---

Important Questions - Reproductive Physiology (1st Year MBBS)

---

MALE REPRODUCTIVE PHYSIOLOGY

1. Spermatogenesis ⭐⭐⭐ (Very Frequently Asked)

• Duration: ~74 days (Guyton) / ~64 days (Costanzo)
• Output: ~120 million sperm produced per day per testis
• Temperature: Requires 35-36°C (1-2°C below body temp) - maintained by countercurrent heat exchange between testicular arteries and veins

• Sertoli cells - support spermatogenesis; form blood-testis barrier via tight junctions; secrete androgen-binding protein (ABP), inhibin, and fluid that transports sperm; secrete estrogens from testosterone (when stimulated by FSH)
• Sertoli cells functions (4): (1) Nutritional support for developing sperm, (2) Form blood-testis barrier, (3) Secrete aqueous fluid for sperm transport, (4) Secrete ABP
• Leydig cells - in interstitium; secrete testosterone when stimulated by LH

1. Testosterone (from Leydig cells) - essential for mitotic division of spermatogonia
2. LH - stimulates Leydig cells to secrete testosterone
3. FSH - stimulates Sertoli cells; essential for spermiogenesis
4. Estrogen (formed from testosterone by Sertoli cells under FSH) - essential for spermiogenesis
5. Growth hormone - promotes early division of spermatogonia; its absence causes infertility

---

2. Structure of the Testis ⭐⭐

• 80% of adult testis = seminiferous tubules (produce sperm)
• 20% = connective tissue + Leydig cells (produce testosterone)
• Blood-testis barrier: tight junctions between Sertoli cells; prevents immune attack on developing sperm

---

3. Testosterone - Synthesis, Transport, and Actions ⭐⭐⭐

---

4. Sperm Maturation and Capacitation ⭐⭐

• Sperm mature in the epididymis (6-meter tube) over ~18-24 hours - gain motility
• Sperm can be stored in epididymis for several weeks while remaining fertile
• Capacitation: After ejaculation, sperm undergo capacitation in the female genital tract - they acquire the ability to fertilize the ovum. Changes in membrane permeability allow calcium influx, enabling the acrosome reaction.
• Acrosome reaction: Release of hyaluronidase and proteolytic enzymes to penetrate the corona radiata and zona pellucida

---

FEMALE REPRODUCTIVE PHYSIOLOGY

5. Oogenesis ⭐⭐⭐

• Gestational week 20-24: ~7 million oogonia (peak)
• Birth: ~2 million primary oocytes (arrested in prophase I)
• Puberty: ~400,000 oocytes
• Menopause: few or none
• Ovulated during reproductive life: only ~400

---

6. Ovarian Cycle and Menstrual Cycle ⭐⭐⭐ (Most Commonly Asked)

OVARIAN CYCLE

• FSH rises → stimulates follicular growth
• Growing follicles secrete increasing estrogen
• Dominant follicle selected; others undergo atresia
• By late follicular phase, estrogen rises sharply

• High estrogen triggers positive feedback on hypothalamus/pituitary
• LH surge (6-10 fold rise, peaks 16 hours before ovulation)
• FSH also rises 2-3 fold
• LH converts granulosa/theca cells to progesterone-secreting cells
• Proteolytic enzymes from lysosomes digest follicle wall
• Prostaglandins cause vasodilation; plasma transudates into follicle
• Stigma ruptures → ovum + corona radiata expelled

• Ruptured follicle forms corpus luteum (granulosa + theca interna cells luteinize)
• Corpus luteum secretes progesterone + estrogen
• This combination causes negative feedback → FSH and LH fall
• If no fertilization: corpus luteum degenerates (luteolysis) at ~day 26
• Progesterone + estrogen fall → FSH/LH rise again → new cycle begins

UTERINE (ENDOMETRIAL) CYCLE

---

7. Preovulatory LH Surge - Mechanism ⭐⭐

• Normally, estrogen exerts negative feedback on anterior pituitary
• But at mid-cycle, when estrogen rises above a critical threshold for 2-3 days, it switches to positive feedback
• This triggers the LH surge (6-8 fold increase) that causes ovulation
• Small amounts of progesterone secreted by granulosa cells just before the surge may also contribute
• Without LH surge, ovulation does not occur

---

8. Corpus Luteum and its Fate ⭐⭐

• Life span: ~12-14 days (if no pregnancy)
• Secretes: progesterone (mainly), estrogen, and inhibin
• If pregnancy occurs: hCG (human chorionic gonadotropin) from trophoblast maintains corpus luteum until placenta takes over (~10-12 weeks)
• hCG has LH-like activity; its detection is the basis of pregnancy tests

---

9. Hormones of Female Reproduction - Summary Table ⭐⭐⭐

---

10. Puberty ⭐⭐

• Girls: Onset 10-14 years (average 12)
• Menarche = first menstruation
• GnRH is present in childhood but suppressed (CNS inhibitory signal missing)
• Kisspeptin receptor gene mutations cause precocious puberty (gain-of-function) or delayed/absent puberty (loss-of-function)

---

11. Fertilization ⭐⭐

• Site: Ampulla of fallopian tube
• Ovum is in secondary oocyte stage at ovulation (meiosis I complete; arrested in meiosis II)
• After sperm penetrates zona pellucida → cortical reaction (prevents polyspermy)
• Meiosis II completes → mature ovum (23 chromosomes) + 2nd polar body expelled
• Male pronucleus (23 chr) + female pronucleus (23 chr) fuse → zygote (46 chromosomes)
• Sperm transport aided by: prostaglandins in semen, oxytocin from female posterior pituitary, uterine contractions
• ~98% of ova successfully enter the fallopian tube

---

12. Menopause ⭐⭐

• Age 40-50 years; cycles become irregular; ovulation fails
• Cause: Ovarian follicles depleted; ovaries no longer respond to FSH/LH
• FSH and LH rise markedly (no negative feedback from estrogen)
• Hot flashes due to instability of hypothalamic thermoregulatory center (estrogen withdrawal)
• Osteoporosis risk increases (estrogen is bone-protective)

---

HIGH-YIELD EXAM POINTS

1. Temperature for spermatogenesis: 35-36°C (1-2°C below body temp)
2. Blood-testis barrier: Tight junctions between Sertoli cells
3. Spermatogenesis duration: ~74 days (Guyton)
4. LH surge: 6-10 fold, peaks 16 hours before ovulation
5. Ovulation day: Day 14 of a 28-day cycle
6. Oocyte stage at ovulation: Secondary oocyte (meiosis I complete)
7. Fertilization site: Ampulla of fallopian tube
8. Corpus luteum maintained by: hCG from trophoblast
9. Inhibin: Specifically suppresses FSH
10. Progesterone raises basal body temperature - used clinically to detect ovulation
11. Primordial follicles at puberty: ~400,000
12. Only ~400 follicles ovulate during entire reproductive life
13. DHT mediates: External genitalia development, prostate, hair pattern (5α-reductase converts testosterone → DHT)
14. Positive feedback: High estrogen at mid-cycle → LH surge → ovulation
15. Negative feedback: Progesterone + estrogen from corpus luteum → suppress FSH/LH in luteal phase

---

LIKELY SHORT ANSWER / ESSAY QUESTIONS

1. Describe the steps of spermatogenesis and the hormonal regulation.
2. Write the phases of the menstrual cycle with hormonal changes.
3. What is the LH surge? How is it triggered and what is its significance?
4. Compare spermatogenesis and oogenesis.
5. Describe the functions of Sertoli cells.
6. Explain the role of FSH and LH in the female reproductive cycle.
7. What is capacitation? Describe the acrosome reaction.
8. Describe the formation and fate of corpus luteum.
9. What are the effects of testosterone? Distinguish from effects of DHT.
10. Describe the hormonal changes at puberty (male or female).
11. What is menopause? Explain the hormonal profile.
12. Describe fertilization - site, stages, and prevention of polyspermy.

---