36.2.3 - Oogenesis / Ovarian cycle Flashcards
Function - Stimulating the follicle – Growth during the follicle phase
Produces / Releases - Anterior Pituitary
Stimulates Release - Negative Feed Back Loop -
Low Levels Estradiol
Peak - 0-13 Days
FSH - Follicle-stimulating Hormone
Function - Trigger Ovulation (release of mature egg from ovary) formation of corpus luteum
Produces / Releases - Anterior Pituitary
Stimulates Release - Negative Feed Back Loop -
Low Levels Estradiol
Peak - 0-13 Days
LH - Luteinizing hormone
Function - Follicle growth, Female Sex characteristics, Buildup of uterine lining
Produces / Releases - Cells in Follicle
Stimulates Release - Negative Feed Back Loop - Low Levels Estradiol (Buildup of uterine lining)
Positive feedback from rising estrogen levels (surge in GnRH and releases of LH)
Peak - Day Around day 13 (Just before ovulation occurs)
Estrogen / Estradiol
Function - Prepares uterine lining from fertilized egg and maintains corpus luteum
Produces / Releases - Corpus Luteum after ovulation
Stimulates Release - Rising LH levels during luteal phase
Peak - Luteal phase after ovulation
Progesterone
3 Phases of the Ovarian Cycle
(Slide 4)
Follicular
Ovulation
Luteal
Follicular
Negative Feedback suppressing LH and FSH (0-13 Days)
-Follicles in the Ovary begin to develop
-As they grow, more estrogen (estradiol) is released
-Sets Stage for ovulation
Luteal
Second half of menstrual cycle (15-20)
-Corpus Luteum forms (after ovulation) and secrete progesterone
-If fertilized corpus luteum is maintained / otherwise, it degrades (no fertilization)
The luteal phase supports early pregnancy (preparation for the next cycle)
Ovulation
Release of the oocyte into the fallopian tube (Around 13)
-Triggered by high Levels of LH
-Allows egg to become fertilized
High estrogen–positive feedback stimulates FSH and LH (luteal phase)
The hypothalamus is stimulated by high levels of estradiol (estrogen)
Precisely time ovulation allowing the egg to be fertilized (Increase the amount of LH / Surge to trigger ovulation)
ALLOWS HORMONE LEVELS TO FLUCATE
Feed Back Loop Positive
(Slide 5 / 7)
Progesterone - Estrogens = Negative Feedback
Low Estrogen – negative feedback suppressing LH and FSH (follicular phase)
The hypothalamus and Pituitary are inhibited by low levels of estradiol/progesterone.
Prevent overstimulation of ovaries
Feedback Loop Negative
(Slide 6 / 7)
If no pregnancy
The Corpus Luteum degenerates in 2nd half of the luteal phase.
Estrogen & Progesterone levels go down = shedding of uterine lining (menstrual period)
If pregnancy
Implants in the uterine lining
Embryo secrets HCF (human chorionic gonadotrophin
HCG stimulates the growth of the corpus luteum
Estrogen and Progesterone levels rise = growth of uterine lining and other pregnancy-related changes
