MBBS 1st Prof Physiology - Female Reproductive System: Must-Study Topics for Proff

🔴 SURE-SHOT LONG QUESTIONS (Most Repeated)

1. Menstrual Cycle (THE most important topic)

• Definition - 28-day cycle, starting from day 1 of menstruation
• Phases of the Ovarian Cycle:
  • Follicular phase (days 1-13): Primordial follicles → dominant Graafian follicle develops; granulosa cells secrete estrogen (by aromatizing androgens from theca interna cells)
  • Ovulation (day 14): Triggered by the LH surge; follicle ruptures ~9 hours after LH peak; ovum picked up by fimbriae
  • Luteal phase (days 15-28): Corpus luteum forms (from granulosa + theca cells), secretes estrogen + progesterone; if no fertilization → corpus luteum degenerates → menstruation
• Phases of the Endometrial (Uterine) Cycle:
  • Menstrual phase (days 1-5): Endometrium sheds
  • Proliferative phase (days 6-13): Estrogen causes endometrial thickening
  • Secretory phase (days 15-28): Progesterone causes glandular secretion, prepares for implantation
• Correlate ovarian changes with endometrial changes - examiners love this correlation
• Draw the graph of FSH, LH, estrogen, progesterone across 28 days (this diagram is high yield)

Source: Ganong's Review of Medical Physiology, 26th Edition, Ch. 22

2. Hormonal Regulation of Menstrual Cycle

• Hypothalamus: GnRH (pulsatile) → stimulates anterior pituitary
• Anterior Pituitary: FSH + LH
• FSH → follicle development → estrogen production
• Early follicular phase: Low estrogen = negative feedback on LH/FSH
• Pre-ovulatory: High estrogen (>200 pg/mL for >36h) = positive feedback → LH surge → ovulation
• Luteal phase: Estrogen + progesterone = negative feedback → FSH/LH fall → corpus luteum regresses → menstruation
• This feedback switch (negative → positive → negative) is a favorite short and long question

3. Actions of Estrogen

4. Actions of Progesterone

🟠 HIGH-YIELD SHORT QUESTIONS (2-4 marks, very frequently asked)

5. LH Surge

• Triggered by high estrogen (positive feedback)
• Occurs at day 13-14
• Causes: ovulation (follicle rupture), luteinization of granulosa cells, synthesis of progesterone, increases prostaglandins
• Ovulation occurs ~9h after LH peak (or ~36-48h after surge begins)

6. Corpus Luteum

• Forms from granulosa + theca cells after ovulation
• Secretes: progesterone (mainly) + estrogen
• Lifespan: 14 days if no fertilization → degenerates (luteolysis) due to falling LH
• If pregnancy: hCG from trophoblast maintains corpus luteum until placenta takes over (8-10 weeks)

7. Indicators/Tests of Ovulation

• Basal body temperature (BBT): Rises 0.5°C after ovulation (due to progesterone thermogenic effect)
• Cervical mucus: Pre-ovulation = thin, watery, shows ferning; post-ovulation = thick (progesterone effect)
• Mittelschmerz: Mid-cycle pain due to follicular fluid irritating peritoneum
• LH surge detection: Urine LH test kits
• Ultrasound: Follicle tracking
• Serum progesterone on day 21: >5 ng/mL confirms ovulation

8. Human Chorionic Gonadotropin (hCG)

• Produced by: syncytiotrophoblast of placenta
• Structure: similar to LH (shares alpha subunit)
• Function: maintains corpus luteum in early pregnancy → maintains progesterone → prevents menstruation
• Basis of all pregnancy tests (detectable from day 8-9 post-fertilization)
• Peak: 8-10 weeks of pregnancy, then falls as placenta takes over progesterone production

9. Placental Hormones / Functions of Placenta

• hCG (maintains corpus luteum)
• Human Placental Lactogen (hPL): Insulin antagonist, promotes fetal nutrition, mammary gland preparation
• Estrogen (mainly estriol - fetoplacental unit)
• Progesterone (takes over from corpus luteum at 8-10 wk)
• CRH, GnRH (produced locally)

10. Menarche & Puberty

• Menarche = first menstrual period; average age 12-13 years
• Sequence of puberty in females (mnemonic "TELARCHE"):
  1. Thelarche (breast budding) - first sign
  2. Adrenarche (pubic/axillary hair)
  3. Growth spurt
  4. Menarche (last)
• Trigger: GnRH pulsatility resumes after childhood quiescence

11. Menopause

• Definition: cessation of menstruation for 12 months; average age 51 years
• Cause: ovarian follicle exhaustion → estrogen falls → negative feedback lost → FSH + LH rise markedly
• Features: hot flushes, osteoporosis, vaginal atrophy, cardiovascular risk increases
• Diagnosis: FSH > 40 mIU/mL

12. Oral Contraceptives

• Combined OCP: estrogen + progestin
• Mechanisms: suppress LH surge (prevents ovulation), thick cervical mucus (blocks sperm), thin atrophic endometrium (prevents implantation)
• Progestin-only pill: mainly cervical mucus + endometrial effects; no consistent ovulation suppression

13. Oogenesis

• Begins in fetal life; primary oocytes arrested in prophase I until puberty
• At ovulation: completes meiosis I → secondary oocyte (arrested in metaphase II)
• Meiosis II completes only at fertilization
• Total oocytes: 2 million at birth → 400,000 at puberty → ~400 ovulated in lifetime

🟡 ADDITIONAL SHORT NOTES (Prepare briefly)

• Fetoplacental unit - estriol synthesis requires fetal DHEA-S → placenta aromatizes to estriol; shows both fetal and placental health
• Prolactin - secreted by anterior pituitary; stimulates milk production; high prolactin inhibits GnRH (explains lactational amenorrhea)
• Oxytocin - from posterior pituitary; causes uterine contractions (labor) + milk ejection (let-down reflex); Ferguson reflex
• Cyclical changes in breasts - estrogen: duct proliferation; progesterone: lobular/alveolar growth
• BBT chart - how to use and interpret
• IUCD mechanism - creates hostile environment in uterus; Cu-IUCDs are spermicidal; hormonal IUDs release progestin

Study Strategy

1. Draw the menstrual cycle diagram (hormones + endometrial changes together) at least 3-4 times until you can reproduce it from memory
2. Compare estrogen vs progesterone actions as a table - common short question
3. Link each topic - e.g., LH surge → ovulation → corpus luteum → progesterone → BBT rise → thick mucus - all connected
4. Guyton & Hall Chapter 82 and Ganong Chapter 22 are the best references for this section
5. From the exam data, the menstrual cycle long question appears in virtually every university exam - do NOT skip it