Female Reproduction

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Chapter 17

• Female Reproduction

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

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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

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The Ovarian Cycle

• Involves egg production and ovulation

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Mature (Graafian) Follicle
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The Menstrual Cycle

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

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Menstrual Cycle Ovarian Cycle

• Ovarian Cycle oocytes mature and are released
• Follicle develops under the influence of FSH
• Follicle produces increasing estrogen
• Follicle matures (Graafian follicle) 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

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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

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Hormonal Control of Endometrium Menstrual
Bleeding
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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

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Figure 16.8
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Mammalian Egg with Sperm
Human Egg with Sperm
Zona Pellucida
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Menopause ends a womans reproductive ability

• Two hypotheses
• Ovaries become depleted of eggs
• Aging hypothalamus secretes less GnRH ? less LH
  and FSH secretion from pituitary

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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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