At birth, all oogonia have developed into….
Primary Oocytes and are arrested in prophase 1 (until ovulation)
When do oocytes complete meiosis I?
Complete meiosis I at ovulation and are arrested in metaphase II until fertilization
What has to happen in order for the oocytes to complete Meiosis II?
Fertilization!
Describe the development of an occyte, starting with primordial follicle
Primordial follicle Primary follicle Secondary Follicle Graafian Follicle - OVULATION Corpus Luteum left in ovary
What is menopause?
follicle in ovary are exhausted, decreased estrogen production
What determines the dominant follicle?
The biggest one, that is producing the most hormones
What does FSH do?
Stimulates follicle development
LHR synthesis
What are the two products of the granulosa cell?
Inhibin = inhibits FSH production in anterior pituitary
Estrogen = inhibits GnRH and Ant. pit UNTIL it reaches a threshold, and then turns to positive feedback to create the LH surge
Why does LH surge, but not FSH?
Inhibin produced by the granulosa cells is inhibiting FSH production (because at this point you don’t need any more follicles developing!!)
Main function of LH?
to induce ovulation!!
The LH surge
**ovulation required for formation of the corpus luteum
In the first trimester, what hormone maintains the corpus luteum?
hCG maintains corpus luteum - which keeps progesterone levels high to maintain pregnancy
hCG acts on what receptor?
Lutenizing Hormone Receptor (keeps estrogen levels high also)
What cells contain the enzyme aromatase to convert androgens to estrogens?
Granulosa cells
What cells produce androgens?
Theca Cells
What causes the increase in temperature during the luteal phase?
Progesterone levels are greater
How does estrogen effect the endometrium?
Estrogen causes thickening and proliferation of the endometrium
Gland develop
Stromal and vessel growth occurs
Uterine lining increases 10 fold
How does progesterone effect the endometrium?
Causes secretion from glands rather than proliferation of glands
When does the placenta become the primary source of progesterone for maintaining the pregnancy?
3-4 months (before that the corpus luteum was the source of progesterone)
Why is the end of the first trimester the interval with the greatest likelihood of miscarriage?
It is the critical transition between uterine dependence on ovarian/corpus luteum vs. placental steroids
Would an oophorectomy at 15 weeks terminate pregnancy?
Nope! At the point the corpus luteum is not necessary for the production of progesterone and estradiol
Describe the hormonal shift that accompanies parturition
Shift from
Progesterone > Estrogen to
Estrogen > Progesterone
How does progesterone effect myometrial cells?
Progesterone hyperpolarizes the myometrial cells which prevent contractions
How does estrodiol prepare the myometrium for delivery?
- Increases oxytocin receptors
- Promotes uterine contractility
- Cervical ripening
- Increases local prostaglandin release from the placenta with causes myometrial contractions
What prostaglandins dominate in reproduction?
PGF2 and PGE2
What are responsible for braxton hicks contractions?
Prostaglandins
What can you give to stop a delivery?
Indomethacin
What does oxytocin do?
Stimulates smooth muscle contraction
What two things induce oxytocin release during parturition?
- Mechanical stimulation of the cervix at end of gestation
- Forceful interine contractions
If no fertilization, what degrades the corpus luteum?
PGF2alpha