Reproductive Physiology Practice Questions

Q: What is the best predictor of ovulation?

Onset of the LH surge. **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.

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

Granulosa cells. 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).

Q: Which cells produce Anti-Mullerian hormone in females?

Granulosa cells. **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.

Q: What is characteristic of female oogenesis?

All of the above. **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.

Q: All of the following are indicators of ovulation except?

Fall in body temperature. **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.

Q: What is the strongest stimulus of lactation?

Suckling. **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**.

Q: What is the two-gonadotropin hypothesis?

FSH acts on granulosa cells and LH acts on theca cells.. The **Two-Cell, Two-Gonadotropin Hypothesis** describes the synergistic relationship between theca and granulosa cells in the ovarian follicle to produce estradiol. ### Why Option B is Correct The production of estrogen requires two distinct cell types and two different gonadotropins: 1. **Theca Cells (LH):** LH stimulates theca cells to convert cholesterol into **androgens** (androstenedione and testosterone). Theca cells lack the enzyme *aromatase*, so they cannot produce estrogen themselves. 2. **Granulosa Cells (FSH):** FSH stimulates granulosa cells to take up the androgens produced by theca cells. Under the influence of FSH, the enzyme **aromatase** converts these androgens into **estradiol**. Granulosa cells lack the enzymes necessary to synthesize androgens from cholesterol, making them dependent on theca cells. ### Why Other Options are Incorrect * **Option A:** FSH and LH *stimulate* (rather than inhibit) the synthesis of estrogen and progesterone. * **Option C:** Both FSH and LH are essential for estrogen production; LH provides the precursor (androgen), and FSH facilitates the final conversion. * **Option D:** Estrogen and progesterone provide feedback to the hypothalamus and pituitary; the gonadotropins themselves are the effectors, not the primary feedback signals in this context. ### High-Yield NEET-PG Pearls * **Mnemonic:** **L**H acts on **L**evel 1 (Theca - outer) to make androgens; **F**SH acts on **F**actory (Granulosa - inner) to finish the product. * **Enzyme Key:** Theca cells have **17α-hydroxylase** (needed for androgens); Granulosa cells have **Aromatase** (needed for estrogens). * **Clinical Correlation:** In PCOS, an elevated LH:FSH ratio leads to excess androgen production by theca cells, which cannot be fully converted to estrogen, resulting in hyperandrogenism.

Q: According to the World Health Organization 2010 strict criteria for semen analysis morphology, what percentage of normal forms is considered indicative?

>=4% normal forms. ### Explanation The correct answer is **B. >=4% normal forms**. This question tests knowledge of the **WHO Laboratory Manual for the Examination and Processing of Human Semen (5th Edition, 2010)**, which introduced the "Kruger’s Strict Criteria" for assessing sperm morphology. #### Why Option B is Correct: Under the 2010 WHO criteria, the lower reference limit for **normal forms is 4%** (5th percentile). This "strict" assessment requires the sperm to have a perfectly smooth, oval head, a well-defined acrosome (occupying 40–70% of the head), and no neck, midpiece, or tail defects. Even minor irregularities classify the sperm as "abnormal." #### Why Other Options are Incorrect: * **Option A (>15%):** This was the cutoff used in the **1992 (3rd Edition)** WHO criteria. It is now considered outdated. * **Option C (>=25%):** This value does not correspond to any standard WHO threshold for morphology. * **Option D (>=32%):** This is the WHO 2010 lower reference limit for **Progressive Motility (PR)**, not morphology. #### High-Yield Clinical Pearls for NEET-PG: To master semen analysis questions, remember these **WHO 2010 Reference Values**: 1. **Volume:** ≥1.5 mL 2. **Total Sperm Count:** ≥39 million per ejaculate 3. **Sperm Concentration:** ≥15 million/mL 4. **Total Motility (PR + NP):** ≥40% 5. **Progressive Motility (PR):** ≥32% 6. **Vitality (Live Sperm):** ≥58% 7. **Morphology:** ≥4% normal forms **Note:** The 6th Edition (2021) maintains the 4% morphology threshold but has slightly updated other parameters (e.g., volume to 1.4 mL); however, the 2010 criteria remain the most frequently tested in exams.

Q: Resolution of corpus luteum occurs because of:

Decreased levels of LH. **Explanation:** The **corpus luteum (CL)** is a temporary endocrine structure formed from the empty follicle after ovulation. Its primary function is to secrete high levels of progesterone and moderate levels of estrogen to prepare the endometrium for implantation. **Why Option C is Correct:** The survival and maintenance of the corpus luteum are strictly dependent on **Luteinizing Hormone (LH)**. LH provides the necessary "luteotropic" support. After ovulation, if fertilization does not occur, the high levels of progesterone and estrogen exert **negative feedback** on the anterior pituitary, leading to a significant **decrease in LH secretion**. Without the trophic support of LH, the corpus luteum cannot sustain itself, leading to its involution (luteolysis) and subsequent transformation into the fibrous *corpus albicans*. **Why Other Options are Incorrect:** * **Options A & B:** Increased levels of progesterone and estrogen are the *products* of the corpus luteum, not the cause of its resolution. While they indirectly cause resolution via negative feedback on LH, the direct physiological trigger for luteolysis is the withdrawal of LH support. * **Option D:** While FSH levels also decline during the luteal phase due to inhibin and steroid feedback, FSH is primarily responsible for follicular recruitment and growth, not the maintenance of the corpus luteum. **High-Yield NEET-PG Pearls:** * **Rescue of Corpus Luteum:** If pregnancy occurs, the syncytiotrophoblast secretes **hCG (human Chorionic Gonadotropin)**. hCG is structurally similar to LH and binds to LH receptors, "rescuing" the corpus luteum from degradation until the placenta takes over progesterone production (the luteal-placental shift at ~7–9 weeks). * **Luteolysis Trigger:** In humans, luteolysis is primarily an intra-ovarian process triggered by LH withdrawal, unlike in many mammals where uterine Prostaglandin F2α (PGF2α) is the primary luteolytic agent.

Q: What type of cell division is responsible for the early phase division of spermatogonia?

Mitosis. **Explanation:** The correct answer is **Mitosis**. **Why Mitosis is correct:** Spermatogenesis begins with **spermatogonia** (diploid stem cells, 46 XY) located on the basement membrane of the seminiferous tubules. In the early phase, these cells undergo **mitotic division** to serve two purposes: 1. **Self-renewal:** Maintaining the stem cell population (Type A spermatogonia). 2. **Proliferation:** Producing cells destined to become sperm (Type B spermatogonia). Since the goal of this stage is to increase the cell count while maintaining a full diploid complement of chromosomes, mitosis is the required mechanism. **Why other options are incorrect:** * **Meiosis:** This occurs later in the process. Only **Primary Spermatocytes** undergo Meiosis I (to become secondary spermatocytes) and Meiosis II (to become spermatids) to achieve haploidy (23 chromosomes). * **Both Meiosis and Mitosis:** While both occur during the *entire* process of spermatogenesis, the question specifically asks for the **early phase division of spermatogonia**, which is exclusively mitotic. * **Maturation:** This refers to **Spermiogenesis**, the morphological transformation of a spherical spermatid into a motile spermatozoon. It involves no cell division. **High-Yield Clinical Pearls for NEET-PG:** * **Spermatogonia to Spermatozoa:** The entire process takes approximately **74 days**. * **Blood-Testis Barrier:** Formed by **Sertoli cells** (tight junctions). It protects germ cells from the immune system, starting at the primary spermatocyte stage. * **Spermiation:** The process by which mature spermatozoa are released from Sertoli cells into the lumen of the seminiferous tubules. * **Chromosome Count:** Remember: Spermatogonia (46), Primary Spermatocyte (46), Secondary Spermatocyte (23), Spermatid (23).

Question 1

What is the best predictor of ovulation?

Accepted Answer

Onset of the LH surge

Answer

Estrogen peak

Answer

Follicle stimulating hormone (FSH) surge

Answer

Preovulatory rise in progesterone

Question 2

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

Accepted Answer

Granulosa cells

Answer

Interstitial cells

Answer

Luteal cells

Answer

Thecal cells

Question 3

Which cells produce Anti-Mullerian hormone in females?

Accepted Answer

Granulosa cells

Answer

Corpus luteum

Answer

Theca cells

Answer

Corona radiata

Question 4

What is characteristic of female oogenesis?

Accepted Answer

All of the above

Answer

Meiosis initiated once in a finite population of cells

Answer

One gamete produced per meiosis

Answer

Completion of meiosis delayed for months or years

Question 5

All of the following are indicators of ovulation except?

Accepted Answer

Fall in body temperature

Answer

Increase in cervical mucus

Answer

Abdominal cramps

Answer

LH surge

Question 6

What is the strongest stimulus of lactation?

Accepted Answer

Suckling

Answer

Metoclopramide

Answer

Postpartum hemorrhage

Answer

Bromocriptine

Question 7

What is the two-gonadotropin hypothesis?

Accepted Answer

FSH acts on granulosa cells and LH acts on theca cells.

Answer

FSH and LH inhibit the release of estrogen and progesterone.

Answer

FSH stimulates estrogen production, while LH inhibits estrogen production.

Answer

FSH provides negative feedback to the hypothalamus, while LH provides negative feedback to the pituitary.

Question 8

According to the World Health Organization 2010 strict criteria for semen analysis morphology, what percentage of normal forms is considered indicative?

Accepted Answer

>=4% normal forms

Answer

>15% normal forms

Answer

>=25% normal forms

Answer

>=32% normal forms

Question 9

Resolution of corpus luteum occurs because of:

Accepted Answer

Decreased levels of LH

Answer

Increased levels of progesterone

Answer

Increased levels of estrogen

Answer

Decreased levels of FSH

Question 10

What type of cell division is responsible for the early phase division of spermatogonia?

Accepted Answer

Mitosis

Answer

Meiosis

Answer

Both Meiosis and Mitosis

Answer

Maturation

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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