Ovulation Cycle Flashcards
What are two functions of the ovaries?
1) Store oocytes
2) Produce hormones
What are the four types of cells in the ovary?
1) Granulosa 2) Theca - make androgens which make estrogen 3) Stromal maintain estrone 4) Luteal make progesterone some estrogen and inhibin
Where is GnRH releaesd from?
The hypothalamus
Where is LH and FSH released from?
The pituitary gland
What hormones communicate with the pituitary gland and the hypothalamus to give feedback?
Progesterone and Estrogen
Slow GnRh release favours FSH or LH?
Slower GnRH release favours the secretion of FSH, which makes the ovaries develop follicles
Fast GnRH release favours FSH or LH?
Fast GnRH release favours LH release which triggers the body to develop follicles and make the corpus luteum.
What does inhibin do?
It slows down the secretion of FSH.
What do high levels of estrogene do in terms of feedback?
Estrogen (without progesterone) stimulates high pulse frequency GnRH, LH and FSH release (positive feedback)
There are 3 different types of estrogen, how are they different from one another?
1) Estrone (E1) - it’s weak. Made in ovaries and fat cells. Continues in menopause
2) Estrodiol (E2) - Most abundant in reproductive years. Made in ovaries, adrenal glands, liver, breast and fat cells. Decreases in menopause.
3) Estriol (E3) produced by the placenta during pregnancy.
What is FSH’s main job?
Promotes growth of follicles. Granulosa (cells surrounding the oocyte) and theca cells (the cells surrounding the granulosa cells) have FSH receptors.
What does LH work on and what does it do?
LH stimulates theca cells to make androgens which diffuse to granulosa cells that contain aromatase (activated by FSH).
What happens in the early follicular phase?
FSH promotes the growth of follicles, LH stimulates theca cells to make androgens like aromatase and therefore estradiol
What happens in the late follicular phase?
Granulosa cells release inhibin which inhibits FSH release. Estradiol levels increase. GnRH pulse frequency increases which favours LH release. LH stimulates theca cells to continue androgen synthesis and granulosa cells produce a bit of progesterone.
How does the dominant follicle get chosen?
It is the one that makes the most estradiol and some progesterone compared to the other developing follicles
What hormones are high during ovulation?
LH, GnRh, FSH, Estradiol, and progesterone kinda starts to get going .
What happens during ovulation?
The first meiotic division is completed forming the secondary oocyte. The follicle fills with fluid. Progesterone, proteolytic enzymes and prostaglandings trigger follicle rupture and an oocyte gets released.
How does body temperature relate to ovulation?
3 days of elevated body temperature means ovulation has occurred.
How does clomiphene citrate (aka clomid or serophene) which are all fertility drugs work?
They block estrogen receptors in the hypothalamus (SERM) which inhibits the negative feedback of estrogen on GnRH release. This causes the pituitary gland to make more FSH and LH which increases recruitment of follicles and stimulates ovulation.
What happens in the proliferative phase?
1) The endometrium grows - glands and arteries grow to feed the endometrium and make it viable for life
2) Progesterone receptors get upregulated and become more sensitive to progesterone.
What do granulosa and theca cells become under the influence of LH to form the corpus luteum?
Luteal cells.
What hormones are released from the corpus luteum?
Progesterone mainly, and estradiol, and inhibin.
What happens to FSH and LH release after ovulation?
They decrease. GnRH pulse does frequent LH. Follicle growth is suppressed.
Where is HCG released from?
In the event of fertilization, HCG gets released from cells of the blastocyst which prevents corpus luteum degeneration. The corpus luteum will produce it’s own hormones for 3 months until the placenta is fully functional.
