Ovulation Flashcards
what do oocytes develop within
ovarian follicles
describe folliculogenesis
growth and maturation of follicle and oocyte >1year
when do primordial follicles mature
sporadically on a daily basis from time of puberty onwards
how many follicles ovulate and what happens if they dont
most never ovulate
they die through atresia
describe atresia with follicles
hormonal feedback with maternal hormones
whereby a few follicles become dominant and survive
vast majority die
what are the endocrine sensing components of the ovarian follicle
granulosa cells
theca cells
folliculogenesis and ovulation are controlled by…
neuroendocrine feedback network
the pituitary gland produces _______ which controls folliculogenesis
follicle stimulating hormone (FSH)
the pituitary gland produces _______ which controls ovulation
luteinising hormone (LH)
what acts on the pituitary gland to stimulate FSH and LH release
gonadotrophin releasing hormone GnRH from hypothalamus (brain)
what produces hormones that act back on pituitary gland to control FSH and LH release
maturing follicles in ovary
follicle growth promoted by ___ hormone
FSH
_____ & ______ produced as follicle grows
oestrogen and progesterone
oestrogen and progesterone produced as follicle grows acts on _____ & ____
uterine endometrium and pituitary
what does oestrogen acting on pituitary stimulate
LH surge
oestrogen and progesterone stimulate uterine endometrium to?
become receptive for implantation
what does LH surge from pituitary trigger
ovulation at the mid cycle
(response in ovary to LH surge) what do granulosa cells express & their relative function
LH receptor - to sense LH surge coming from pituitary
(response in ovary to LH surge) in response to sensed LH surge from granulosa cells what happens
progesterone receptor gene is induced in granulosa - critical for ovulation
what does LH induce expression of in granulosa cells
epidermal growth factor-ligands (Egf-L)
function of Egf-L
- act on cumulus cells
- transmit ovulatory signal to cumulus cells that don’t express LH receptor
- cumulus cells then respond by activating expression of extracellular matrix genes
=> undergo cumulus expansion (COC expansion) & activate oocyte meiotic maturation
what else is important for cumulus response besides Egf-L
oocyte secreted factors
form cumulus oocyte complex
describe cumulus oocyte complex (COC)
- in response, specialised extracellular matrix synthesised around oocyte
- production of extracellular matrix causes expansion of cumulus oocyte complex
importance of cumulus oocyte complex (COC)
- genes that comprise matrix are very important for ovulation
- deletion of any genes involved in matrix will cause severe subfertility or infertility
what is induction of progesterone receptor in granulosa cells important for
controls expression over 200 genes that mediate follicle rupture and release of the oocyte (COC)
what can progesterone antagonists such as Ulopristal acetate do
block ovulation
- used in some emergency contraceptives
how do epidermal like growth factors (EGF-L) activate oocyte meiotic maturation
causes changes in cyclic nucleotides (cAMP, cGMP) in oocyte which lead to resumption of oocyte meiosis (releases inhibition on meiosis promoting factor)
describe stages before and after oocyte meiosis resumption and the resulting products
- meiosis arrested in prophase I from birth up until this point
- resumes meiosis I arrests in meiosis II metaphase -> ready for fertilisation
- from resumption of meiotic maturation, there’s extrusion of first polar body containing half of chromosomes
describe one progesterone receptor dependent gene
- protease gene for ADAMTS1
- deletion of gene shown important for number of oocytes released and successful pregnancy rate
COC carrying mature oocyte penetrates thru follicular apex and enters fallopian tube where can interact with _______ and _________ occurs
sperm
fertilisation
