Quiz 4 Lecture Notes Flashcards
Stages in the formation of a follicle
- primordial follicle
- primary follicle
- secondary follicle
- tertiary follicle
- Graafian follicle
antral follicles
- tertiary follicle
- graafian follicle
primordial follicle
1 layer of granulosa cells, flat cells
primary follicle
1 layer of granulosa cells, cuboidal
secondary follicle
2+ layers of granulosa cells, cuboidal shape, theca cells start to form
tertiary follicle
antrum starts to form, increase in size, 2 types of theca cells begin to make layers
graafian follicle
antrum is large, cumulus oophorus, theca layers
gonadotropin independent stages of folliculogenesis
- primordial
- primary
- secondary
gonadotropin dependent stages of folliculogenesis
- tertiary
- graafian follicle
Primordial Follicle Formation
- notch signaling
- Nobox
- Figla
Primordial to Primary Follicle Transition
- Fox12
- Nobox
- Sphlh 1 and 2
- Lhx8
Primary to Secondary Follicle Transition
- GDF9 (growth differentiation factor 9) !!!
- kit 1
- kit (receptor)
Secondary to Antral Follicle Transition
- FSH and FSH receptor !!! (gonadotropin dependent)
- Inha
- Igf1
- Ccnd2
- Foxol/3
- Smad3
- Taf46
Antral (teriary) to Preovulatory (graffian) Follicle Transition
- esr 1 and 2 !! (estradiol receptor)
- acvr2a
- gja4 (gap junction protein)
- connexins (gap junction protein)
follicular / oocyte communication
gap junctions are formed through the zona pellucida so that the cytoplasm can move nutrient between the granulosa and the oocyte
what is an example of something that travels through the gap junctions for follicular / oocyte communication?
GDF9 is secreted from the oocyte to add more layer of granulosa cells, must go through gap junctions
bidirectional communication of the cumulus cells and oocyte
gap junctions and paracrine communication
bidirectional communication: cumulus cells to oocyte
- kit - ligand
- FF-MAS
- EGF
bidirectional communication: gap junctional
- cAMP
- metabolites
- amino acids
bidirectional communication: oocyte to cumulus cells
GDF9
GDF9
secreted by the oocyte, required for follicular development past primary stage
Role of the oocyte in follicle growth
- secretes GDF9
- affects granulosa cell differentiation
- affects energy and metabolic function of granulosa cells
- can increase follicle cell growth and division
- produces proteins to form zona pellucida
follicle development: dogma
around the time of birth, the female is equipped with the number of germ cells for the rest of her life
menopause
no longer has oocytes to ovulate
why is there a big drop in the number of gametes after puberty?
females have a limited number of gametes, after puberty, follicles will begin to either ovulate or degenerate
atresia
programmed cell death
briefly explain the two-cell, two-gonadotropin model
the hypothalamus produces GnRH which tell the anterior pituitary to produce LH and FSH, LH stimulates theca cells to make testosterone and FSH stimulates the granulosa cells to make testosterone into estrogen, the high estrogen and LH surge cause ovulation, estrogen has negative or positive feedback on the hypothalamus and negative feedback on the pituitary with inhibin
gonadotropin independent
initial development, no gonadotropins
gonadotropin responsive
follicles can respond to gonadotropins but gonadotropin stimulus is not required for follicle growth
gonadotropin dependent
follicles have been stimulated to grow towards ovulation, (recruited, selected, dominant), post puberty, if gonadotropin is removed it will result in atresia
two stages of follicular recruitment
- initial recruitment
- cyclic recruitment
initial recruitment
primordial follicular pool recruited into the pool of growing follicles in a continuous manner (gonadotropin independent)
recruitment for follicles to GROW
cyclic recruitment
astral follicles are recruited to grow towards ovulation during a specific estrous cycle (gonadotropin dependent)
grow to potentially OVULATE
Follicular Wave 1
- recruitment, selection, dominance, atresia
- mature CL is present, makes progesterone which will have a negative feedback on LH so the follicle will degenerate
the hormone of ovulation
LH
LH functions
- ovulation
- CL formation
Follicular Wave 2
- recruitment, selection, dominance, ovulation
- no CL, high levels of LH
follicular recruitment
follicles begin to grow
follicular selection
3-4 follicles chosen, the best
follicular dominance
one follicle is chosen
__________ inhibits FSH through negative feedback
estrogen
FSH
follicle stimulating hormone
LH
luteinizing hormone
when FSH reaches its peak in the cell, what will occur? Why does FSH start to decrease after this?
- follicle wave will start
- follicles begin to produce estrogen which inhibits FSH
endocrine explanation: recruitment
- entry into gonadotropin sensitive pool
- FSH needed to recruit follicles
- estrogen must be low
- LH low
endocrine explanation: selection
- follicles are selected, ovulatory follicles emerge
- estrogen increases
- FSH levels begin to decrease
- LH begins to increase
endocrine explanation: dominance
- final growth of ovulatory follicles and inhibition of others
- develop LH receptor
- rely on LH (NOT FSH)
2 fates of recruitment
- selected for continued growth
- atresia
2 fates of dominance
- ovulation (low progesterone)
- atresia (high progesterone)
3 steps of oogenesis
- primordial germ cell (mitosis)
- oogonia (meiosis)
- oocyte (goes into arrest around birth)
meiotic arrest
when does it occur? what must be maintained?
- around birth, until it is chosen to be a dominant follicle
- maintaining a high level of cAMP
3 ways the cell maintains cAMP during meiotic arrest
- cAMP production inside the oocyte
- cAMP comes from the granulosa cells
- cGMP from granulosa cell inhibits phosphodiesterase enzyme (PDE)
ovulation
product of a follicle that continues growing, meiosis must be complete, and oocyte is mature
how does a surge of LH cause ovulation to occur?
surge of LH inhibits the oocytes connection to the cumulus cell, this prevents cAMP and cGMP so that the follicle is no longer under arrest so it can finish maturing
oocyte meiotic maturation
chromosomes are divided in the cell, one part remains in the egg the other creates a polar body
polar body
half of the original DNA from the oocyte, no longer a part of the oocyte
metaphase 2 arrest
after the polar body is created the cell is in arrest until fertilization, it is broken by a calcium rise initiated by the fertilizing sperm (if it is not fertilized it will degenerate)
Mammalian Ovulation Theories
- Pressure Theory
- Smooth Muscle Contaction
- Thinning of the Follicular Wall
Mammalian Ovulation Theories: pressure theory
pressure inside (and outside the cell, blood pressure) increases as it grows and will eventually erupt
Mammalian Ovulation Theories: smooth muscle contraction
the follicle is surrounded by smooth muscle, when it contracts in assists the follicle in ovulation
Mammalian Ovulation Theories: thinning of the follicular walls
enzymes (collagenase) eat at the wall, thinning it, the thinner the wall the easier it is for ovulation to occur
important regulators in ovulation
- LH and LH receptor !!
- prostoglandins
- progesterone
- epidermal growth factor (EGF)
- oocyte
