Reproduction — Set 1

Correct Answer: D. Fallopian tube

• **Fallopian tube** = The Fallopian tube (oviduct) is where the sperm meets and fuses with the egg, forming a zygote; fertilization typically occurs in its ampullary region. • **Key fact** — After fertilization, the zygote travels down the Fallopian tube over 3–4 days before reaching the uterus for implantation. • 💡 Option A (Ovary) is wrong because the ovary releases the egg but fertilization does not happen there; Option B (Uterus) is wrong because the uterus is the site of implantation, not fertilization; Option C (Cervix) is wrong because the cervix is merely the lower opening of the uterus through which sperm enters.

Correct Answer: D. Ovulation

• **Ovulation** = Ovulation is the rupture of a mature Graafian follicle in the ovary that releases a secondary oocyte into the Fallopian tube, triggered by a surge in LH (luteinising hormone). • **Key fact** — Ovulation typically occurs around day 14 of a 28-day menstrual cycle and is the most fertile window for conception. • 💡 Option A (Gestation) is wrong because gestation refers to the entire period of fetal development from conception to birth; Option B (Menstruation) is wrong because menstruation is the shedding of the uterine lining when fertilization does not occur; Option C (Implantation) is wrong because implantation is the embedding of the blastocyst in the uterine wall.

Correct Answer: A. Placenta

• **Placenta** = The placenta is a disc-shaped organ that develops in the uterine wall and acts as the interface between mother and fetus, supplying oxygen and nutrients while removing carbon dioxide and waste via diffusion. • **Key fact** — The placenta also secretes hormones such as hCG, progesterone, and estrogen to sustain the pregnancy. • 💡 Option B (Urethra) is wrong because the urethra is part of the urinary system and has no role in fetal nutrition; Option C (Umbilical cord) is wrong because the umbilical cord is the physical link between fetus and placenta — the placenta itself is the organ that performs exchange; Option D (Amniotic sac) is wrong because the amniotic sac cushions the fetus mechanically but does not deliver nutrients.

Correct Answer: C. 40 weeks

• **40 weeks** = Normal human gestation is approximately 40 weeks (280 days or 9 months) counted from the first day of the last menstrual period, divided into three trimesters of about 13 weeks each. • **Key fact** — A baby born before 37 weeks is considered premature; the critical viability threshold is around 24 weeks. • 💡 Option A (20 weeks) is wrong because 20 weeks marks only mid-pregnancy; Option B (28 weeks) is wrong because 28 weeks is the beginning of the third trimester, not full term; Option D (48 weeks) is wrong because no normal pregnancy lasts 48 weeks — a post-term pregnancy is considered beyond 42 weeks.

Correct Answer: A. Testes

• **Testes** = The testes contain tightly coiled seminiferous tubules where spermatogenesis takes place, producing millions of sperm cells daily; they also produce testosterone. • **Key fact** — The testes are located in the scrotum, outside the body cavity, because sperm production requires a temperature about 2–3°C lower than core body temperature. • 💡 Option B (Vas deferens) is wrong because the vas deferens is merely the duct that carries mature sperm from the epididymis toward the urethra; Option C (Seminal vesicles) is wrong because seminal vesicles secrete fructose-rich fluid that nourishes sperm but do not produce them; Option D (Prostate gland) is wrong because the prostate secretes an alkaline fluid that protects sperm but has no role in sperm production.

Correct Answer: D. Menarche

• **Menarche** = Menarche is the first occurrence of menstruation in a female's life, typically between ages 11–14, signalling the beginning of reproductive maturity. • **Key fact** — Menarche is triggered by rising estrogen levels and marks a key milestone of puberty, but regular ovulatory cycles may take 1–2 years to establish. • 💡 Option A (Lactation) is wrong because lactation refers to milk production in the breasts after childbirth; Option B (Puberty) is wrong because puberty is the broader developmental phase that includes menarche but is not the term specifically for the first period; Option C (Menopause) is wrong because menopause is the permanent cessation of menstruation, the opposite end of the reproductive lifespan.

Correct Answer: D. Uterus

• **Uterus** = The uterus is a thick-walled, pear-shaped muscular organ in the female pelvis whose inner lining (endometrium) thickens each month to receive and nourish a fertilized egg. • **Key fact** — The uterine wall has three layers: perimetrium (outer), myometrium (middle, contracts during labour), and endometrium (inner, shed during menstruation). • 💡 Option A (Vagina) is wrong because the vagina is the birth canal and the organ of copulation, not the site of embryo development; Option B (Oviduct) is wrong because the oviduct (Fallopian tube) transports the egg and is the site of fertilization, not development; Option C (Ureter) is wrong because the ureter is a urinary duct carrying urine from the kidney to the bladder.

Correct Answer: A. hCG

• **hCG** = Human Chorionic Gonadotropin (hCG) is secreted by the trophoblast cells of the implanted embryo from about 6 days after conception and appears in urine, making it the definitive early-pregnancy marker detected by home test strips. • **Key fact** — hCG levels double every 48–72 hours in early pregnancy and peak around weeks 8–10; its detection as early as 10 days post-ovulation makes it the gold standard for pregnancy confirmation. • 💡 Option B (Oxytocin) is wrong because oxytocin triggers labour contractions and milk let-down but is not a pregnancy marker in urine; Option C (Prolactin) is wrong because prolactin stimulates milk production after delivery; Option D (Estrogen) is wrong because estrogen is present throughout the cycle and its level alone cannot confirm pregnancy.

Correct Answer: D. Menopause

• **Menopause** = Menopause is the permanent end of menstruation caused by the depletion of ovarian follicles, typically occurring between ages 45–55, officially confirmed after 12 consecutive months without a period. • **Key fact** — During menopause, estrogen and progesterone levels drop sharply, which can lead to hot flashes, bone loss, and cardiovascular changes. • 💡 Option A (Menstruation) is wrong because menstruation is the monthly shedding of the endometrium, not its cessation; Option B (Ovulation) is wrong because ovulation is the release of an egg, a process that actually stops at menopause; Option C (Menarche) is wrong because menarche is the first menstrual period, the start of reproductive life.

Correct Answer: B. Zona pellucida

• **Zona pellucida** = The zona pellucida is a thick glycoprotein coat surrounding the human oocyte that blocks polyspermy (entry of more than one sperm) and plays a crucial role in species-specific sperm binding during fertilization. • **Key fact** — After fertilization, a cortical reaction hardens the zona pellucida into the fertilization membrane, preventing additional sperm from entering. • 💡 Option A (Cytoplasm) is wrong because cytoplasm is the internal fluid of the cell, not an outer protective layer; Option C (Plasma membrane) is wrong because the plasma membrane lies beneath the zona pellucida and is not the outermost layer; Option D (Nucleus) is wrong because the nucleus is the inner genetic organelle, not a surface structure.