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Chapter 17

Chapter 17. Female Reproduction. The Female Reproductive System Produces Eggs and Nurtures the Embryo and Fetus. Female Reproductive System. Ovaries: release oocytes and secrete the hormones estrogen and progesterone Oviduct (a.k.a., Fallopian Tube) After ovulation eggs enter oviduct

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Chapter 17

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  1. Chapter 17 Female Reproduction

  2. The Female Reproductive System Produces Eggs and Nurtures the Embryo and Fetus

  3. Female Reproductive System • Ovaries: release oocytes and secrete the hormones estrogen and progesterone • Oviduct (a.k.a., Fallopian Tube) • After ovulation eggs enter oviduct • Site where fertilization occurs • Site of ectopic pregnancy

  4. Female Reproductive System • Uterus: the organ where fertilized egg grows and develops • Layers • Endometrium: supports fertilized egg, sloughs off during menstrual flow • Endometriosis: ectopic growth outside uterus • Myometrium: Thick muscular layer, expands during pregnancy & responsible for labor contractions during childbirth • Cervix: the narrow opening in the lower part of the uterus that permits sperm to enter the uterus

  5. True / False • Fertilization normally takes place in the uterus.

  6. True / False • Implantation of the embryo normally occurs in the oviduct.

  7. The Ovarian Cycle • Purpose: • Egg production and ovulation

  8. Mature (Graafian) Follicle

  9. The Menstrual Cycle • The ovarian and uterine cycles are coordinated by hormones • Estrogen, Progesterone • Luteinizing Hormone (LH) • Follicle Stimulating Hormone (FSH)

  10. Menstrual Cycle: Ovarian Cycle • Ovarian Cycle: oocytes mature and are released • Follicle develops under the influence of FSH • Follicle produces increasing estrogen • (Graafian) Follicle matures & produces lots of estrogen • Increasing estrogen causes surge of LH (positive fdbk) which induces ovulation • Corpus luteum (CL) formed from follicle, large amounts of progesterone secreted • CL degenerates and progesterone declines

  11. Ovarian follicles • Are stimulated to develop by FSH • Contain a single egg • Secrete estrogen • Release an egg during ovulation

  12. Menstrual Cycle: Uterine Cycle • Uterine cycle: prepares uterus for pregnancy • Menstrual phase (days 1-5): Progesterone levels decline → endometrial lining degenerates → menstruation occurs • Proliferative (follicular) phase (days 6-14): Estrogen increases → causes endometrial lining to proliferate • Ovulation (day 14): Induced by high estrogen & LH • Luteal phase: Corpus luteum produces progesterone (and estrogen) → endometrium proliferates further to prepare for implantation

  13. Hormonal Control of Endometrium & Menstrual Bleeding

  14. The Corpus Luteum • Develops from the ovarian follicle after ovulation • Secretes progesterone and estrogen • Prepares the uterine endometrium for embryo implantation

  15. Maintenance of Menstrual Cycle • Positive and negative feedback of steroid hormones on the pituitary • Positive feedback • At the end of follicular growth phase, increasing (i.e., very high) estrogen levels cause surge in LH • Negative feedback • In both follicular and luteal phases, steady (but lower) levels of estrogen and progesterone inhibit LH and FSH release

  16. Figure 16.8

  17. Mammalian Egg with Sperm Human Egg with Sperm Zona Pellucida

  18. Pregnancy

  19. What if the uterus becomes pregnant? • Sloughing of endometrium would be disastrous for a newly implanted embryo • Constant supply of progesterone from corpus luteum (CL) is necessary to maintain endometrium

  20. hCG Saves the Embryo • Newly implanted embryo secretes hCG (human chorionic gonadotropin) which prolongs the lifespan of CL • CL continues to secrete progesterone which maintains endometrium (and hence fetus)

  21. hCG is the basis of pregnancy test • hCG is specific (unique) to pregnancy • The presence of hCG in blood or urine is the basis of a positive test for pregnancy.

  22. The protein hormone that rescues the CL and is the basis of the pregnancy test • Relaxin • hCG • Estrogen • FSH

  23. Menopause ends a woman’s reproductive ability • Main Hypothesis • Ovaries become depleted of eggs

  24. Infertility: Inability to Conceive • Many causes of infertility • Number and quality of sperm, pelvic inflammatory disease (PID), endometriosis • Enhancing fertility • Options: artificial insemination, in vitro fertilization, GIFT and ZIFT, fertility enhancing drugs, surrogate mothers

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