Ovulation

Question 1

what do oocytes develop within

Answer 1

ovarian follicles

Question 2

describe folliculogenesis

Answer 2

growth and maturation of follicle and oocyte >1year

Question 3

when do primordial follicles mature

Answer 3

sporadically on a daily basis from time of puberty onwards

Question 4

how many follicles ovulate and what happens if they dont

Answer 4

most never ovulate
they die through atresia

Question 5

describe atresia with follicles

Answer 5

hormonal feedback with maternal hormones
whereby a few follicles become dominant and survive
vast majority die

Question 6

what are the endocrine sensing components of the ovarian follicle

Answer 6

granulosa cells
theca cells

Question 7

folliculogenesis and ovulation are controlled by…

Answer 7

neuroendocrine feedback network

Question 8

the pituitary gland produces _______ which controls folliculogenesis

Answer 8

follicle stimulating hormone (FSH)

Question 9

the pituitary gland produces _______ which controls ovulation

Answer 9

luteinising hormone (LH)

Question 10

what acts on the pituitary gland to stimulate FSH and LH release

Answer 10

gonadotrophin releasing hormone GnRH from hypothalamus (brain)

Question 11

what produces hormones that act back on pituitary gland to control FSH and LH release

Answer 11

maturing follicles in ovary

Question 12

follicle growth promoted by ___ hormone

Answer 12

FSH

Question 13

_____ & ______ produced as follicle grows

Answer 13

oestrogen and progesterone

Question 14

oestrogen and progesterone produced as follicle grows acts on _____ & ____

Answer 14

uterine endometrium and pituitary

Question 15

what does oestrogen acting on pituitary stimulate

Answer 15

LH surge

Question 16

oestrogen and progesterone stimulate uterine endometrium to?

Answer 16

become receptive for implantation

Question 17

what does LH surge from pituitary trigger

Answer 17

ovulation at the mid cycle

Question 18

(response in ovary to LH surge) what do granulosa cells express & their relative function

Answer 18

LH receptor - to sense LH surge coming from pituitary

Question 19

(response in ovary to LH surge) in response to sensed LH surge from granulosa cells what happens

Answer 19

progesterone receptor gene is induced in granulosa - critical for ovulation

Question 20

what does LH induce expression of in granulosa cells

Answer 20

epidermal growth factor-ligands (Egf-L)

Question 21

function of Egf-L

Answer 21

• 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

Question 22

what else is important for cumulus response besides Egf-L

Answer 22

oocyte secreted factors
form cumulus oocyte complex

Question 23

describe cumulus oocyte complex (COC)

Answer 23

• in response, specialised extracellular matrix synthesised around oocyte
• production of extracellular matrix causes expansion of cumulus oocyte complex

Question 24

importance of cumulus oocyte complex (COC)

Answer 24

• genes that comprise matrix are very important for ovulation
• deletion of any genes involved in matrix will cause severe subfertility or infertility

Question 25

what is induction of progesterone receptor in granulosa cells important for

Answer 25

controls expression over 200 genes that mediate follicle rupture and release of the oocyte (COC)

Question 26

what can progesterone antagonists such as Ulopristal acetate do

Answer 26

block ovulation
- used in some emergency contraceptives

Question 27

how do epidermal like growth factors (EGF-L) activate oocyte meiotic maturation

Answer 27

causes changes in cyclic nucleotides (cAMP, cGMP) in oocyte which lead to resumption of oocyte meiosis (releases inhibition on meiosis promoting factor)

Question 28

describe stages before and after oocyte meiosis resumption and the resulting products

Answer 28

• 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

Question 29

describe one progesterone receptor dependent gene

Answer 29

• protease gene for ADAMTS1
• deletion of gene shown important for number of oocytes released and successful pregnancy rate

Question 30

COC carrying mature oocyte penetrates thru follicular apex and enters fallopian tube where can interact with _______ and _________ occurs

Answer 30

sperm
fertilisation