Histo - Follicular Development Flashcards
Functions of the Ovary? (2)
gametogenesis (developing gametes formed here (oocytes))
Steroidogenesis –> Estrogens and progesterones
what do estrogens promote? Progesterone?
the growth of internal and external sex organs and female sex characteristics
Progesterone prepares internal sex organs for pregnancy
What’s in the medulla of the ovary?
in the medulla you have loose connective tissue, highly vascularized
you’ll have lymphatic vessels, nerves
What’s in the cortex of the ovary?
in the cortex you’ll find the follicles, which are embedded in richly cellular connective tissue.
what surrounds the cortex of the ovary?
right outside cortex is the tunica albuginia, which is a dense connective tissue
on the outside of the tunica albuginea is germinal epithelium covered with simple squamous to cuboidal mesothelium.
What are the phases to the ovarian cycle?
1) how long does it last
2) 3 phases?
28 days
Follicular phase (folliculogenesis)
Ovulatory Phase
Luteal Phase (formation of corpus luteum)
Follicular phase?
formation of the follicles.. you have a bunch of primordial follicles and then the selection of one mature follicle and that’s the one that will go through ovulation
1) When do the primordial follicles appear?
2) what part of the follicular phase is this?
3) histologically where are they?
4) what is the primordial follicles surrounded by?
5) what is inside it?
6) what is it arrested in?
5th month of development, early growth is independent of hormone stimulation.
first part!
in the stroma just deep to the tunica albuginea
surrounded by a single layer of squamous follicular cells
oocyte
prophase of the first meiotic division
Primary follicle is what?
what is the unilaminar primary follicle stage?
first stage of development of the growing follicle. the oocyte is starting to enlarge so the follicular cells that were originally flat start to become cuboidal.. and when they become cuboidal that’s a primary follicle.
the cells start to secrete proteins that resemble the zona pellucida that separates the oocyte and the follicular cells
Multilaminar primary follicle stage?
1) what is it called physiologically? histologically?
2) what happens to the follicular cells? What are they now called?
3) what else forms?
physiologically its called the secondary follicle, but histologically its still a primary follicle
here the follicular cells start to undergo stratification and form the stratum granulosum.. and the follicular cells are now known as granulosa cells
the zona pellucida and oocyte enlarges
you also have theca interna/externa develop which is right outside the basal lamina of the granulosa cells
Theca Interna:
1) where is it located
2) anything to note about vascularity
3) made up of what?
4) receptors?
5) what does it do?
inner layer and highly vascularized
made of cuboidal secretory cells
has a lot of LH receptors.
synthesize and secrete androgens that are precursors to estrogens.
contains fibroblasts, collagen bundles
What does the theca externa do?
nothing.. just an outer layer of connective tissue.
Secondary Follicle (Tertiary follicle physiologically?)
1) what is it characterized by? How does this happen?
2) what’s more prominent?
characterized by fluid filled antrum –> once the stratum granulosum reaches about 6-12 layers of thickness you get these cavities appearing, and eventually they’ll coalesce to form this antrum
increase in cell layers of zona granulosa
oocyte is larger
Theca Interna is much more prominent
What are some things you’ll see in the secondary follicle? (3)
Antrum
Corona Radiata
Call-Exner Bodies
Graafian follicle (mature follicle)
1) what stage of division has happened but what’s to note about this?
2) what’s different about the stratum granulosum here vs in the secondary follicle or even late primary follicle?
3) what is the thickened mound seen and what does it do?
4) what cells are anchored to the ovary?
5) what are the most internal granulosa cells called?
this is after the first meiotic division has completed but BEFORE ovulation
the antrum increases in size
stratum granulosum (that was getting bigger before) is now getting thinner –> preparing for ejection of the ovum
cumulus Oophorus –> thickened mound which is composed of gradually loosened granulosa cells in prep for ovulation
Corona Radiata –> layer of cells that are firmly anchored to the zona pellucida so they stay during ejection.. they aide in Fallopian tube uptake.`
Mural Granulosa cells –> line the wall of the follicle
thecal layer more prominent.
1) What does LH stimulate the theca interna to do? What can’t they do?
2) what do they do because of this?
3) how is this process initiated?
release androgens. but they lack aromatase so they can’t convert androgens to estrogen.
to do that they’re transported to the granulosa cells.. which DO have aromatase and that’s where they’re further processed.
FSH tells the granulosa cells to convert androgens to estrogens.
What happens to the primary follicles that are not chosen for development?
what mediates it?
most ovarian follicles are lost through follicular atresia, which is mediated by apoptosis of the granulosa cells.
Steps of Follicular Atresia? (7 steps)
1) cessation of what causes the start of it?
Steps:
1) apoptosis within the granulosa cells which is started by the cessation of mitosis.
2) granulosa layer infiltrated by neutrophils and macrophages which break down the zona pellucida.
****3) formation of the glassy membrane (basement membrane of the theca cells separate from follicular cells and increase in thickness, creating the wavy hyaline layer)*
4) invasion of granulosa layer by strands of vascularized CT
5) granulosa cells sloughing into the antrum
6) theca interna cells hypertrophy
7) Collapse of follicle as degeneration continues
8) Invasion of CT into the cavity of the follicle
What kind of oocyte is ejected during the follicular phase? what division does it go through?
what does it remain in until its fertilized?
As the primary oocyte is ejected, it finishes its first meiotic division becoming the secondary oocyte and remain in metaphase of the second meiotic division until its fertilized.
1) what is the ovulatory phase?
2) what is it triggered by?
3) what do you see histologically (what is it called) and how does it rupture?
hormone mediated process resulting in release of 2ndary oocyte from the Graafian follicle
triggered by LH surge
blood flow would stop in a small area of the ovarian surface overlying the bulging follicle –> follicular stigma –> elevates the oocyte then it ruptures
After ovulation, what happens to the theca interna in the follicle?
what is this called?
what happens to prevent more of this loss?
what does it become after the bleeding has stopped?
this is caused from bleeding from the capillaries in the theca interna that go into the lumen
the follicular wall collapses and the region can be filled with blood..
“Corpus Hemorrhagicum” (bleeding corpus luteum)
clotting and fibrosis occurs over the following weeks
Corpus Luteum
What happens during the luteal phase?
1) what is before the corpus luteum?
2) what does the follicular wall look like?
3) what cells go through what?
formation of the corpus luteum.
corpus hemorrhagicum heals, it’ll become the corpus luteum.
the follicular wall is thrown into these deep folds as the follicle collapses.
the cells of the granulosa layer and theca internal cells go through Luteinization
What is Luteinization?
1) what are mural granulosa cells changed to? What do they do?
2) what do theca interna cells become? what do they do?
breakdown of the basal lamina –> invasion of blood vessels –> cell transformation
Mural Granulosa cells are transformed to Granulosa Lutein Cells (80% of the corpus luteum)
synthesize estrogens, progesterone, and inhibin in response to LH and FSH
Theca interna celles –> become theca lutein cells (20% of corpus luteum)
secrete androgens that goes to granulosa cells and progesterone in response to LH DO NOT HAVE AROMATASE
what happens in the absence of fertilization to the corpus luteum?
1) how long does the corpus luteum stay
2) what happens to the cells?
3) what scarring will you see?
remains active for about 14 days, but degenerates 10-12 days after ovulation
the cells become loaded with lipids, decrease in size, and undergo autolysis
formation of a white scar (Corpus Albicans)