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– Preovulation: __________________– 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/ml4 weeks LMP: 5 - 426 mIU/ml5 weeks LMP: 18 - 7,340 mIU/ml6 weeks LMP: 1,080 - 56,500 mIU/ml7 - 8 weeks LMP: 7, 650 - 229,000 mIU/ml9 - 12 weeks LMP: 25,700 - 288,000 mIU/ml13 - 16 weeks LMP: 13,300 - 254,000 mIU/ml17 - 24 weeks LMP: 4,060 - 165,400 mIU/ml25 - 40 weeks LMP: 3,640 - 117,000 mIU/mlNon-pregnant females: <5.0 mIU/ml

What Must Cause Estrogen and Progesterone Levels to Increase, even

with decrease in hCG