Reproductive Physiology Practice Questions

Q: The corpus luteum of menstruation persists for how many days?

14 days. **Explanation:** The correct answer is **14 days (Option C)**. The lifespan of the **corpus luteum of menstruation** is remarkably constant, regardless of the total length of the menstrual cycle. Following ovulation (triggered by the LH surge), the ruptured follicle transforms into the corpus luteum. This structure is programmed to function for approximately **12 to 14 days** (the luteal phase). If fertilization does not occur, the lack of Human Chorionic Gonadotropin (hCG) leads to the involution of the corpus luteum into the **corpus albicans**, resulting in a drop in progesterone and estrogen levels, which triggers menstruation. **Analysis of Incorrect Options:** * **Option A (5 days):** This is too short. The corpus luteum requires more time to secrete sufficient progesterone to prepare the endometrium for potential implantation. * **Option B (10 days):** While the corpus luteum begins to regress around day 9-10 post-ovulation if no pregnancy occurs, the functional lifespan and the subsequent onset of menses typically complete the 14-day window. * **Option D (30 days):** This exceeds the normal menstrual cycle length. A corpus luteum only persists beyond 14 days if pregnancy occurs (**corpus luteum of pregnancy**), where it is rescued by hCG for about 8–12 weeks. **NEET-PG High-Yield Pearls:** 1. **Fixed Luteal Phase:** While the follicular phase varies, the luteal phase is almost always **14 days**. This is why ovulation is calculated as *Expected Date of Menses minus 14 days*. 2. **Hormonal Control:** The formation and initial maintenance of the corpus luteum are dependent on **Luteinizing Hormone (LH)**. 3. **Luteolysis:** The process of corpus luteum degradation is called luteolysis, primarily driven by a decrease in LH support and local factors. 4. **Progesterone:** The corpus luteum is the primary source of progesterone, which is responsible for the "secretory phase" of the uterine cycle.

Q: Ovulation coincides with which hormonal event?

LH surge. **Explanation:** The correct answer is **D. LH surge**. Ovulation is the process where a mature follicle ruptures to release an oocyte. This event is triggered by a rapid rise in Luteinizing Hormone (LH), known as the **LH surge**. **Why LH surge is correct:** Under the influence of rising estrogen from the dominant follicle, a "positive feedback" mechanism is triggered on the anterior pituitary. This leads to a massive release of LH. The LH surge is essential because it: 1. Resumes meiosis I in the oocyte (completing it to metaphase II). 2. Stimulates prostaglandins and proteolytic enzymes (like collagenase) to weaken the follicular wall, leading to rupture. 3. Converts the remaining follicle into the corpus luteum (luteinization). **Why other options are incorrect:** * **A. Estrogen surge:** While an estrogen surge *precedes* the LH surge (occurring ~24–36 hours before ovulation), it is not the event that coincides with the actual rupture of the follicle. * **B. Progesterone surge:** Progesterone levels only begin to rise significantly *after* ovulation, secreted by the newly formed corpus luteum. * **C. FSH surge:** There is a concomitant rise in FSH during the LH surge, but it is less pronounced and its role in actual ovulation is secondary compared to the indispensable role of LH. **High-Yield Facts for NEET-PG:** * **Timing:** Ovulation occurs **10–12 hours after the LH peak** and **32–36 hours after the initial rise** in LH. * **Best Predictor:** The LH surge is the most reliable predictor of impending ovulation (used in ovulation predictor kits). * **Basal Body Temperature (BBT):** A rise in BBT (0.5–1.0°F) occurs *after* ovulation due to the thermogenic effect of **Progesterone**. * **Mittelschmerz:** Pelvic pain experienced by some women during ovulation due to follicular fluid or blood irritating the peritoneum.

Q: Endometrial repair after menstrual bleeding is primarily under the influence of which hormone?

Estrogen. **Explanation:** The correct answer is **Estrogen**. **1. Why Estrogen is Correct:** The menstrual cycle is divided into the follicular (proliferative) and luteal (secretory) phases. Following the shedding of the functional layer of the endometrium during menstruation, the **Proliferative Phase** begins. This phase is dominated by **Estrogen**, primarily secreted by the developing ovarian follicles. Estrogen stimulates the proliferation of the endometrial stromal cells and the growth of endometrial glands and blood vessels, effectively "repairing" and thickening the lining in preparation for potential implantation. **2. Why Other Options are Incorrect:** * **FSH (Follicle Stimulating Hormone):** While FSH stimulates the growth of ovarian follicles (which then produce estrogen), it does not have a direct trophic effect on the endometrial lining itself. * **Progesterone:** This hormone dominates the **Secretory Phase** (after ovulation). Its primary role is to differentiate the estrogen-primed endometrium into a secretory state, making it vascular and nutrient-rich. It does not initiate the initial repair/proliferation. * **LH (Luteinizing Hormone):** LH is responsible for triggering ovulation and maintaining the corpus luteum. It has no direct role in endometrial tissue repair. **Clinical Pearls for NEET-PG:** * **The "Triple Line" Appearance:** On ultrasound, the estrogen-driven proliferative endometrium typically shows a characteristic "triple-line" pattern. * **Estrogen vs. Progesterone:** Remember: Estrogen = **Proliferation** (growth in thickness); Progesterone = **Secretory changes** (functional maturation). * **Withdrawal Bleeding:** Menstruation occurs due to the sudden withdrawal of both estrogen and progesterone following the involution of the corpus luteum.

Q: Oxytocin causes all of the following except:

Lactogenesis. **Explanation:** The correct answer is **A. Lactogenesis**. **1. Why Lactogenesis is the correct (Except) option:** Lactogenesis refers to the initiation of milk secretion in the mammary glands. This process is primarily mediated by **Prolactin**, which is secreted by the anterior pituitary. Oxytocin has no role in the synthesis or initiation of milk production; its function is purely mechanical and related to smooth muscle contraction. **2. Analysis of Incorrect Options:** * **Milk ejection (B) & Myoepithelial cell contraction (D):** These are the primary functions of Oxytocin in the breast. Oxytocin is released from the posterior pituitary in response to suckling (the **Milk Ejection Reflex** or Ferguson Reflex). it causes contraction of the **myoepithelial cells** surrounding the alveoli, forcing milk into the ducts. * **Contraction of uterine muscle (C):** Oxytocin acts on the G-protein coupled receptors of the myometrium to increase intracellular calcium, leading to powerful uterine contractions. This is essential for both the progression of labor and the prevention of postpartum hemorrhage (PPH). **3. High-Yield Clinical Pearls for NEET-PG:** * **Site of Synthesis:** Oxytocin is synthesized in the **Paraventricular nucleus** (primarily) and Supraoptic nucleus of the hypothalamus, then stored in the posterior pituitary. * **The "Love Hormone":** Beyond physical labor, it plays a role in social bonding and maternal behavior. * **Pharmacology Link:** Synthetic oxytocin (Pitocin) is the drug of choice for **Induction of Labor** and management of **Postpartum Hemorrhage (PPH)**. * **Reflex Type:** The milk ejection reflex is a **neuroendocrine reflex**. Unlike most hormones, Oxytocin operates on a **positive feedback mechanism** during labor.

Q: Plasma levels of hCG during pregnancy double approximately every:

2 days. **Explanation:** Human Chorionic Gonadotropin (hCG) is a glycoprotein hormone secreted by the **syncytiotrophoblast** of the developing placenta. Its primary physiological role is to maintain the corpus luteum, ensuring the continued secretion of progesterone until the placenta takes over steroidogenesis (the luteal-placental shift). **Why Option B is Correct:** In a normal intrauterine pregnancy, serum hCG levels rise exponentially during the first trimester. The **doubling time** of hCG is approximately **48 hours (2 days)** during the early weeks of gestation. This rapid increase is a hallmark of a viable, healthy pregnancy. hCG levels typically peak between **8 to 12 weeks** of gestation before gradually declining to a lower, stable plateau for the remainder of the pregnancy. **Why Other Options are Incorrect:** * **Option A (Daily):** While hCG rises rapidly, a 24-hour doubling time is abnormally fast and not the physiological standard. * **Options C & D (4 or 6 days):** A doubling time longer than 2 days (e.g., >72 hours) in early pregnancy is often a clinical red flag. Slow-rising hCG levels are frequently associated with **ectopic pregnancy** or impending **spontaneous abortion**. **High-Yield Clinical Pearls for NEET-PG:** * **Detection:** hCG can be detected in maternal blood as early as **6–8 days after conception** (around the time of implantation) and in urine by day 14. * **Subunits:** hCG consists of an alpha and a beta subunit. The **beta (β) subunit** is unique to hCG, making it the basis for pregnancy tests (the alpha subunit is identical to LH, FSH, and TSH). * **Clinical Utility:** Serial hCG monitoring is the "gold standard" for evaluating early pregnancy complications. If the level fails to increase by at least 66% in 48 hours, the pregnancy's viability is guarded. * **Pathological Peaks:** Extremely high levels of hCG are seen in **Hydatidiform mole** (Gestational Trophoblastic Disease) and multiple pregnancies.

Q: Upon contact between the sperm head and the zona pellucida, penetration of the sperm into the egg is allowed because of which of the following processes?

The acrosome reaction. **Explanation:** The correct answer is **A. The acrosome reaction.** **1. Why the Acrosome Reaction is Correct:** When a capacitated sperm binds to the **ZP3 receptors** on the zona pellucida (ZP), it triggers the acrosome reaction. This involves the fusion of the outer acrosomal membrane with the sperm's plasma membrane, leading to the release of proteolytic enzymes (primarily **Acrosin** and Hyaluronidase). These enzymes locally digest the glycoprotein matrix of the zona pellucida, creating a tunnel that allows the sperm to penetrate and reach the oocyte's plasma membrane. **2. Why the Other Options are Incorrect:** * **B. The Zona Reaction:** This occurs *after* the first sperm penetrates the egg. It involves the release of cortical granules (Cortical Reaction) that harden the zona pellucida to prevent **polyspermy** (entry of multiple sperm). * **C. The Perivitelline Space:** This is the fluid-filled space between the zona pellucida and the oocyte cell membrane. It is a structural location, not a process that facilitates penetration. * **D. Pro-nuclei Formation:** This is a late stage of fertilization that occurs after the sperm has already entered the egg and the second meiotic division is completed. **3. NEET-PG High-Yield Pearls:** * **Capacitation:** A 7-hour process in the female reproductive tract (primarily the isthmus of the fallopian tube) required for the sperm to become fertile; it must precede the acrosome reaction. * **ZP3:** The specific glycoprotein receptor on the zona pellucida responsible for species-specific sperm binding. * **Calcium (Ca²⁺) Influx:** The essential ion required to trigger the acrosome reaction upon sperm-ZP binding.

Question 1

The corpus luteum of menstruation persists for how many days?

Accepted Answer

14 days

Answer

5 days

Answer

10 days

Answer

30 days

Question 2

Ovulation coincides with which hormonal event?

Accepted Answer

LH surge

Answer

Estrogen surge

Answer

Progesterone surge

Answer

FSH surge

Question 3

Maintenance of the corpus luteum during the first trimester of pregnancy is accomplished principally by the secretion of?

Accepted Answer

Human chorionic gonadotropin (hCG)

Answer

Antidiuretic hormone (ADH)

Answer

Follicle stimulating hormone (FSH)

Answer

Luteinizing hormone (LH)

Question 4

Endometrial repair after menstrual bleeding is primarily under the influence of which hormone?

Accepted Answer

Estrogen

Answer

FSH

Answer

Progesterone

Answer

LH

Question 5

Which of the following probably triggers the onset of labor?

Accepted Answer

ACTH in the fetus

Answer

ACTH in the mother

Answer

Oxytocin

Answer

Prostaglandin

Question 6

Oxytocin causes all of the following except:

Accepted Answer

Lactogenesis

Answer

Milk ejection

Answer

Contraction of uterine muscle

Answer

Myoepithelial cell contraction

Question 7

Which of the following statements regarding folliculogenesis and ovulation is INCORRECT?

Accepted Answer

Elevated and static levels of estradiol are essential for ovulation.

Answer

Follicular development and differentiation takes approximately 85 days.

Answer

AMH supports follicular development and oocyte maturation.

Answer

The first phase of follicular growth is gonadotropin-insensitive.

Question 8

Plasma levels of hCG during pregnancy double approximately every:

Accepted Answer

2 days

Answer

Daily

Answer

4 days

Answer

6 days

Question 9

Upon contact between the sperm head and the zona pellucida, penetration of the sperm into the egg is allowed because of which of the following processes?

Accepted Answer

The acrosome reaction

Answer

The zona reaction

Answer

The perivitelline space

Answer

Pro-nuclei formation

Question 10

Which of the following statements regarding human chorionic gonadotropin (HCG) is false?

Accepted Answer

It is secreted by syncytiotrophoblasts.

Answer

It acts on the same receptor as luteinizing hormone (LH).

Answer

It has a luteotrophic action.

Answer

It is a glycoprotein.

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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