Antral And Tertiary Follicle Formation

Question 1

The continued development of the oocyte to a mature state capable of being fertilized is

Answer 1

dependent upon the hormones of the menstrual cycle.

Question 2

FSH stimulates a further increase in

Answer 2

GC numbers and is responsible for the formation of a fluid filled space within the growing follicle.

Question 3

Fluid accumulation between cells commences when the follicle diameter reaches about

Answer 3

200-300 uM and these fluid-filled cavities coalesce to form a single cavity leading to a dramatic increase in follicular size.

Question 4

6th week of fetal development: primordial germ cells (oogonia) migrate to

Answer 4

the ovarian cortex and multiply by mitosis.

Question 5

Follicle assembly:

Answer 5

some oogonia are encapsulated by follicular cells → primordial folicle.

First stage of meiotic division arested > primary oocyte.

Question 6

Then there is birth:

Answer 6

No further development until sexual maturity.

Question 7

Upon sexual maturity:

Answer 7

Secretion of pituitary gonadotropins FSH and LH.

Primordial follicle activation: selected cohorts recruited to develop.

Follicular growth: increase in granulosa and cell number.

Steroidogenesis: increasing secretion of estrogen progressively inhibits the release of FSH and promotes LH release.

Question 8

Upon ovulation, Corpus luteum formation:

Answer 8

progesterone secretion by corpus luteum maintained by low levels of LH.

Question 9

Progesterone inhibits the expression of high levels of

Answer 9

LH secretion.

Question 10

Following fertilization and implantation, Corpus luteum of pregnancy maintained by

Answer 10

HCG secreted by the developing conceptus.

Question 11

Primordial follicle:

Answer 11

single layer of flattened granulosa cells.

Question 12

Primary follicle:

Answer 12

single layer of cuboidal granulosa cells.

Question 13

Secondary follicle:

Answer 13

two layers of granulosa and thecal cell differentiation.

Question 14

Antral follicle:

Answer 14

fluid-filled antrum develops.

Question 15

Graafian follicle:

Answer 15

mature follicle with distinct granulosa cells populations; mural and coronal.

Question 16

The antrum grows by accumulating fluid derived from blood flowing through the thecal capillaries and secretion products from

Answer 16

follicular cells some of which (e.g. hyaluron and proteoglycans) create an osmotic gradient that participates in antrum growth.

Question 17

Follicular fluid is thus a product of

Answer 17

transudation of plasma and secretions from the GC.

Question 18

Cytokines are small- to medium-size proteins/glycoproteins that act

Answer 18

as intercellular mediators and growth factors.

Question 19

Intrafollicular cytokines that regulate angiogenesis, steroidogenesis, oocyte maturation, leucocyte infiltration and follicle rupture/remodeling during ovulation are

Answer 19

readily detectable in follicular fluid

Question 20

As the follicle size increases, the thecal layer

Answer 20

differentiates into the theca interna and theca externa.

Question 21

The GC and theca become highly active steroidogenic cells. Under the influence of FSH and LH the

Answer 21

GCs continue to divide and more fluid fills the antrum.

Question 22

The theca interna becomes increasingly

Answer 22

vascularized as follicle development ensues while the GC layer remains avascular.

Question 23

As the volume of the antrum increases

Answer 23

the GCs become pressed against the wall of the follicle and are termed mural GCs.

Question 24

The oocyte is also eccentric and is attached to the mural GC by a stalk of

Answer 24

avascular GCs, the cumulus oophorus, and originate from a common progenitor in pre-antral follicles.

Question 25

Antrum formation brings about physical

Answer 25

separation and differentiation of the two cell compartments.

Question 26

The cumulus oocyte complex (COC) is comprised of three to four layers of cumulus cells (approximately 2000 cells) that

Answer 26

envelope the oocyte in tightly packed concentric layers.

Question 27

Removal of the cumulus cells, even in the very final hours of maturation, oocytes will

Answer 27

severely compromise the ooyctes competence to fertilize.

Question 28

Oocyte paracrine signaling to cumulus cells is

Answer 28

essential for cumulus expansion.

Question 29

Two oocyte secreted morphogens, GDF9 and bone morphogenic protein 15 (BMP15) regulate

Answer 29

cumulus gene expression.

Question 30

The GC immediately surrounding the oocyte, the corona radiata, are intimate connected to the oocyte via

Answer 30

specialized gap junctions that allow for nutrient exchange and transport of signaling molecules that regulate oocyte activity between the oocyte and GC.

Question 31

The follicle is now called the tertiary Graafian or preovulatory follicle:

Answer 31

the follicle has increased from less than 0.1 mm as a newly recruited primary follicle to a 12-19 mm preovulatory follicle

Question 32

Since the follicles are physically located within the ovarian cortexthis dramatic increase in the size ultimately leads to

Answer 32

one of the surfaces of the follicle coming in contact with the tunica albuginea.

Question 33

The oocyte volume increases during follicle development but its genetic maturation

Answer 33

remains unchanged as a primary oocyte.

Question 34

Recent evidence has demonstrated a functional role for the estradiol:

Answer 34

estrogen receptor system in follicular GC maintaining oocyte meiotic arest by regulating the expression of natriuretic peptide C (NPPC) and natriuretic peptide receptor 2 (NPR2).

Question 35

Cyclic GMP diffuses into the oocyte via the large

Answer 35

network of gap junctions and inhibits phophodiesterase 3A (PDE3A) suppressing the hydrolysis of cyclic AMP.

Question 36

High levels of cAMP in the oocyte suppress the activation of

Answer 36

MPF via the action of cAMP-dependent protein kinase A (PKA).

Question 37

The maturing follicle begins to bulge on the ovarian surface forming a thinned area that looks like a blister (the stigma) from which the

Answer 37

oocyte will leave the ovary following rupture of the follicle at ovulation.

Question 38

The anterior pituitary releases a surge of LH around Day 14 of a 28-day menstrual cycle. However, cumulus cells express few, if any, receptors for LH and hence the mechanism by which LH induced

Answer 38

cumulus cell expansion and oocyte maturation remain elusive.

Question 39

This surge of LH is responsible for

Answer 39

the resumption of meiosis I and the ovulatory process.

Question 40

After ovulation, the mature oocyte arrested in metaphase of meiosis II is picked-up by

Answer 40

the fimbria of the oviduct and transported to the distal 1/3 of oviduct (ampula).

Question 41

Candidate regulatory factors include EGF-ike growth factors (such as amphiregulin, epiregulin and betacelulin) that have been shown to play critical roles in

Answer 41

mediating the actions of LH in pre-ovulatory follicles.

Question 42

Amphiregulin is the dominant EGF-like molecule in humans and its presence in the follicle is stimulated

Answer 42

by the LH surge.

Question 43

Amphiregulin activates EGF receptors within the follicle that trigger oocyte nuclear maturation, likely by autocrine and paracrine mechanisms, to propagate the LH signal to

Answer 43

granulosa and cumulus cells stimulating cumulus expansion, oocyte maturation and ovulation.

Question 44

RAS and MAPK also appear to have important signaling roles in

Answer 44

ovarian follicles at the time of ovulation.

Question 45

Reinitiation and completion of the second meiotic division is triggered by

Answer 45

fertilization and completes the process of oogenesis.

Question 46

However, this final stage of oogenesis is short-lived. The 23 maternal chromosomes will join the 23 paternal chromosomes of the sperm within 18 hours by the process of

Answer 46

syngamy to form the diploid embryo.

Question 47

In most menstrual cycles, only one follicle will continue to develop to the fully mature graafian stage (dominant follicle selection). The majority of growing follicles will undergo

Answer 47

atresia at some point during development involving degradation of all cell types in the follicle that appears to commence with different cell populations depending on the stage of follicle development at the time of atresia.

Question 48

The oocyte is the first component to die in pre-antral bovine follicles whereas

Answer 48

the granulosa cells die first in later stage follicles.

Question 49

Thecal cells appear to be more susceptible to cell death during

Answer 49

earlier stages of follicle development.

Question 50

Death of follicular cells reportedly occurs by

Answer 50

programmed cell death (apoptosis)) as well as autophagy, necrosis and cornification.