Reproductive Physiology — MCQs
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Which of the following arteries supplying the uterus is insensitive to hormonal changes?
What hormonal changes are characteristic of the luteal phase?
What is the earliest hormonal sign of puberty?
The corpus luteum of menstruation persists for how many days?
Ovulation coincides with which hormonal event?
In a woman with a 28-day menstrual cycle, at what point does ovulation typically occur?
Maintenance of the corpus luteum during the first trimester of pregnancy is accomplished principally by the secretion of?
What is the ploidy of the secondary oocyte and the amount of DNA it contains?
Endometrial repair after menstrual bleeding is primarily under the influence of which hormone?
Which of the following probably triggers the onset of labor?
Reproductive Physiology Indian Medical PG Practice Questions and MCQs
Question 311: Which of the following arteries supplying the uterus is insensitive to hormonal changes?
- A. Radial arteries
- B. Spiral arteries
- C. Basal arteries (Correct Answer)
- D. None of the above
Explanation: The uterine blood supply is organized into distinct layers, and understanding the functional anatomy of the endometrium is crucial for NEET-PG. **Explanation of the Correct Answer:** The endometrium is divided into two layers: the **stratum basalis** (deep) and the **stratum functionalis** (superficial). The **Basal arteries** supply the stratum basalis. These arteries are **insensitive to hormonal changes** (estrogen and progesterone). Because they do not constrict or undergo necrosis during the late luteal phase, the basal layer remains intact during menstruation, serving as the regenerative source for the new endometrium in the subsequent cycle. **Analysis of Incorrect Options:** * **Spiral arteries:** These supply the stratum functionalis. They are **highly sensitive** to hormonal fluctuations. When progesterone levels drop at the end of the cycle, these arteries undergo intense vasoconstriction and rhythmic spasms, leading to ischemia and the shedding of the functional layer (menstruation). * **Radial arteries:** These arise from the arcuate arteries and penetrate the myometrium. They are the parent vessels that branch into both basal and spiral arteries. While they are not the primary site of menstrual shedding, the question specifically targets the endometrial vessels where the distinction in hormonal sensitivity is a defining physiological characteristic. **High-Yield Clinical Pearls for NEET-PG:** * **Regeneration:** The stratum basalis (supplied by basal arteries) is the "permanent" layer; the stratum functionalis (supplied by spiral arteries) is the "deciduous" layer. * **Menstrual Mechanism:** The withdrawal of progesterone causes the release of **Prostaglandin F2α**, which triggers the vasospasm of the spiral arteries. * **Vascular Path:** Uterine artery → Arcuate artery → Radial artery → Basal/Spiral artery.
Question 312: What hormonal changes are characteristic of the luteal phase?
- A. Increased progesterone levels (Correct Answer)
- B. Decreased progesterone levels
- C. Decreased estrogen level
- D. None of the above
Explanation: The luteal phase (secretory phase) is the second half of the menstrual cycle, occurring after ovulation. Understanding its hormonal profile is crucial for NEET-PG. ### **Explanation of the Correct Answer** **A. Increased progesterone levels:** Following ovulation, the remains of the Graafian follicle transform into the **corpus luteum** under the influence of Luteinizing Hormone (LH). The corpus luteum acts as a temporary endocrine gland, primarily secreting large amounts of **progesterone**. Progesterone is essential for preparing the endometrium for implantation by increasing its vascularity and secretory activity. This is why the luteal phase is often referred to as the "progestational" phase. ### **Why Other Options are Incorrect** * **B. Decreased progesterone levels:** Progesterone levels are low during the follicular phase and only rise significantly after ovulation. A decrease in progesterone only occurs at the very end of the luteal phase (luteolysis) if fertilization does not occur, triggering menstruation. * **C. Decreased estrogen level:** While progesterone is the dominant hormone, estrogen levels actually show a **secondary rise** during the mid-luteal phase (secreted by the corpus luteum). They do not decrease below follicular levels until the onset of menses. ### **High-Yield Clinical Pearls for NEET-PG** * **Duration:** The luteal phase is remarkably constant at **14 days**. Variations in cycle length are usually due to variations in the follicular phase. * **Basal Body Temperature (BBT):** The rise in progesterone during this phase has a **thermogenic effect**, raising the BBT by approximately 0.5°F to 1.0°F. * **Hormonal Peak:** Both progesterone and estrogen reach their peak levels approximately **7–8 days after ovulation** (Day 21 of a 28-day cycle), which is the ideal time to test serum progesterone to confirm ovulation. * **Luteal-Placental Shift:** If pregnancy occurs, hCG maintains the corpus luteum until the placenta takes over progesterone production at around 7–10 weeks of gestation.
Question 313: What is the earliest hormonal sign of puberty?
- A. Sleep-associated increase in LH (Correct Answer)
- B. Early morning rise in temperature
- C. Increased FSH to LH ratio
- D. Elevated adrenal androgens
Explanation: ### Explanation The onset of puberty is triggered by the reactivation of the **GnRH pulse generator** (the "gonadostat") in the hypothalamus. **1. Why Option A is Correct:** The earliest detectable hormonal change of puberty is the **nocturnal (sleep-associated) increase in the pulsatile secretion of Luteinizing Hormone (LH)**. Initially, these pulses occur only during REM sleep. As puberty progresses, the amplitude and frequency of these LH pulses increase and eventually occur throughout the day and night. This shift marks the transition from the prepubertal state to active puberty. **2. Why Other Options are Incorrect:** * **Option B:** Early morning rise in temperature is associated with ovulation (progesterone effect) in the luteal phase of the menstrual cycle, not the onset of puberty. * **Option C:** In the **prepubertal** period, FSH levels are higher than LH levels. At the **onset of puberty**, this ratio reverses, and **LH becomes dominant** over FSH. Therefore, a *decreased* FSH to LH ratio is seen in puberty. * **Option D:** Elevated adrenal androgens (DHEA, DHEAS) characterize **Adrenarche**, which typically occurs around age 6–8. While it precedes puberty, it is a separate physiological process and not the hormonal trigger for true gonadal puberty (Gonadarche). ### High-Yield Clinical Pearls for NEET-PG: * **First Physical Sign (Females):** Thelarche (breast bud development), driven by Estrogen. * **First Physical Sign (Males):** Increase in testicular volume (>4 ml), driven by Testosterone. * **Order of Puberty (Females):** Thelarche → Pubarche → Growth Spurt → Menarche. * **Leptin's Role:** Adequate body fat and leptin levels are permissive for the onset of puberty by stimulating GnRH release.
Question 314: The corpus luteum of menstruation persists for how many days?
- A. 5 days
- B. 10 days
- C. 14 days (Correct Answer)
- D. 30 days
Explanation: **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.
Question 315: Ovulation coincides with which hormonal event?
- A. Estrogen surge
- B. Progesterone surge
- C. FSH surge
- D. LH surge (Correct Answer)
Explanation: **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.
Question 316: In a woman with a 28-day menstrual cycle, at what point does ovulation typically occur?
- A. 14 days prior to menstruation (Correct Answer)
- B. Just before the LH surge
- C. Just after corpus luteum maturation
- D. Due to progesterone rise
Explanation: ### Explanation **1. Why Option A is Correct:** The menstrual cycle consists of a variable follicular phase and a **constant luteal phase**. In a typical 28-day cycle, ovulation occurs on day 14. However, the physiological rule is that ovulation occurs exactly **14 days before the onset of the next menses**. This is because the lifespan of the corpus luteum is fixed at approximately 14 days (range 12–16 days). Therefore, regardless of whether a woman has a 21-day or a 35-day cycle, the period from ovulation to menstruation remains constant. **2. Why the Other Options are Incorrect:** * **Option B:** Ovulation occurs **after** the LH surge, not before it. The LH surge is the primary trigger for the release of the secondary oocyte; ovulation typically occurs 10–12 hours after the LH peak or 32–36 hours after the initial rise in LH. * **Option C:** The corpus luteum forms **after** ovulation has occurred (from the remnants of the Graafian follicle). It reaches functional maturity about 7–8 days post-ovulation. * **Option D:** Progesterone rise is a **consequence** of ovulation, not the cause. Progesterone is secreted by the corpus luteum to prepare the endometrium for implantation. **3. NEET-PG High-Yield Pearls:** * **The Trigger:** The LH surge is triggered by a "positive feedback" effect of Estrogen (when levels exceed 200 pg/mL for >48 hours). * **The Marker:** A rise in **Basal Body Temperature (BBT)** by 0.5–1.0°F (due to the thermogenic effect of progesterone) is a retrospective indicator that ovulation has occurred. * **The Gold Standard:** The most reliable clinical method to confirm ovulation is a **Mid-luteal Progesterone** assay (measured on day 21 of a 28-day cycle). * **Mittelschmerz:** Unilateral pelvic pain experienced by some women during ovulation.
Question 317: Maintenance of the corpus luteum during the first trimester of pregnancy is accomplished principally by the secretion of?
- A. Antidiuretic hormone (ADH)
- B. Follicle stimulating hormone (FSH)
- C. Human chorionic gonadotropin (hCG) (Correct Answer)
- D. Luteinizing hormone (LH)
Explanation: **Explanation:** The maintenance of the corpus luteum is critical for a successful pregnancy because it secretes **progesterone**, which supports the endometrial lining until the placenta takes over steroidogenesis (the luteal-placental shift) at approximately 8–12 weeks. **Why hCG is the correct answer:** In a non-pregnant cycle, the corpus luteum degenerates due to a lack of LH support. However, if fertilization occurs, the **syncytiotrophoblast** of the developing embryo secretes **Human Chorionic Gonadotropin (hCG)**. hCG is structurally similar to LH (sharing the same alpha subunit and a similar beta subunit) and binds to the same LH/hCG receptors on the corpus luteum. This "rescues" the corpus luteum, ensuring continued progesterone production throughout the first trimester. **Analysis of Incorrect Options:** * **ADH (Antidiuretic Hormone):** Produced by the hypothalamus and released by the posterior pituitary, its primary role is water reabsorption in the kidney; it has no role in maintaining the corpus luteum. * **FSH (Follicle Stimulating Hormone):** FSH is responsible for follicular recruitment and growth in the early follicular phase. During pregnancy, high levels of estrogen and progesterone suppress FSH via negative feedback. * **LH (Luteinizing Hormone):** While LH maintains the corpus luteum during the normal menstrual cycle, its levels drop during pregnancy due to feedback inhibition. hCG takes over this role because it has a much longer half-life and higher potency than LH. **High-Yield NEET-PG Pearls:** * **Luteal-Placental Shift:** Occurs between **7–10 weeks** of gestation. Before this, the corpus luteum is indispensable. * **hCG Structure:** It is a glycoprotein with $\alpha$ and $\beta$ subunits. The **$\beta$-subunit** is unique and is what pregnancy tests detect. * **Doubling Time:** In early normal pregnancy, serum hCG levels roughly double every **48 hours**, peaking at around **10 weeks**.
Question 318: What is the ploidy of the secondary oocyte and the amount of DNA it contains?
- A. Haploid (n) and 1N DNA content
- B. Haploid (n) and 2N DNA content (Correct Answer)
- C. Diploid (2n) and 1N DNA content
- D. Diploid (2n) and 2N DNA content
Explanation: ### Explanation The correct answer is **B: Haploid (n) and 2N DNA content.** #### 1. Understanding the Concept To master this high-yield topic, distinguish between **ploidy** (number of sets of chromosomes) and **DNA content** (amount of genetic material). * **Primary Oocyte:** Before Meiosis I, the cell is diploid (**2n**) and has replicated its DNA (**4N**). * **Secondary Oocyte:** Formed after the completion of **Meiosis I** (just before ovulation). During Meiosis I, homologous chromosomes separate. This reduces the chromosome number by half, making the cell **Haploid (n)**. However, each chromosome still consists of **two sister chromatids** joined at the centromere. Therefore, the DNA content is **2N**. The DNA content only reduces to **1N** after **Meiosis II** is completed (which occurs only upon fertilization), where sister chromatids finally separate. #### 2. Why Other Options are Incorrect * **Option A:** This describes a mature gamete (Ootid/Ovum) after fertilization and second polar body extrusion. * **Option C:** This combination is biologically impossible in the standard oogenesis timeline. * **Option D:** This describes a somatic cell in the G1 phase or a resting primary oocyte before DNA replication. #### 3. NEET-PG High-Yield Pearls * **Meiotic Arrests:** * Primary oocytes are arrested in **Prophase I (Dictyotene stage)** from fetal life until puberty. * Secondary oocytes are arrested in **Metaphase II** until fertilization. * **Trigger for Completion:** The surge of **LH** triggers the completion of Meiosis I; **Fertilization** (sperm entry) triggers the completion of Meiosis II. * **Polar Bodies:** The first polar body is also haploid (n) with 2N DNA, representing the "discarded" genetic material during the first division.
Question 319: Endometrial repair after menstrual bleeding is primarily under the influence of which hormone?
- A. FSH
- B. Progesterone
- C. Estrogen (Correct Answer)
- D. LH
Explanation: **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.
Question 320: Which of the following probably triggers the onset of labor?
- A. ACTH in the fetus (Correct Answer)
- B. ACTH in the mother
- C. Oxytocin
- D. Prostaglandin
Explanation: ### Explanation The initiation of parturition (labor) is a complex process, but in humans and many mammals, the **"placental clock"** is primarily driven by the fetus. **1. Why "ACTH in the fetus" is correct:** The onset of labor is triggered by the activation of the **Fetal Hypothalamic-Pituitary-Adrenal (HPA) axis**. Near term, the fetal hypothalamus increases the secretion of Corticotropin-Releasing Hormone (CRH), which stimulates the fetal anterior pituitary to release **ACTH**. This ACTH acts on the fetal adrenal glands to produce **Cortisol** and **DHEAS**. * **Cortisol** accelerates lung maturation and shifts placental steroidogenesis from progesterone (which maintains pregnancy) to estrogen. * **DHEAS** is converted into Estrogen by the placenta. The rising Estrogen-to-Progesterone ratio increases oxytocin receptors and gap junctions in the myometrium, effectively "priming" the uterus for labor. **2. Why the other options are incorrect:** * **ACTH in the mother:** Maternal ACTH does not cross the placenta in significant amounts and does not play a primary role in triggering the fetal-placental changes required for labor. * **Oxytocin:** While oxytocin is the most potent stimulator of uterine contractions and is essential for the *progression* and *maintenance* of labor (and the Ferguson reflex), it is generally considered an **effector** rather than the initial trigger. * **Prostaglandins:** Like oxytocin, prostaglandins (PGE2 and PGF2α) are critical for cervical ripening and augmenting contractions, but their synthesis is increased as a *result* of the hormonal shifts initiated by the fetal HPA axis. **High-Yield NEET-PG Pearls:** * **CRH Paradox:** Unlike the adult system where cortisol inhibits CRH, in the placenta, cortisol **stimulates** CRH production, creating a positive feedback loop that accelerates labor. * **Ferguson Reflex:** This is the neuroendocrine reflex where stretching of the cervix triggers oxytocin release from the maternal posterior pituitary. * **Quiescence:** Progesterone is the primary hormone responsible for maintaining uterine quiescence during pregnancy.
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
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Physiology of Pregnancy
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Parturition
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Lactation
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Sexual Differentiation and Development
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Reproductive Aging
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