Physiology Of The Ovarian Follicle Flashcards
Occurs during embryonic development:
What happens to meiotic arrest (prophase I)?
Meiosis I finishes before ____.
What happens in meiotic arrest (metaphase II)?
Resumption of meiosis II at ____; how?
Elevated levels of cAMP, large antral follicles gain meiotic competence: stay in arrest until LH surge
Ovulation; polar body 1 extruded
Elevated levels of MAPK proteins
Fertilization; rapid degradation of MAPK; polar body 2 extruded
Adult ovary can be divided into two layers
Inner medulla: highly vascular; contains nerves, interstitial cells, lymphatics
Outer cortex: densely cellular stroma; ovarian follicles reside within stroma at different point of development
What is the function of the ovary in the follicular phase of the ovarian cycle?
Ovarian follicle: functional unit
Performs gametogenic and endocrine fx
Pre-menopausal cycling woman contain follicular structures at many different stages
What is the first stage of the ovary during the follicular cycle?
Describe the primordial follicle?
What is it arrested in?
What surrounds it?
What does it release?
What does it represent?
Primordial follicle
Primary oocyte arrested in 1st meiotic prophase
Surrounded by a single layer of pregranulosa cells
Release paracrine factors, no steroid hormones
Represents the ovarian reserve, most undergo atresia
What does the primordial follicle become?
When does the growing preantral follicle develop?
What is the primary follicle?
Why do they increase in size?
What do they produce?
Primary follicle (growing preantral follicle)
Prior to formation of fluid-filled antral cavity
Central primary oocyte; single layer of granulosa cells take on cuboidal shape
Increase in size of follicle due to growth of primary oocyte
Early production of secreted glycoproteins (ZP1, ZP2, ZP3)
What does the primary follicle become?
What is the secondary follicle?
What do they secrete?
What is the difference between the theca cells?
Secondary follicle (growing preantral follicle)
Primary oocyte surrounded by 3-6 layers of cuboidal granulosa cells
Secretion of paracrine factors to induce local stromal cells to differentiate into thecal cells
Theca interna: inner glandular; highly vascular
Theca externa: fibrous-like
What does the follicle need to become a secondary follicle?
Where do they follicles migrate?
What do the follicles release?
What also begins to develop? Fx?
Increased vascularization
From outer cortex to inner cortex, closer to ovarian vasculature
Angiogenic factors that induce the development of 1-2 arterioles; generate vascular wreath around the follicle
Zona pellucida: provides binding sites for the sperm during fertilization
What is maintained n the growing preantral follicle?
___ relationship provides for a nutritional network for growing oocyte.
____ penetrate the zona pellucida and form ____ at the oocyte surface between adjacent granulosa cells.
Contact between the granulosa and oocyte
Avascular
Cytoplasmic processes; gap junctions (basis for communication)
Nutrients, waste, and signals going back and forth between granulosa and oocyte
The growing preantral follicles have ____ endocrine function.
Granulosa cells express what? And do not produce what?
What cells express LH receptors? What is their major product?
Minimal
FSH receptors dependent on paracrine factors from oocyte for growth
Do not produce ovarian hormones at this point
Thecal cells; androstendione (minimal production)
What happens during the preantral to antral transition?
Proliferation of granulosa cells
Continued increase in follicular size
Production of follicular fluid from granulosa cell secretions and thecal vasculature begins to appear between granulosa cells
Fluid drops coalesce to form a singular follicular antrum -> marks beginning of antral phase (cells now dependent on gonadotropins; before it was dependent on paracrine signals)
The appearance of the antrum marks the beginning of the ___ phase.
Increase in the follicular size depends on what?
Oocyte becomes suspended in what?
Antral
Increase in antral size, volume of follicular fluid, proliferation of granulosa cells
Fluid surrounded by a dense mass of granulosa cells (cumulus oophorous and corona radiata)
What happens in antral phase?
What two types of granulosa cells develop? What is their fx?
Increase in granulosa cells
Mural granulosa (stratum granulosum): outer wall of follicle; becomes highly steroidogenic (produce estrogen and progesterone); become the corpus luteum
Cumulus cells (cumulus oophorus/corona radiata): maintain gap and adhesion junctions with oocyte; released during ovulation with oocyte
Growth at the antral stage becomes responsive to ___.
What do the theca interna cells respond to? What is their fx?
What do the granulosa cells respond to? What is their fx?
Gonadotropins
LH; Synthesize androgens from acetate and cholesterol; produce androstenedione
FSH; convert androstenedione from thecal cells to estradiol using aromatase; induces expression of LH receptors in late follicular phase
Oocyte grows ___ in the early stages of antral follicles; growth ____ in larger follicles
At antral stage, oocyte becomes competent to complete ____.
However, larger antral follicles stay arrested in ____ until ____.
Meiotic arrest achieved by maintenance of _____ in the mature oocyte
Rapidly; slows
Meiosis I at ovulation
Meiosis I; midcycle LH surge
Elevated cAMP levels
What follicles are recruited to being development each monthly cycle?
When is one dominant follicle selected?
How is it selected?
What happens to the other follicles?
Several large antral follicles
Early follicular phase
Largest follicle with most FSH receptors (highest sensitivity) becomes dominant follicle
Undergo atresia/ apoptosis of oocytes and granulosa cells
