Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 161: Inhibin is secreted by:

A. Graffian follicle (Correct Answer)
B. Corpus luteum
C. Endometrium
D. Placenta

Explanation: **Explanation:** **1. Why the Correct Answer is Right:** Inhibin is a glycoprotein hormone primarily involved in the negative feedback regulation of **Follicle-Stimulating Hormone (FSH)**. In females, **Inhibin B** is secreted by the **granulosa cells** of the developing antral follicles, reaching its peak during the mid-follicular phase in the **Graafian follicle**. Its primary role is to suppress FSH secretion from the anterior pituitary, which helps in the selection of the dominant follicle and prevents the over-stimulation of multiple follicles. **2. Why the Other Options are Wrong:** * **Corpus Luteum:** While the corpus luteum does secrete **Inhibin A** (dominant in the luteal phase), the standard physiological teaching for the primary source of inhibin in the context of the follicular cycle is the granulosa cells of the maturing follicle. * **Endometrium:** The endometrium is the target tissue for ovarian steroids (estrogen and progesterone) but does not synthesize or secrete inhibin. * **Placenta:** Although the placenta can produce various hormones (like hCG and hPL), it is not the primary physiological source of inhibin discussed in the context of the menstrual cycle. **3. High-Yield Clinical Pearls for NEET-PG:** * **Inhibin B vs. A:** Remember **B** for **B**efore ovulation (Follicular phase/Granulosa cells) and **A** for **A**fter ovulation (Luteal phase/Corpus luteum). * **Male Counterpart:** In males, Inhibin is secreted by the **Sertoli cells** of the testes to inhibit FSH. * **Clinical Marker:** Serum Inhibin B levels are used as a marker of **ovarian reserve**; low levels indicate a depleted follicular pool. * **Tumor Marker:** Inhibin is a highly specific tumor marker for **Granulosa Cell Tumors** of the ovary.

Question 162: Serum levels of different hormones estimated on the day of ovulation will depict which of the following?

A. FSH, LH, Estrogen and Progesterone (Correct Answer)
B. FSH, LH, Estrogen and Progesterone
C. FSH, LH, Estrogen and Progesterone
D. FSH, LH, Estrogen and Progesterone

Explanation: **Explanation:** The day of ovulation is characterized by a complex interplay of hormonal peaks. The correct answer reflects that **FSH, LH, Estrogen, and Progesterone are all elevated** (to varying degrees) on the day of ovulation compared to the early follicular phase. 1. **LH (Luteinizing Hormone):** The "LH Surge" is the primary trigger for ovulation. It peaks approximately 10–12 hours before ovulation. 2. **FSH (Follicle Stimulating Hormone):** There is a concomitant FSH surge (though smaller than LH) triggered by the rising GnRH and the positive feedback of estrogen. 3. **Estrogen:** Estrogen levels reach their absolute peak about 24–36 hours before ovulation. While they begin to decline slightly just before the egg is released, they remain significantly elevated compared to the baseline. 4. **Progesterone:** Traditionally associated with the luteal phase, progesterone actually begins to rise **just before** ovulation (pre-ovulatory rise) due to the luteinization of the granulosa cells under the influence of LH. This rise is essential for the FSH surge and the proteolytic enzymes that rupture the follicle. **Why other options are incorrect:** In the context of NEET-PG, questions often test whether you recognize that **Progesterone is not zero** during ovulation. Any option suggesting low progesterone or low estrogen on the day of ovulation would be physiologically inaccurate. **High-Yield Clinical Pearls for NEET-PG:** * **LH Surge:** The best predictor of ovulation (occurs 32–36 hours before follicle rupture). * **Estrogen Feedback:** Estrogen exerts **negative feedback** at low levels but switches to **positive feedback** (triggering the LH surge) when levels exceed 200 pg/mL for at least 48 hours. * **Mittelschmerz:** Pelvic pain associated with ovulation due to follicular fluid irritating the peritoneum. * **Basal Body Temperature (BBT):** Increases by 0.5–1.0°F *after* ovulation due to the thermogenic effect of progesterone.

Question 163: Primary oocyte remains arrested in the diplotene phase due to which of the following factors?

A. Oocyte maturation inhibitor (Correct Answer)
B. Oocyte maturation stimulator
C. Acetylcholine
D. Estrogen

Explanation: **Explanation:** **1. Why Option A is Correct:** During fetal life, primordial germ cells undergo mitosis to become oogonia, which then enter the first meiotic division to become **primary oocytes**. However, these oocytes do not complete meiosis I; they remain arrested in the **Prophase of Meiosis I (specifically the Diplotene stage)** until puberty. This arrest is primarily maintained by **Oocyte Maturation Inhibitor (OMI)**. OMI is a substance secreted by the surrounding **granulosa cells**. It acts by maintaining high levels of cyclic AMP (cAMP) within the oocyte, which prevents the activation of Maturation Promoting Factor (MPF), thereby keeping the oocyte in a state of meiotic dormancy. **2. Why Other Options are Incorrect:** * **Option B (Oocyte maturation stimulator):** This is a functional opposite. The "stimulator" for resuming meiosis is the **LH surge** during the menstrual cycle, which overcomes the inhibitory effect of OMI. * **Option C (Acetylcholine):** This is a neurotransmitter involved in the parasympathetic nervous system and muscle contraction; it has no established role in the meiotic arrest of oocytes. * **Option D (Estrogen):** While estrogen is vital for follicular development and the LH surge, it is not the direct biochemical factor responsible for the arrest in the diplotene stage. **3. High-Yield Clinical Pearls for NEET-PG:** * **Two Arrests:** Remember the "Two Meiotic Arrests": 1. **First Arrest:** Prophase I (Diplotene stage) – occurs before birth; ends at puberty (due to OMI). 2. **Second Arrest:** Metaphase II – occurs at ovulation; ends only if **fertilization** occurs. * **Dictyotene:** The prolonged diplotene stage in oogenesis is specifically referred to as the *dictyate* or *dictyotene* stage. * **The Trigger:** The resumption of Meiosis I is triggered by the **Pre-ovulatory LH surge**.

Question 164: During which period is vaginal pH most acidic?

A. Menstruation
B. Pregnancy (Correct Answer)
C. Puerperium
D. Newborn period

Explanation: **Explanation:** The acidity of the vaginal environment is primarily determined by the presence of **Lactobacillus (Döderlein’s bacilli)**, which convert glycogen into lactic acid. **Why Pregnancy is the Correct Answer:** During pregnancy, there is a massive surge in **estrogen** levels. Estrogen increases the deposition of **glycogen** in the vaginal epithelial cells. This abundance of substrate allows Lactobacilli to produce high amounts of lactic acid, dropping the vaginal pH to its most acidic levels (typically between **3.5 and 4.5**). This acidic environment serves as a protective mechanism against ascending infections during gestation. **Analysis of Incorrect Options:** * **Menstruation:** The presence of blood (which is alkaline) and the shedding of the functional layer of the epithelium raise the pH toward neutrality or alkalinity (approx. 7.0). * **Puerperium:** Following delivery, estrogen levels drop sharply, and the presence of lochia (alkaline discharge) keeps the vaginal pH high, making the area more susceptible to infection. * **Newborn Period:** While a newborn has temporary acidity due to maternal estrogens, this effect fades quickly. Throughout childhood (pre-puberty), the vaginal pH remains neutral or alkaline (around 7.0) due to low estrogen and lack of glycogen. **High-Yield NEET-PG Pearls:** * **Estrogen = Glycogen = Acidity:** The vaginal pH is acidic only during periods of high estrogen (puberty to menopause, and peak during pregnancy). * **Progesterone** tends to decrease the glycogen content, slightly counteracting the estrogenic effect, but the net effect in pregnancy remains highly acidic. * **Clinical Correlation:** A rise in vaginal pH (>4.5) is a diagnostic hallmark for **Bacterial Vaginosis** and **Trichomoniasis**, whereas the pH remains normal (<4.5) in **Vulvovaginal Candidiasis**.

Question 165: Which statement is true about spermatogenesis?

A. It takes 74 days to complete. (Correct Answer)
B. It takes place in the spermatic cord.
C. Meiosis occurs only after the formation of the secondary spermatocyte.
D. Spermatids are formed from spermatozoa.

Explanation: ### Explanation **1. Why Option A is Correct:** Spermatogenesis is the process by which male spermatogonia develop into mature spermatozoa. In humans, the entire process—from the initial division of a spermatogonium to the release of a mature sperm cell into the lumen—takes approximately **74 days**. This timeline is a high-yield physiological constant often tested in exams. **2. Why the Other Options are Incorrect:** * **Option B:** Spermatogenesis occurs exclusively within the **seminiferous tubules** of the testes. The spermatic cord is a collection of structures (including the vas deferens and pampiniform plexus) that suspends the testis in the scrotum; it does not produce sperm. * **Option C:** Meiosis begins with the **primary spermatocyte**. The first meiotic division (reductional) converts a primary spermatocyte into two secondary spermatocytes. The second meiotic division then converts these into spermatids. * **Option D:** This is reversed. **Spermatozoa are formed from spermatids** through a process of morphological maturation called **spermiogenesis** (involving acrosome formation and tail development). **3. NEET-PG High-Yield Pearls:** * **Spermiogenesis vs. Spermatogenesis:** Spermiogenesis is specifically the transformation of a spermatid into a spermatozoon (no cell division occurs here). * **Spermiation:** The process by which mature spermatozoa are released from Sertoli cells into the seminiferous tubule lumen. * **Hormonal Control:** LH stimulates **Leydig cells** to produce testosterone; FSH stimulates **Sertoli cells** to support spermatogenesis and produce Androgen Binding Protein (ABP). * **Temperature:** Optimal spermatogenesis requires a temperature **2–3°C lower** than core body temperature.

Question 166: What is the lifespan of a sperm for fertilization?

A. 24 hours
B. 48 hours
C. 72 hours (Correct Answer)
D. 96 hours

Explanation: **Explanation:** The lifespan of a sperm cell within the female reproductive tract is a critical concept in reproductive physiology. While sperm can remain motile for longer periods, their **functional capacity for fertilization** (fertilizing life) is generally considered to be **48 to 72 hours**. **1. Why 72 hours is correct:** After ejaculation into the vagina, sperm undergo **capacitation**—a series of biochemical changes in the female tract that enable them to penetrate the zona pellucida of the oocyte. While individual variations exist, standard medical texts (like Guyton and Ganong) emphasize that sperm typically retain their ability to fertilize the ovum for up to **3 days (72 hours)**. Beyond this window, even if the sperm remains motile, its metabolic reserves are depleted, and its membrane integrity declines, making fertilization unlikely. **2. Analysis of Incorrect Options:** * **24 hours (A):** This is the typical lifespan of the **ovum (oocyte)** after ovulation, not the sperm. The ovum must be fertilized within 12–24 hours to ensure a viable pregnancy. * **48 hours (B):** While many sperm lose potency by 48 hours, the physiological upper limit for the "fertile window" in a healthy male is traditionally taught as 72 hours for competitive exams. * **96 hours (D):** Although rare cases of survival up to 5 days have been documented in cervical mucus, it is not the physiological standard for fertilization capacity. **3. High-Yield Clinical Pearls for NEET-PG:** * **Sperm Maturation:** Sperm acquire *motility* in the **epididymis** but achieve *fertilization competence* via **capacitation** in the female reproductive tract (uterus/fallopian tubes). * **Storage:** In the male reproductive tract (epididymis/vas deferens), sperm can remain viable but suppressed for up to **month**. * **The Fertile Window:** Considering the 72-hour sperm life and 24-hour ovum life, the "fertile window" typically spans 4–5 days surrounding ovulation.

Question 167: Which statement is true regarding estrogen production during the menstrual cycle?

A. Estrogen is produced solely by theca cells.
B. Estrogen is produced solely by granulosa cells. (Correct Answer)
C. Estrogen is produced by both theca and granulosa cells.
D. None of the above.

Explanation: ### Explanation The production of estrogen in the ovary is governed by the **Two-Cell, Two-Gonadotropin Theory**. This process requires the coordinated action of both theca and granulosa cells, but the final synthesis of estrogen occurs **solely within the granulosa cells**. **1. Why the Correct Answer is Right:** * **Theca Cells:** Under the influence of **LH**, these cells take up cholesterol and convert it into androgens (androstenedione and testosterone). Theca cells lack the enzyme **aromatase**, so they cannot produce estrogen themselves. * **Granulosa Cells:** Under the influence of **FSH**, these cells take up the androgens produced by the theca cells. Granulosa cells contain high levels of **aromatase**, which converts these androgens into estrogens (estradiol and estrone). Since the final conversion step happens only here, the granulosa cell is the site of estrogen production. **2. Why Incorrect Options are Wrong:** * **Option A:** Theca cells lack aromatase; they can only produce androgen precursors. * **Option C:** While both cells are *involved* in the pathway, the actual production (synthesis) of the final hormone, estrogen, is localized to the granulosa cells. In the context of "production" in physiological exams, the site of the final enzymatic conversion is the defining factor. **3. High-Yield NEET-PG Pearls:** * **LH** acts on **L**eydig/Theca cells (Androgen synthesis). * **FSH** acts on **S**ertoli/Granulosa cells (Spermatogenesis/Oogenesis and Aromatization). * **Dominant Follicle:** The follicle with the highest concentration of FSH receptors and aromatase activity becomes the dominant follicle. * **Estrogen Feedback:** Low levels of estrogen inhibit LH/FSH (negative feedback), but high levels for >48 hours trigger the **LH surge** (positive feedback).

Question 168: Semen examination of a man showed counts of 25 million/cu.mm, volume - 1.5 ml; motility - 15%; Morphology - 15%. What is the diagnosis?

A. Azoospermia
B. Asthenospermia (Correct Answer)
C. Oligospermia
D. Teratospermia

Explanation: To answer this question correctly, we must compare the patient's values against the **WHO (2010/2021) criteria** for normal semen analysis. ### **Analysis of Parameters** 1. **Sperm Count:** The patient has **25 million/ml**. The lower reference limit is **15 million/ml**. Therefore, the count is **normal**. 2. **Motility:** The patient has **15%** motility. The lower reference limit is **40%** (total motility) or **32%** (progressive motility). This is significantly **low**. 3. **Morphology:** The patient has **15%** normal forms. The lower reference limit is **4%** (Kruger’s strict criteria). Therefore, morphology is **normal**. 4. **Volume:** 1.5 ml is the lower limit of normal. ### **Why Asthenospermia is Correct** **Asthenospermia** (or Asthenozoospermia) is defined as reduced sperm motility. Since the only abnormal parameter in this patient is the low motility (15%), this is the primary diagnosis. ### **Why Other Options are Incorrect** * **Azoospermia:** Refers to the total absence of spermatozoa in the ejaculate. This patient has 25 million/ml. * **Oligospermia:** Refers to a low sperm count (<15 million/ml). This patient’s count is within the normal range. * **Teratospermia:** Refers to poor sperm morphology (<4% normal forms). This patient has 15% normal morphology, which is healthy. ### **High-Yield Clinical Pearls for NEET-PG** * **Oligoasthenoteratozoospermia (OAT):** A condition where all three variables (count, motility, and morphology) are subnormal. * **Aspermia:** Complete absence of semen (no ejaculate), not to be confused with Azoospermia. * **Hypospermia:** Semen volume <1.5 ml. * **Hematospermia:** Presence of blood in semen (commonly associated with prostatic inflammation). * **Fructose in Semen:** Produced by seminal vesicles; its absence suggests bilateral congenital absence of the vas deferens or ejaculatory duct obstruction.

Question 169: Serum inhibin B is secreted by ovarian granulosa cells starting at which stage?

A. Primordial follicle stage
B. Preantral follicle stage (Correct Answer)
C. Early antral stage
D. Preovulatory stage

Explanation: **Explanation:** The secretion of Inhibin B is a key marker of follicular development and ovarian reserve. **1. Why Preantral Follicle Stage is Correct:** Inhibin B is produced by the **granulosa cells** of small, developing follicles. Its secretion begins at the **preantral (primary/secondary) follicle stage**, as soon as the granulosa cells begin to proliferate and differentiate under the initial influence of FSH. Inhibin B serves as a primary feedback regulator, suppressing FSH secretion from the anterior pituitary to ensure that only the most sensitive follicles continue to grow. **2. Analysis of Incorrect Options:** * **Primordial follicle stage:** These follicles are "resting" and consist of an oocyte surrounded by a single layer of flattened pre-granulosa cells. They are metabolically quiet and do not secrete significant amounts of inhibin. * **Early antral stage:** While Inhibin B levels peak during the early antral stage (recruitment phase), its *secretion* actually begins earlier, during the preantral transition. * **Preovulatory stage:** This stage is dominated by **Inhibin A**. While Inhibin B is the marker of the follicular phase (secreted by small follicles), Inhibin A is the marker of the luteal phase (secreted by the dominant follicle and corpus luteum). **3. High-Yield Clinical Pearls for NEET-PG:** * **Inhibin B:** Secreted by granulosa cells of **small follicles**; peaks in the **early follicular phase**. It is a marker of the *quantity* of the ovarian reserve. * **Inhibin A:** Secreted by the **dominant follicle** and **corpus luteum**; peaks in the **mid-luteal phase**. * **Clinical Use:** Low Day-3 Inhibin B levels are associated with poor response to ovulation induction and declining ovarian reserve. * **Tumor Marker:** Inhibins are used as serum markers for **Granulosa Cell Tumors** of the ovary.

Question 170: Which of the following is NOT a function of estrogen?

A. Stimulation of secretory function on the endometrium (Correct Answer)
B. Stimulation of synthetic function on the endometrium
C. Development of secondary sexual characters in females
D. Breast enlargement during puberty

Explanation: **Explanation:** The key to answering this question lies in distinguishing between the **proliferative** effects of estrogen and the **secretory** effects of progesterone on the uterine lining. **1. Why Option A is the Correct Answer:** Estrogen is primarily responsible for the **proliferative phase** of the menstrual cycle. It stimulates the growth and synthetic activity of the endometrial lining (increasing thickness, vascularity, and DNA synthesis). However, the **secretory transformation**—characterized by the coiling of endometrial glands and the secretion of glycogen-rich fluids—is strictly a function of **Progesterone** during the luteal phase. Therefore, estrogen does not stimulate secretory function. **2. Analysis of Incorrect Options:** * **Option B:** Estrogen promotes the **synthetic function** of the endometrium by inducing the synthesis of RNA, proteins, and DNA, leading to cellular hyperplasia and hypertrophy. * **Option C:** Estrogen is the primary hormone responsible for the **development of secondary sexual characteristics** in females, including the widening of the pelvis and female-pattern fat distribution. * **Option D:** At puberty, estrogen stimulates the **growth of mammary ducts** and the deposition of fat in the breasts, leading to breast enlargement (Thelarche). **Clinical Pearls for NEET-PG:** * **Estrogen vs. Progesterone:** Estrogen = Duct growth in breasts; Progesterone = Alveolar/Lobular development. * **Cervical Mucus:** Estrogen makes mucus thin, watery, and alkaline (shows **ferning**), whereas progesterone makes it thick and cellular. * **Bone Health:** Estrogen promotes the closure of epiphyseal plates and inhibits osteoclast activity (preventing osteoporosis).

Practice by Chapter

Male Reproductive Physiology

Practice Questions

Spermatogenesis and Sperm Function

Practice Questions

Female Reproductive Physiology

Practice Questions

Menstrual Cycle

Practice Questions

Ovulation and Fertilization

Practice Questions

Physiology of Pregnancy

Practice Questions

Parturition

Practice Questions

Lactation

Practice Questions

Sexual Differentiation and Development

Practice Questions

Reproductive Aging

Practice Questions

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