Menstrual Cycle

Understand the functions of: Endometrium Follicle vs. Corpus Luteum

Endometrium Inner lining of uterus Blood vessels Preparation for implantation of zygote Eventually forms placenta

Follicle vs. corpus luteum Follicle = pre ovulation (egg present) Protection/nourishment for egg Secretes estrogen Corpus luteum = post ovulation (no egg present) Temporary endocrine gland Secretes progesterone

Follicle vs. corpus luteum Primary oocyte  secondary oocyte  ovulated When does egg complete meiosis II? Follicle  corpus luteum  degenerates (if no baby)

Menstrual Cycle

Roles of Specific Hormones Luteinizing Hormone Preovulation: __________________ Ovulation/Postovulation: ___________________ Follicle Stimulating Hormone Postovulation: ___________________ Progesterone and estrogen are released by the _________________________ following ovulation Estrogen Leads to a spike in _______________, that causes ________________ at Day 14 Progesterone Leads to thickening of the ___________________

Role of Specific Hormones Luteinizing Hormone Preovulation: follicular growth; signals meiosis I to continue occurring Ovulation/Postovulation: follicle bursting (ovulation)… formation of corpus luteum Follicle Stimulating Hormone Preovulation: follicular growth Postovulation: none (except preventing other follicles from developing) Progesterone and estrogen are released by the corpus luteum following ovulation Estrogen Leads to a spike in LH, that causes _ovulation at Day 14 Progesterone Leads to thickening of the endometrium

Confusing Ideas– Estrogen Levels At very low levels, estrogen  increases GnRH  increase FSH and LH Day 1 At low-ish levels, estrogen inhibits FSH and LH Day 2-13ish At high levels, estrogen stimulates LH and FSH (LH surge of ovulation)

Thought Question Why is it important that low-ish levels of estrogen inhibit FSH and LH? HINT: Think about what the roles of FSH and LH are

ANSWER Prevents multiple follicles at multiple stages of development from constantly being produced– otherwise would constantly be concurring ovulating, menstruating, and in follicular and luteal phases with different follicles Dramatic effect on hormones

Confusing Ideas– Estrogen and Progesterone Secretion Estrogen produced by the follicle Progesterone produced by corpus luteum

Hormone Changes After Pregnancy

Pregnancy vs. no pregnancy If no sperm, leads to menstruation If sperm, meiosis II completed in oviduct

Hormone Changes After Pregnancy Corpus luteum  progesterone and estrogen progesterone inhibit LH and FSH Why is inhibition of FSH important? Therefore, human chorionic gonadotrophin (HCG) mimics LH Increased progesterone and estrogen which maintain endometrium

Blood and Urine Tests to Detect Pregnancy Guideline to hCG levels during pregnancy: hCG levels in weeks from LMP (gestational age)* : 3 weeks LMP: 5 - 50 mIU/ml 4 weeks LMP: 5 - 426 mIU/ml 5 weeks LMP: 18 - 7,340 mIU/ml 6 weeks LMP: 1,080 - 56,500 mIU/ml 7 - 8 weeks LMP: 7, 650 - 229,000 mIU/ml 9 - 12 weeks LMP: 25,700 - 288,000 mIU/ml 13 - 16 weeks LMP: 13,300 - 254,000 mIU/ml 17 - 24 weeks LMP: 4,060 - 165,400 mIU/ml 25 - 40 weeks LMP: 3,640 - 117,000 mIU/ml Non-pregnant females: <5.0 mIU/ml

What Must Cause Estrogen and Progesterone Levels to Increase, even with decrease in hCG