cuboidal
unilaminar follicular
layer
• The Nucleus and
closely located
organelles become
larger
• The follicle itself enlarges
3. Multilaminar Primary Follicle
• Follicular Cells undergo further
mitosis and form the Granulosa layer
• Zona Pellucida between the oocyte and
Granulosa layer develops.
◦ Zona Pellucida contains:
‣ ZP3 and ZP4 sperm receptors
‣ Receptor for Acrosomal
Specific Proteins that
activate Acrosomal Enzymes
◦ Communication exist between the oocyte and Granulosa layer
through Gap Junction in the Zona Pellucida
• Development of the Thecal Layer can also be observed
◦ Theca is divided into 2 distinct layers:
‣ Theca Interna which contain FSH Dependent steroid producing cells that
ultimately produce Estrogen and Estradiol
‣ Theca Externa which is a more fibromuscular layer composed of smooth muscle
cells and fibroblasts
