Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 51: At what gestational age do eye movements begin in a fetus?

A. 6 to 9 weeks
B. 11 to 14 weeks
C. 16 to 18 weeks (Correct Answer)
D. 28 to 32 weeks

Explanation: **Explanation:** The development of fetal motor activity follows a specific chronological sequence. Eye movements are a sophisticated neuromuscular function that begins significantly later than basic limb movements. **1. Why 16 to 18 weeks is correct:** Fetal eye movements are first detectable via ultrasonography between **16 and 18 weeks** of gestation. Initially, these are slow, sporadic movements. By 20 weeks, they become more frequent. These early movements are essential for the development of the visual pathways and the extraocular muscles, even though the eyelids remain fused until approximately 24–26 weeks. **2. Analysis of Incorrect Options:** * **6 to 9 weeks:** At this stage, the embryo is just beginning to show spontaneous movements of the trunk and limb buds (around 7–8 weeks). The complex neural circuitry required for coordinated eye movement has not yet developed. * **11 to 14 weeks:** During this period, the fetus exhibits breathing movements, swallowing, and generalized limb movements, but coordinated eye movements are not yet established. * **28 to 32 weeks:** By this stage, eye movements are highly organized. This period marks the transition where **Rapid Eye Movement (REM)** sleep patterns become distinct and recognizable on fetal monitoring. **High-Yield Clinical Pearls for NEET-PG:** * **Eyelid Unfusing:** The eyelids remain fused until about **24–26 weeks**. * **REM Sleep:** Becomes well-established by **30–32 weeks** and is a key indicator of fetal CNS maturity. * **BPP (Biophysical Profile):** Fetal breathing movements (another high-yield milestone) typically start around **10–11 weeks** but are clinically evaluated in the third trimester. * **Quickening:** Maternal perception of fetal movements usually starts at **18–20 weeks** (primigravida) or **16–18 weeks** (multigravida).

Question 52: What is the nongenomic effect of testosterone on vascular smooth muscle?

A. Vasodilation (Correct Answer)
B. Vasoconstriction
C. Increase in prostaglandins
D. Increase in estrogen receptors

Explanation: **Explanation:** The correct answer is **Vasodilation**. **1. Why Vasodilation is Correct:** While testosterone typically acts via genomic pathways (binding to nuclear androgen receptors to alter gene transcription), it also exerts rapid **nongenomic effects** that occur within seconds to minutes. In vascular smooth muscle, testosterone acts as a direct vasodilator. This occurs primarily through: * **Inhibition of L-type voltage-gated calcium channels:** Reducing calcium influx leads to muscle relaxation. * **Activation of Potassium (K+) channels:** This causes hyperpolarization of the smooth muscle cell membrane. * **Nitric Oxide (NO) release:** It can stimulate the vascular endothelium to release NO, further promoting relaxation. **2. Why Other Options are Incorrect:** * **B. Vasoconstriction:** Testosterone generally opposes the vasoconstrictive effects of substances like norepinephrine or endothelin-1 in acute settings. * **C. Increase in prostaglandins:** While some hormones modulate prostaglandins, the primary nongenomic mechanism for testosterone-induced relaxation is ion channel modulation, not a prostaglandin-mediated pathway. * **D. Increase in estrogen receptors:** While testosterone can be aromatized to estrogen (which also causes vasodilation), this is a metabolic conversion rather than a direct "nongenomic effect" of the testosterone molecule itself on vascular resistance. **High-Yield Clinical Pearls for NEET-PG:** * **Rapid Action:** Nongenomic effects are characterized by their **speed** (no protein synthesis required) and are often mediated by second messengers or direct ion channel interaction. * **Gender Neutrality:** This vasodilatory effect is observed in both males and females and in various vascular beds (coronary, mesenteric, and brachial). * **Clinical Significance:** These effects may explain why testosterone replacement therapy sometimes shows cardiovascular benefits, such as improved exercise capacity in men with chronic heart failure.

Question 53: What is the best predictor of ovulation?

A. Estrogen peak
B. Follicle stimulating hormone (FSH) surge
C. Onset of the LH surge (Correct Answer)
D. Preovulatory rise in progesterone

Explanation: **Explanation:** The **onset of the Luteinizing Hormone (LH) surge** is considered the most reliable predictor of ovulation. In a normal menstrual cycle, rising estrogen levels from the dominant follicle exert positive feedback on the anterior pituitary. This triggers a massive release of LH. Ovulation typically occurs **24–36 hours after the onset** of the LH surge and **10–12 hours after the LH peak**. Because the onset occurs earlier and initiates the final maturation of the oocyte, it serves as the most accurate clinical predictor. **Analysis of Incorrect Options:** * **A. Estrogen peak:** While the estrogen peak (occurring ~24–48 hours before ovulation) triggers the LH surge, it is less specific. Estrogen can fluctuate due to multiple follicles, whereas the LH surge is the definitive "go" signal for follicular rupture. * **B. FSH surge:** An FSH surge occurs simultaneously with the LH surge (due to GnRH pulses), but its magnitude is smaller and its role in the actual rupture of the follicle is secondary to LH. * **C. Preovulatory rise in progesterone:** Progesterone begins to rise slightly just before ovulation (secreted by the luteinizing granulosa cells), but this is a consequence of the LH surge, not the primary predictor. **High-Yield NEET-PG Pearls:** * **LH Surge:** Essential for the resumption of Meiosis I (completion of reduction division) and the formation of the first polar body. * **Timing:** Ovulation occurs 14 days *before* the next menses, regardless of cycle length. * **Urine LH Kits:** These kits detect the LH surge to identify the "fertile window." * **Mittelschmerz:** Pelvic pain associated with ovulation, often due to peritoneal irritation by follicular fluid/blood.

Question 54: Luteinizing hormone (LH) acts on which of the following cells, except?

A. Interstitial cells
B. Granulosa cells (Correct Answer)
C. Luteal cells
D. Thecal cells

Explanation: The action of Luteinizing Hormone (LH) is mediated by LH receptors located on specific target cells. The correct answer is **Granulosa cells** because, in a typical menstrual cycle, these cells primarily express **FSH receptors**, not LH receptors (until the late follicular phase/pre-ovulatory surge). ### **Detailed Explanation** 1. **Granulosa Cells (Correct Answer):** During the follicular phase, FSH stimulates granulosa cells to convert androgens into estrogens via the enzyme *aromatase*. While granulosa cells do acquire LH receptors just before ovulation (to respond to the LH surge), they are classically considered the primary target for **FSH**, making them the "exception" in this list of primary LH targets. 2. **Interstitial Cells (Incorrect):** Also known as **Leydig cells** in the testes, these possess LH receptors. LH stimulation here is essential for the production of testosterone. 3. **Thecal Cells (Incorrect):** Located in the ovarian follicle, theca interna cells have LH receptors. LH stimulates them to produce androgens (androstenedione), which then diffuse to granulosa cells for estrogen synthesis (the **Two-Cell, Two-Gonadotropin Theory**). 4. **Luteal Cells (Incorrect):** After ovulation, the ruptured follicle becomes the corpus luteum. Both theca-lutein and granulosa-lutein cells express LH receptors, as LH (and later hCG) is required to maintain the corpus luteum and stimulate progesterone production. ### **High-Yield NEET-PG Pearls** * **Two-Cell, Two-Gonadotropin Theory:** LH acts on **Theca cells** (produces Androgens); FSH acts on **Granulosa cells** (converts Androgens to Estrogens). * **LH Surge:** Triggered by a positive feedback loop of Estrogen (>200 pg/mL for >48 hours). It is responsible for ovulation and the completion of Meiosis I. * **Mnemonic:** **L**H acts on **L**eydig cells; **F**SH acts on **S**ertoli cells (in males).

Question 55: Which cells produce Anti-Mullerian hormone in females?

A. Corpus luteum
B. Theca cells
C. Granulosa cells (Correct Answer)
D. Corona radiata

Explanation: **Explanation:** **Anti-Müllerian Hormone (AMH)**, also known as Müllerian Inhibiting Substance, is a glycoprotein belonging to the TGF-β superfamily. In females, it is produced exclusively by the **Granulosa cells** of pre-antral and small antral follicles in the ovary. 1. **Why Granulosa Cells are correct:** AMH production begins in the granulosa cells of primary follicles once they recruit from the primordial pool. Production peaks during the pre-antral and small antral stages (follicles <8mm) and ceases once the follicle reaches the dominant stage or undergoes atresia. Because it is produced by the growing follicle pool, it serves as a direct marker of the **ovarian reserve**. 2. **Why other options are incorrect:** * **Corpus luteum:** This structure is formed after ovulation and primarily secretes progesterone and inhibin A; it does not produce AMH. * **Theca cells:** These are the outer layer of the follicle responsible for androgen production (under LH stimulation) but do not synthesize AMH. * **Corona radiata:** These are specialized granulosa cells surrounding the oocyte at ovulation; while they are derived from granulosa cells, the bulk of AMH production occurs in the earlier, smaller follicular stages. **High-Yield Clinical Pearls for NEET-PG:** * **Ovarian Reserve Marker:** AMH is the most sensitive biochemical marker for ovarian reserve as its levels are relatively constant throughout the menstrual cycle (unlike FSH). * **PCOS:** AMH levels are significantly **elevated** in Polycystic Ovary Syndrome due to the high number of small antral follicles. * **Male Development:** In males, AMH is secreted by **Sertoli cells** and causes the regression of Müllerian ducts (precursors to the uterus and fallopian tubes). * **Tumor Marker:** AMH is used as a tumor marker for **Granulosa cell tumors** of the ovary.

Question 56: In a 29-day menstrual cycle, at which day does ovulation typically occur?

A. 14th day
B. 15th day (Correct Answer)
C. 16th day
D. 17th day

Explanation: ### Explanation The key to determining the day of ovulation lies in understanding the phases of the menstrual cycle. The cycle is divided into the **Follicular phase** (variable in length) and the **Luteal phase** (constant in length). **1. Why Option B (15th day) is correct:** The **Luteal phase** is physiologically fixed at **14 days** because it represents the functional lifespan of the *Corpus Luteum*. To calculate the day of ovulation, one must subtract the fixed luteal phase from the total cycle length: * **Formula:** Day of Ovulation = Total Cycle Length – 14 days * **Calculation:** 29 – 14 = **Day 15** **2. Why other options are incorrect:** * **Option A (14th day):** This is the ovulation day for a standard **28-day cycle** (28 – 14 = 14). It is a common mistake to assume ovulation always occurs on day 14 regardless of cycle length. * **Options C & D (16th & 17th days):** These would be the ovulation days for cycles lasting 30 and 31 days, respectively. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **LH Surge:** Ovulation occurs **10–12 hours after the LH peak** and **32–36 hours after the initial rise** in LH levels. * **Mittelschmerz Syndrome:** Pelvic pain experienced mid-cycle due to peritoneal irritation by follicular fluid/blood released during ovulation. * **Fern Test:** Disappears after ovulation due to the influence of **Progesterone**, which makes cervical mucus thick and cellular. * **Basal Body Temperature (BBT):** Increases by 0.5–1.0°F after ovulation due to the thermogenic effect of Progesterone.

Question 57: Which of these is the function of Decidua basalis of the endometrium?

A. Monthly proliferation in response to estrogen
B. Formation of placenta (Correct Answer)
C. Shedding during menstrual phase
D. Secretory changes in response to progesterone

Explanation: **Explanation:** The **Decidua** is the modified functional layer of the endometrium during pregnancy, transformed under the influence of progesterone (decidualization). It is divided into three distinct regions based on its anatomical relationship to the implanted embryo: 1. **Decidua Basalis (Correct Answer):** This is the part of the decidua located directly deep to the conceptus (at the site of implantation). It interacts with the fetal chorion frondosum to form the **maternal component of the placenta**. It provides the vascular environment necessary for nutrient and gas exchange. 2. **Decidua Capsularis:** The portion that covers the blastocyst, separating it from the uterine cavity. 3. **Decidua Parietalis:** The remainder of the endometrium lining the rest of the uterine cavity. **Analysis of Incorrect Options:** * **Options A & D:** These describe the cyclical changes of the **functional layer** of the endometrium during a non-pregnant menstrual cycle (Proliferative phase under Estrogen and Secretory phase under Progesterone). Once pregnancy occurs, these changes transition into decidualization. * **Option C:** Shedding during the menstrual phase involves the *Stratum Functionale*. In pregnancy, the decidua is maintained to support the fetus and is only shed after parturition (childbirth). **High-Yield NEET-PG Pearls:** * **Nitabuch’s Layer:** A fibrinoid layer between the decidua basalis and the cytotrophoblast that prevents over-invasion of the placenta. Absence of this layer leads to **Placenta Accreta**. * **Arias-Stella Reaction:** Hypersecretory changes in endometrial glands (enlarged nuclei) seen in pregnancy; it can be mistaken for malignancy but is a normal response to HCG. * The **Chorion Frondosum** (fetal part) + **Decidua Basalis** (maternal part) = **The Placenta**.

Question 58: What is characteristic of female oogenesis?

A. Meiosis initiated once in a finite population of cells
B. One gamete produced per meiosis
C. Completion of meiosis delayed for months or years
D. All of the above (Correct Answer)

Explanation: **Explanation:** Oogenesis is the complex process of female gamete formation, characterized by several unique features that distinguish it from spermatogenesis. * **Option A (Meiosis initiated in a finite population):** Unlike males, who have stem cells (spermatogonia) that divide throughout life, females are born with a fixed number of primary oocytes. No new oocytes are formed after birth. Meiosis begins during fetal life (around the 5th month of gestation) for this entire finite population. * **Option B (One gamete per meiosis):** In oogenesis, meiotic divisions are asymmetrical. Each primary oocyte undergoes meiosis to produce only **one functional ovum** and two or three non-functional **polar bodies**. This ensures that the single ovum retains the bulk of the cytoplasm and nutrients required for early embryonic development. * **Option C (Delayed completion):** Meiosis in females involves two significant arrests. It starts in utero but halts in **Prophase I (Dictyotene stage)** until puberty. After ovulation, it halts again in **Metaphase II** and is only completed if fertilization occurs. This delay can span from 12 to 50 years. Since all three statements accurately describe the physiological process, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **First Arrest:** Prophase I (Dictyotene stage) – mediated by Oocyte Maturation Inhibitor (OMI). * **Second Arrest:** Metaphase II – triggered by MPF (Maturation Promoting Factor) and released only by sperm entry. * **Maximum Oocytes:** At 20 weeks of gestation (~7 million); at birth (~1-2 million); at puberty (~300,000-400,000). * **Non-disjunction:** The long duration of the meiotic arrest (Option C) is the primary reason for the increased risk of chromosomal abnormalities (like Down Syndrome) in children of older mothers.

Question 59: All of the following are indicators of ovulation except?

A. Increase in cervical mucus
B. Abdominal cramps
C. LH surge
D. Fall in body temperature (Correct Answer)

Explanation: **Explanation:** The correct answer is **D (Fall in body temperature)** because ovulation is actually associated with a **rise** in Basal Body Temperature (BBT). 1. **Why Option D is correct:** Under the influence of **Progesterone** secreted by the corpus luteum after ovulation, the hypothalamic thermoregulatory center is affected, leading to a rise in BBT by approximately **0.5°F to 1.0°F (0.3°C to 0.5°C)**. This rise persists until the next menses. A "fall" in temperature is not a sustained indicator of the post-ovulatory phase. 2. **Why other options are incorrect:** * **Increase in cervical mucus:** High estrogen levels just before ovulation make the cervical mucus profuse, watery, clear, and stretchable (**Spinnbarkeit effect**), facilitating sperm transport. * **Abdominal cramps:** Known as **Mittelschmerz** (middle pain), this is a common clinical sign of ovulation caused by peritoneal irritation from follicular fluid or blood released during rupture. * **LH surge:** This is the most reliable predictor of impending ovulation. The surge occurs 24–36 hours before the egg is released and is triggered by the positive feedback of Estrogen. **Clinical Pearls for NEET-PG:** * **Fern Test:** Estrogen causes a "ferning" pattern in cervical mucus due to high NaCl content; this disappears after ovulation due to Progesterone. * **Most accurate timing:** Ovulation occurs **14 days prior** to the next menstrual period (constant luteal phase). * **LH Surge Timing:** Ovulation occurs 10–12 hours after the LH **peak** and 32–36 hours after the **onset** of the LH surge.

Question 60: What is the strongest stimulus of lactation?

A. Metoclopramide
B. Postpartum hemorrhage
C. Bromocriptine
D. Suckling (Correct Answer)

Explanation: **Explanation:** The correct answer is **Suckling (Option D)**. **Why Suckling is the strongest stimulus:** Lactation is governed by a neuroendocrine reflex known as the **Milk Ejection Reflex (Ferguson reflex/Let-down reflex)**. When an infant suckles, sensory receptors in the nipple send afferent impulses to the hypothalamus. This triggers two distinct pathways: 1. **Prolactin Release:** Inhibition of Dopamine (Prolactin Inhibiting Hormone) leads to increased Prolactin secretion from the anterior pituitary, which stimulates **milk production**. 2. **Oxytocin Release:** Stimulation of the posterior pituitary leads to Oxytocin release, causing contraction of myoepithelial cells in the mammary glands, resulting in **milk ejection**. Suckling is the physiological "gold standard" stimulus that maintains both production and let-down. **Analysis of Incorrect Options:** * **A. Metoclopramide:** This is a dopamine antagonist. By blocking dopamine, it increases prolactin levels and can be used as a *galactagogue*, but it is a pharmacological intervention, not the primary physiological stimulus. * **B. Postpartum Hemorrhage (PPH):** Severe PPH can lead to **Sheehan’s Syndrome** (pituitary necrosis), which actually causes a *failure* of lactation due to the loss of prolactin-secreting cells. * **C. Bromocriptine:** This is a dopamine agonist. It inhibits prolactin secretion and is clinically used to **suppress** lactation (e.g., after stillbirth). **High-Yield Clinical Pearls for NEET-PG:** * **Prolactin** = Milk Production (Synthesis). * **Oxytocin** = Milk Ejection (Let-down). * **Lactational Amenorrhea:** High prolactin levels during suckling inhibit GnRH pulse frequency, suppressing the LH surge and preventing ovulation. * **PIH (Prolactin Inhibiting Hormone):** Now confirmed to be **Dopamine**.

Practice by Chapter

Male Reproductive Physiology

Practice Questions

Spermatogenesis and Sperm Function

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Female Reproductive Physiology

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Menstrual Cycle

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Ovulation and Fertilization

Practice Questions

Physiology of Pregnancy

Practice Questions

Parturition

Practice Questions

Lactation

Practice Questions

Sexual Differentiation and Development

Practice Questions

Reproductive Aging

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