Reproduction — Set 2

Correct Answer: C. Prostate gland

• **Prostate gland** = The prostate gland secretes a milky, slightly alkaline fluid rich in zinc, citric acid, and enzymes that neutralise the acidity of the female reproductive tract, thereby protecting sperm and enhancing their motility. • **Key fact** — Prostate secretions constitute about 25–30% of the total semen volume and contain prostate-specific antigen (PSA), which is used as a cancer marker in clinical tests. • 💡 Option A (Thyroid gland) is wrong because the thyroid produces thyroxine regulating metabolism, not semen components; Option B (Adrenal gland) is wrong because the adrenal gland produces stress hormones like cortisol and adrenaline; Option D (Pituitary gland) is wrong because the pituitary secretes gonadotropins (FSH and LH) to regulate reproduction but does not contribute fluid to semen.

Correct Answer: B. Implantation

• **Implantation** = Implantation is the process by which the blastocyst (6–7 day-old embryo) burrows into and embeds itself in the endometrium of the uterus, typically about 6–10 days after fertilization. • **Key fact** — Successful implantation triggers hCG secretion, which prevents the corpus luteum from degenerating and maintains progesterone production to sustain the pregnancy. • 💡 Option A (Parturition) is wrong because parturition means the act of giving birth; Option C (Ovulation) is wrong because ovulation is the release of the egg from the ovary; Option D (Fertilization) is wrong because fertilization is the fusion of sperm and egg in the Fallopian tube, which precedes implantation.

Correct Answer: D. 23

• **23** = A mature human sperm cell is haploid, containing 23 chromosomes (22 autosomes + 1 sex chromosome — either X or Y), formed by meiosis which halves the chromosome number. • **Key fact** — When a sperm (23 chromosomes) fuses with an egg (23 chromosomes) during fertilization, the resulting zygote has the full diploid complement of 46 chromosomes. • 💡 Option A (44) is wrong because 44 is neither the haploid nor the diploid human chromosome count; Option B (46) is wrong because 46 is the diploid number found in somatic cells, not in gametes; Option C (22) is wrong because 22 represents only the autosomes without the sex chromosome.

Correct Answer: B. Pituitary

• **Pituitary** = The pituitary gland is called the 'Master Gland' because it secretes gonadotropins — Follicle-Stimulating Hormone (FSH) and Luteinising Hormone (LH) — that directly control the gonads' production of sex hormones and gametes. • **Key fact** — The pituitary itself is regulated by the hypothalamus via GnRH (Gonadotropin-Releasing Hormone), making the hypothalamus-pituitary-gonad axis the central hormonal control system for reproduction. • 💡 Option A (Hypothalamus) is wrong because the hypothalamus is the supervisory centre that commands the pituitary but does not directly release sex hormones; Option C (Thyroid) is wrong because the thyroid produces thyroxine and calcitonin, unrelated to direct sex hormone control; Option D (Pancreas) is wrong because the pancreas secretes insulin and glucagon for blood sugar regulation.

Correct Answer: C. Tubectomy

• **Tubectomy** = Tubectomy (female sterilisation) involves cutting, tying, or blocking the Fallopian tubes so that sperm cannot reach the egg, making it a permanent female contraceptive method with over 99% efficacy. • **Key fact** — Tubectomy is a common family-planning surgery under India's national health programmes; the male equivalent is vasectomy, which cuts the vas deferens. • 💡 Option A (Biopsy) is wrong because a biopsy is a diagnostic procedure that removes a small tissue sample for laboratory examination; Option B (Vasectomy) is wrong because vasectomy is male sterilisation that cuts the vas deferens, not the Fallopian tubes; Option D (Hysterectomy) is wrong because hysterectomy is the surgical removal of the entire uterus, a more extensive procedure than tubectomy.

Correct Answer: D. Oxytocin

• **Oxytocin** = Oxytocin, released from the posterior pituitary, is called the 'Birth Hormone' because it triggers rhythmic uterine contractions during labour and creates a positive feedback loop that intensifies contractions until the baby is delivered. • **Key fact** — Synthetic oxytocin (Pitocin) is administered clinically to induce or augment labour; oxytocin also stimulates milk let-down (ejection) during breastfeeding. • 💡 Option A (Prolactin) is wrong because prolactin stimulates milk production in the mammary glands but does not cause uterine contractions; Option B (Vasopressin) is wrong because vasopressin (ADH) regulates water reabsorption in the kidneys, not uterine activity; Option C (Relaxin) is wrong because relaxin loosens pelvic ligaments and the cervix to prepare for delivery but does not cause the active contractions.

Correct Answer: D. Amniotic sac

• **Amniotic sac** = The amniotic sac is a double-layered membrane filled with amniotic fluid that surrounds and cushions the fetus, maintaining a stable temperature, allowing fetal movement, and protecting it from mechanical shocks. • **Key fact** — Amniotic fluid is swallowed and recycled by the fetus, helping mature its lungs and digestive system; 'breaking of waters' refers to the rupture of this sac near the onset of labour. • 💡 Option A (Cervix) is wrong because the cervix is the lower opening of the uterus that dilates during delivery; Option B (Placenta) is wrong because the placenta facilitates nutrient and gas exchange but is not the fluid-filled sac; Option C (Yolk sac) is wrong because the yolk sac is a transient early embryonic structure that provides initial nutrition before the placenta forms.

Correct Answer: D. The cap-like structure on the head

• **The cap-like structure on the head** = The acrosome is a cap-like vesicle covering the anterior portion of the sperm head; it contains hydrolytic enzymes (including hyaluronidase and acrosin) that digest the zona pellucida of the egg, enabling fertilization. • **Key fact** — The acrosome reaction, triggered when sperm contacts the zona pellucida, releases these enzymes in a controlled burst — without it, fertilization cannot occur. • 💡 Option A (The midpiece for energy) is wrong because the midpiece is packed with mitochondria that generate ATP to power the flagellum, not the acrosome; Option B (The nucleus) is wrong because the nucleus is the central part of the sperm head containing the 23 chromosomes; Option C (The tail for movement) is wrong because the tail (flagellum) propels the sperm forward but is entirely separate from the acrosome.

Correct Answer: A. Maintaining the uterine lining

• **Maintaining the uterine lining** = Progesterone, secreted by the corpus luteum after ovulation, maintains and thickens the endometrium (uterine lining) to create a receptive environment for implantation; if no pregnancy occurs, progesterone levels fall and menstruation begins. • **Key fact** — Progesterone also suppresses new ovulation during the luteal phase and, if pregnancy occurs, the placenta takes over progesterone production to sustain the pregnancy throughout gestation. • 💡 Option B (Stimulating ovulation) is wrong because ovulation is triggered by the LH surge, not progesterone; Option C (Developing sperm) is wrong because sperm development is regulated by FSH and testosterone in males; Option D (Producing milk) is wrong because milk production is stimulated by prolactin, secreted from the anterior pituitary.

Correct Answer: A. Colostrum

• **Colostrum** = Colostrum is the thick, yellowish fluid secreted by the mammary glands in the first few days after delivery; it is extremely rich in immunoglobulins (especially IgA), proteins, and vitamins, providing passive immunity to the newborn. • **Key fact** — Colostrum has a laxative effect that helps the newborn expel meconium (first stool) and establishes healthy gut flora; it is sometimes called 'liquid gold' for its protective properties. • 💡 Option B (Casein) is wrong because casein is a major milk protein found in mature milk, not the term for the first secretion; Option C (Serum) is wrong because serum is the liquid component of blood, not a lactation product; Option D (Lactose) is wrong because lactose is the primary sugar in milk, a component of colostrum but not the name for the first milk itself.