Female Reproductive Physiology

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Female Reproductive Physiology - Eggcellent Adventures

  • Folliculogenesis: Maturation journey from primordial follicle → primary → secondary → mature Graafian follicle (~20mm).
  • Two-Cell, Two-Gonadotropin Theory:
    • Theca cells (LH stimulation): Synthesize androgens.
    • Granulosa cells (FSH stimulation): Convert androgens to estrogen via aromatase.
  • Ovulation: LH surge (peaks 24-36h before) triggers release of oocyte.

    ⭐ The LH surge, triggered by sustained high estrogen levels (positive feedback), is essential for ovulation.

  • Luteal Phase:
    • Corpus Luteum: Forms post-ovulation; secretes progesterone (maintains endometrium).
    • Corpus Albicans: Scar tissue if no pregnancy.

Ovarian Folliculogenesis, Ovulation, Corpus Luteum

Female Reproductive Physiology - Monthly Makeover

Uterine cycle (21-35 days); menses 2-7 days. 📌 M-PES (Menstrual, Proliferative-Estrogen, Secretory-Progesterone).

  • Menstrual Phase (Days 1-5):
    • ↓Progesterone → spiral artery spasm, endometrial shedding.
  • Proliferative Phase (Days 6-14, variable):
    • Estrogen-driven: endometrial growth, glands & spiral arteries elongate.
  • Secretory Phase (Days 15-28, fixed ~14 days):
    • Progesterone-dominant: glandular tortuosity & secretion (glycogen, mucus), spiral arteries coil. Decidualization for implantation.
    • No implantation: ↓progesterone → menstruation.

Menstrual Cycle Phases and Hormonal Changes

⭐ The secretory phase endometrium, rich in glycogen and mucus, is prepared by progesterone for potential implantation.

Female Reproductive Physiology - Hormone Harmony

  • Hypothalamus: Secretes GnRH (pulsatile) → stimulates Ant. Pituitary.
  • Ant. Pituitary: Releases FSH (follicle growth) & LH (ovulation/corpus luteum) → act on Ovary.
  • Ovary Hormones & Feedback Loops:
    • Estrogen:
      • Low/Moderate levels: Negative feedback on FSH/LH (↓).
      • Sustained High (pre-ovulatory): Positive feedback → LH surge (↑).
    • Progesterone: Strong negative feedback on GnRH/LH/FSH (↓).
    • Inhibin B (granulosa cells): Negative feedback, selectively ↓FSH.
    • Activin (granulosa cells): Positive feedback, stimulates ↑FSH. Female HPG Axis Diagram

⭐ Inhibin B, produced by granulosa cells under FSH stimulation, selectively inhibits FSH secretion from the anterior pituitary.

Female Reproductive Physiology - Conception & Kick-off

  • Gamete Transport & Fertilization:
    • Sperm: Capacitation & acrosome reaction.
    • Ovum: Picked up by fimbriae.
    • Fertilization site: Ampulla of fallopian tube.

      ⭐ Fertilization typically occurs in the ampulla of the fallopian tube, the widest part of the tube.

  • Early Development: Zygote → Morula → Blastocyst (Inner cell mass & Trophoblast).
  • Implantation (Day 6-10 post-ovulation): Apposition, Adhesion, Invasion.
    • Trophoblast differentiates: Syncytiotrophoblast (produces hCG) & Cytotrophoblast.
  • hCG (Human Chorionic Gonadotropin):
    • Rescues corpus luteum; basis of pregnancy tests.
    • Detectable in serum: 8-11 days post-conception.
    • Doubles every 48-72 hours in early viable intrauterine pregnancy.

Fertilization, blastocyst development, implantation

Female Reproductive Physiology - The Grand Pause

  • Menopause: 12 months amenorrhea post-FMP. Avg. age ~51 (45-55 yrs). Perimenopause is transition.
  • Cause: Ovarian follicle depletion → ↓Estrogen, ↓Inhibin → ↑FSH (diagnostic, >30-40 mIU/mL), ↑LH.
  • Features: Vasomotor (hot flashes), urogenital atrophy, mood/sleep issues, osteoporosis risk.

⭐ Markedly elevated serum FSH levels (e.g., > 30-40 mIU/mL) are a hallmark of menopause due to loss of negative feedback from ovarian estrogen and inhibin.

High‑Yield Points - ⚡ Biggest Takeaways

  • Menstrual cycle is orchestrated by GnRH, FSH, LH, estrogen, and progesterone.
  • Ovulation is triggered by an LH surge, typically around day 14.
  • Corpus luteum produces progesterone to maintain the endometrium.
  • Fertilization usually occurs in the ampulla of the fallopian tube.
  • hCG (human chorionic gonadotropin) maintains the corpus luteum in early pregnancy.
  • Estrogen is responsible for secondary sexual characteristics and endometrial proliferation.
  • Progesterone is the "pregnancy hormone," promoting endometrial secretion and uterine quiescence.

Practice Questions: Female Reproductive Physiology

Test your understanding with these related questions

A middle-aged female presents with increasing visual loss, breast enlargement, and irregular menses. What is the most appropriate investigation to diagnose the underlying condition?

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Flashcards: Female Reproductive Physiology

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The secretions of seminal vesicles are _____

TAP TO REVEAL ANSWER

The secretions of seminal vesicles are _____

alkaline (acidic/alkaline)

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