Human Reproduction is a high-yield chapter because it links basic concepts (menstrual cycle, hormones, fertilization) with clinically important topics (infertility treatments, contraception, ectopic pregnancy, endometriosis, and fetal-maternal hormonal regulation). Board and competitive exams frequently test timing/hormone logic, mechanism-based reasoning, and key clinical correlations—so mastering both physiology and clinical interpretations is essential.
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10
Questions
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Marking
Q1. A woman has a regular 28‑day menstrual cycle with ovulation occurring at noon on day 14. The ovum remains viable for about after ovulation and sperm can survive up to in the female reproductive tract. The couple has intercourse at noon on day 11. Which statement about the possibility and timing of fertilization is correct?
Fertilization is unlikely because sperm viability () is just enough to reach ovulation, so only a small fraction remains viable by day 14 noon.
Fertilization is possible because sperm deposited at noon on day 11 can remain viable until ovulation at noon on day 14; fertilization would then most likely occur within after ovulation.
Fertilization is only possible if ovulation occurs earlier than noon on day 14, since sperm viability declines rapidly and rarely persists the full .
Fertilization is most likely immediately at intercourse on day 11, even before ovulation, because sperm can fertilize an ovum before it is released.
Q2. An ejaculate volume is with sperm concentration . If of sperm are motile at deposition and only of those motile sperm reach the ampullary region of the fallopian tube where fertilization occurs, approximately how many motile sperm arrive at the ampulla?
Q3. A copper intrauterine device (Cu‑IUD) markedly reduces the overall pregnancy rate. However, when pregnancy does occur with an IUD in situ, the relative risk of ectopic (tubal) implantation is increased compared to pregnancies in women without an IUD. Which mechanistic explanation best accounts for this observation?
Cu‑IUDs preferentially increase the likelihood of fertilization within the tube, so fertilized embryos are more often already positioned for ectopic implantation.
Cu‑IUDs increase tubal ciliary beat and transport, so embryos reach tubal sites sooner and ectopic implantation becomes more frequent.
Cu‑IUDs raise systemic progesterone, causing endometrial atrophy that directly drives ectopic implantation.
Cu‑IUDs produce a local inflammatory/endometrial environment and reduce intrauterine implantation; fertilization may still occur, so embryos that cannot implant in the uterus have a higher chance of implanting ectopically.
Q4. A patient with severe endometriosis is started on a continuous (non‑pulsatile) GnRH agonist infusion. Which sequence of changes in , and ovarian steroid secretion is expected during the first week versus after four weeks of continuous therapy?
First week: immediate suppression of and with decreased ovarian steroids; Fourth week: rebound hypersecretion of / and increased steroids.
First week: no significant change in gonadotropins; Fourth week: progressive increase in and causing ovarian stimulation.
First week: transient increase (flare) of and with a rise in ovarian steroids; Fourth week: pituitary GnRH‑receptor down‑regulation causing suppressed / and low estradiol/progesterone.
First week: selective rise in causing follicular growth; Fourth week: persistent luteinization with high progesterone despite low .
Q5. A pregnant woman at 34 weeks’ gestation is treated with indomethacin tocolysis for preterm labour. Which fetal cardiovascular effect is most likely and why?
Increased fetal renal perfusion because inhibition of prostaglandins enhances renal blood flow.
Premature functional closure of the ductus arteriosus due to decreased prostaglandin () synthesis, leading to increased pulmonary vascular resistance and possible fetal pulmonary hypertension.
Persistence of the ductus arteriosus because cyclooxygenase inhibition prevents the constrictive mediator required for ductal closure.
Increased placental perfusion because prostaglandin inhibition causes umbilical vasodilation.
Q6. In a woman with a regular 28‑day cycle, an LH surge is detected on day 13. Ovulation occurs approximately after the LH surge; the ovum remains viable for about and sperm can survive in the female tract up to . Intercourse on which of the following day ranges gives the highest probability of fertilization?
Days 11–14
Days 12–14
Days 12–15
Days 13–16
Q7. In an assisted reproduction cycle a patient is given exogenous to stimulate multiple follicle growth. Immediately before the trigger (which mimics the surge), expression of receptors on theca and granulosa cells is blocked by a drug. Which of the following outcomes is most likely?
Failure of ovulation, reduced estradiol production and failure of luteinization leading to low progesterone
Failure of ovulation but high estradiol and high progesterone due to alone
Normal ovulation but impaired estradiol and progesterone secretion thereafter
Normal ovulation and luteal function because stimulation is sufficient
Q8. The placenta normally converts fetal adrenal DHEA‑S into estrogens (predominantly ) via placental aromatase, while placental is synthesized from maternal cholesterol. If the placenta is congenitally deficient in aromatase but the fetal adrenals produce normal amounts of DHEA‑S, which of the following best describes the expected maternal hormonal/clinical picture and pregnancy outcome?
Markedly decreased maternal , markedly decreased placental and high risk of spontaneous abortion
Normal maternal , decreased placental and virilization of the fetus
Increased maternal , increased and increased risk of preterm labour
Markedly decreased maternal , maternal virilization due to accumulated androgens, normal placental , and pregnancy can be maintained
Q9. A 17‑year‑old individual with karyotype presents with normal breast development, scant pubic/axillary hair, female external genitalia, absence of uterus on ultrasound, and gonads located in the inguinal canals. Which of the following explanations best accounts for these findings?
Testes failed to differentiate so anti‑Müllerian hormone (AMH) was not produced, allowing normal female internal genitalia to develop
Functional caused testicular differentiation with Sertoli cell secretion of AMH (regressing Müllerian ducts), Leydig cell production of testosterone whose peripheral aromatization produced estrogens for breast development, and an androgen receptor defect (androgen insensitivity) prevented masculinization of external genitalia and pubic hair development
Ovaries are present but excessive placental aromatase converted ovarian androgens to estrogens causing feminization despite a male karyotype
Mosaic Turner syndrome produced mixed gonadal tissue explaining female phenotype with retained Y chromosome features
Q10. During capacitation sperm increase intracellular , activate PKA and show increased protein tyrosine phosphorylation, hyperactivated motility and higher acrosome reaction rates. In an IVF lab a sperm sample was accidentally exposed to an inhibitor of soluble adenylate cyclase (thereby blocking rise in ). Which of the following sets of changes in these sperm compared to untreated controls is most likely?
Decreased , decreased protein tyrosine phosphorylation, reduced hyperactivated motility, lower acrosome reaction frequency and decreased fertilization rate
Increased , increased tyrosine phosphorylation and enhanced hyperactivated motility leading to higher fertilization rate
No change in but decreased membrane cholesterol efflux causing failed capacitation despite normal phosphorylation
Decreased but unchanged motility and acrosome reaction because alternative signalling fully compensates