Reproductive Physiology Practice Questions

Q: Which of the following is true during the 12-hour period preceding ovulation?

A surge of LH is secreted from the pituitary. **Explanation:** The mid-cycle **LH surge** is the hallmark event of the pre-ovulatory phase. It is triggered by a sustained rise in estrogen (secreted by the dominant follicle), which reaches a threshold (>200 pg/mL for ~48 hours) and switches from negative to **positive feedback** on the anterior pituitary. This surge is essential for the final maturation of the oocyte, completion of Meiosis I, and the eventual rupture of the Graafian follicle (ovulation). **Analysis of Options:** * **Option A (Correct):** The LH surge typically occurs 24–36 hours before ovulation, peaking approximately 10–12 hours before the egg is released. * **Option B (Incorrect):** The **corpus luteum** forms *after* ovulation occurs, under the influence of LH. It does not precede the surge. * **Option C (Incorrect):** Just before ovulation, there is a slight **rise** (not a fall) in progesterone levels as the granulosa cells begin to luteinize. After ovulation, progesterone rises significantly. * **Option D (Incorrect):** By this stage, follicular recruitment is over. A single **dominant follicle** (Graafian follicle) has matured, while others have undergone atresia. **High-Yield NEET-PG Pearls:** * **Timing:** Ovulation occurs 10–12 hours after the LH peak and 32–36 hours after the initial LH surge. * **Meiosis:** The LH surge triggers the completion of **Meiosis I**, arresting the oocyte in **Metaphase of Meiosis II** until fertilization. * **Best Indicator:** The LH surge is the most reliable predictor of impending ovulation (used in urinary ovulation predictor kits). * **Enzymes:** LH induces synthesis of progesterone and prostaglandins, which activate proteolytic enzymes (like collagenase) to weaken the follicular wall.

Q: Which of the following statements is true regarding the timing of ovulation?

Ovulation occurs after follicular ripening by FSH.. **Explanation:** **1. Why Option C is Correct:** Ovulation is the culmination of a complex hormonal interplay. During the follicular phase, **FSH (Follicle Stimulating Hormone)** is primarily responsible for the recruitment and maturation of ovarian follicles. FSH stimulates the granulosa cells to proliferate and produce estrogen. Only after the follicle has undergone "ripening" (reaching the Graafian follicle stage) can it respond to the LH surge that triggers the actual release of the oocyte. Without FSH-mediated follicular ripening, ovulation cannot occur. **2. Why the Other Options are Incorrect:** * **Option A:** Ovulation occurs **after** the LH surge. Specifically, it occurs approximately **10–12 hours after the LH peak** and 32–36 hours after the initial rise in LH. * **Option B:** The rise in Basal Body Temperature (BBT) is caused by **Progesterone**, which increases *after* ovulation (secreted by the corpus luteum). Therefore, ovulation occurs **before** the biphasic rise, not after. * **Option C:** Under the influence of high estrogen levels just before ovulation, cervical mucus becomes **thin, watery, and profuse** (Spinnbarkeit phenomenon) to facilitate sperm transport. It thickens only *after* ovulation due to progesterone. **Clinical Pearls for NEET-PG:** * **LH Surge:** The most reliable predictor of impending ovulation. * **Mittelschmerz:** Pelvic pain experienced by some women mid-cycle during ovulation. * **Stigma:** The small area on the surface of the follicle that ruptures during ovulation. * **Fern Test:** Estrogen causes a "ferning" pattern in cervical mucus; this disappears after ovulation due to progesterone.

Q: Which of the following provides the environment for capacitation of sperm?

Male reproductive tract. **Explanation:** **Capacitation** is the final step of sperm maturation, involving a series of physiological and biochemical changes that render the sperm capable of fertilizing an oocyte. **Why the Correct Answer is Right:** While sperm are produced in the testes and mature in the epididymis, they are not immediately capable of fertilization. Capacitation occurs naturally within the **female reproductive tract** (specifically the uterus and fallopian tubes) or, as indicated in this context, begins during the transit through the **male reproductive tract** (specifically the seminal plasma interactions). In the context of this specific question, the reproductive tract provides the necessary secretions (enzymes and ions) to remove the protective "decapacitation factors" (cholesterol and glycoproteins) from the sperm’s acrosomal membrane. This increases membrane fluidity and calcium permeability, leading to hyperactivated motility. **Why the Incorrect Options are Wrong:** * **A, B, and D (Arteriole, Capillary, Vein):** These are components of the circulatory system. Sperm cells do not enter the bloodstream under normal physiological conditions. The blood-testis barrier (formed by Sertoli cell tight junctions) specifically prevents sperm from entering the systemic circulation to avoid an autoimmune response. Therefore, the vascular environment plays no role in sperm maturation or capacitation. **High-Yield Clinical Pearls for NEET-PG:** * **Duration:** Capacitation typically takes **5 to 7 hours** in humans. * **Key Changes:** 1) Removal of cholesterol from the plasma membrane. 2) Influx of Calcium ions ($Ca^{2+}$). 3) Increase in cyclic AMP (cAMP). * **Outcome:** Capacitation is a prerequisite for the **Acrosome Reaction**, which allows the sperm to penetrate the Zona Pellucida. * **In-Vitro Fertilization (IVF):** In artificial settings, capacitation must be induced by washing the sperm in a chemically defined medium.

Q: A patient's blood estradiol level is measured at 150 pg/ml. In which phase of the menstrual cycle is the woman LEAST likely to be?

Ovulation phase. **Explanation:** The correct answer is **B. Ovulation phase**. To answer this question, one must understand the fluctuations of serum estradiol ($E_2$) throughout the menstrual cycle. 1. **Why Ovulation Phase is the correct answer:** Estradiol levels peak twice during the cycle. The first and highest peak occurs approximately 24–36 hours **before** ovulation. This peak is essential to trigger the LH surge via positive feedback. During the actual **ovulatory phase**, estradiol levels begin to fall rapidly as the follicle ruptures and transitions into the corpus luteum. At the point of ovulation, $E_2$ levels typically range between **200–400 pg/ml** or higher. A value of 150 pg/ml is significantly lower than the expected peak required for ovulation. 2. **Why other options are incorrect:** * **Follicular Phase:** In the early follicular phase, $E_2$ is low (<50 pg/ml). However, in the **late follicular phase** (pre-ovulatory), levels rise steadily. 150 pg/ml is a very common value seen during the mid-to-late follicular phase as the dominant follicle matures. * **Luteal Phase:** After ovulation, the corpus luteum secretes both progesterone and estrogen. This causes a second, broader mid-luteal peak of estradiol, typically ranging between **100–200 pg/ml**. Thus, 150 pg/ml is a highly characteristic value for the mid-luteal phase. **NEET-PG High-Yield Pearls:** * **Threshold for LH Surge:** For the LH surge to occur, estradiol must be maintained at $>200$ pg/ml for at least 48 hours. * **Two Peaks:** Remember the "M" shape of the estrogen curve—the first peak is pre-ovulatory (higher), and the second is mid-luteal (lower). * **Progesterone:** Always peaks only once, during the mid-luteal phase (Day 21).

Q: What is the role of human placental lactogen?

Growth of fetus. **Explanation:** **Human Placental Lactogen (hPL)**, also known as Human Chorionic Somatomammotropin (hCS), is a polypeptide hormone produced by the syncytiotrophoblast of the placenta. Its primary physiological role is to act as a **"metabolic orchestrator"** to ensure a continuous nutrient supply for the **growth of the fetus**. 1. **Why Option C is Correct:** hPL is structurally similar to Growth Hormone. It induces **maternal insulin resistance** and lipolysis. By decreasing maternal glucose utilization and increasing free fatty acids in the mother’s blood, it ensures that a steady stream of glucose (the primary fuel) is shunted across the placenta to the fetus, thereby promoting fetal growth. 2. **Why Options A & B are Incorrect:** While hPL has "lactogenic" properties and promotes maternal breast development (mammotropic effect) in preparation for lactation, it does **not** stimulate actual milk production (which is the role of Prolactin) nor is its primary role fetal breast development. 3. **Why Option D is Incorrect:** While hPL is an endocrine hormone, "endocrine regulation" is too vague. Its specific, high-yield function is the metabolic regulation of fetal nutrition. **High-Yield Clinical Pearls for NEET-PG:** * **Diabetogenic Effect:** hPL is the primary hormone responsible for the increased insulin requirement during pregnancy and is the chief culprit behind **Gestational Diabetes Mellitus (GDM)**. * **Correlation with Mass:** Serum levels of hPL are directly proportional to **placental mass**; low levels can indicate placental insufficiency. * **Peak Levels:** hPL levels rise progressively throughout pregnancy, reaching their peak in the **third trimester**.

Q: What hormone controls the mucosal lining of the fallopian tube secretion for ovum nutrition?

Progesterone. **Explanation:** The correct answer is **Progesterone**. The fallopian tube (oviduct) contains two main types of epithelial cells: ciliated cells and non-ciliated **peg cells**. While estrogen is responsible for the proliferation of the mucosa and increasing the number of cilia, **progesterone** is the primary hormone that stimulates the secretory activity of the peg cells. These secretions provide a nutrient-rich environment (containing glycogen, electrolytes, and amino acids) essential for the survival of the ovum and the nourishment of the zygote during its transit through the tube. **Why other options are incorrect:** * **LH (Luteinizing Hormone):** Its primary role is to trigger ovulation and maintain the corpus luteum; it does not directly regulate tubal secretions. * **FSH (Follicle Stimulating Hormone):** It stimulates the growth of ovarian follicles and the production of estrogen but has no direct effect on the fallopian tube mucosa. * **Estrogen:** Estrogen promotes the **ciliogenesis** (formation and activity of cilia) and increases the vascularity of the tubes. While it prepares the tube, it is progesterone that triggers the actual "secretory phase" of the tubal lining. **High-Yield NEET-PG Pearls:** * **Ciliary movement:** Estrogen increases the frequency of ciliary beating to facilitate gamete transport. * **Peg Cells:** These are non-ciliated, secretory cells that bulge into the lumen; their activity peaks in the post-ovulatory (luteal) phase under progesterone influence. * **Capacitation:** The secretions stimulated by progesterone also play a role in the final maturation of sperm (capacitation) within the female reproductive tract.

Q: Which of the following parameters is decreased during the third trimester of a normal pregnancy?

Systemic vascular resistance. **Explanation:** The correct answer is **Systemic Vascular Resistance (SVR)**. During pregnancy, the cardiovascular system undergoes significant remodeling to accommodate the metabolic demands of the fetus. **1. Why Systemic Vascular Resistance (SVR) decreases:** SVR begins to fall as early as the first trimester, reaching its nadir (lowest point) during the second and third trimesters (a 20–30% reduction). This occurs due to two primary mechanisms: * **Progesterone and Nitric Oxide:** High levels of progesterone and increased synthesis of nitric oxide and prostaglandins cause significant peripheral vasodilation. * **Uteroplacental Circulation:** The placenta acts as a large, **low-resistance shunt** added in parallel to the maternal circulation, further lowering the overall resistance. **2. Why the other options are incorrect:** * **Cardiac Output (CO):** CO **increases** by 30–50% during pregnancy. It peaks by the end of the second trimester and remains elevated through the third. * **Heart Rate (HR):** HR gradually **increases** throughout pregnancy, typically rising by 10–20 beats per minute above baseline. * **Stroke Volume (SV):** SV **increases** significantly, especially in early pregnancy, due to increased plasma volume and improved myocardial contractility. **High-Yield Facts for NEET-PG:** * **Blood Pressure:** Despite the increase in CO, Mean Arterial Pressure (MAP) **decreases** slightly because the drop in SVR is more profound. * **Plasma Volume:** Increases by ~50%, while RBC mass increases by ~20-30%, leading to **Physiological Anemia of Pregnancy**. * **Supine Hypotension Syndrome:** In the third trimester, the gravid uterus can compress the Inferior Vena Cava (IVC) when the mother lies supine, reducing venous return and CO. Always advise the **left lateral position**.

Q: Most of the testosterone secreted by the testes exists in the plasma in the form of?

Testosterone bound to sex-steroid-binding globulin. ### Explanation **1. Why the Correct Answer is Right:** Testosterone is a lipophilic steroid hormone that requires carrier proteins for transport in the aqueous environment of the plasma. In adult males, approximately **98% of circulating testosterone is protein-bound**. The majority (about **65-70%**) is bound with high affinity to **Sex-Steroid-Binding Globulin (SSBG)**, also known as Sex Hormone-Binding Globulin (SHBG). The remaining bound fraction (approx. 30%) is loosely attached to **Albumin**. Only the unbound or "free" fraction (approx. 2%) is biologically active and capable of entering target cells. **2. Why the Incorrect Options are Wrong:** * **Options A & B (Dihydrotestosterone):** While Dihydrotestosterone (DHT) is a more potent androgen, it is primarily formed in peripheral tissues (like the prostate and skin) by the action of the enzyme 5-alpha-reductase on testosterone. It is not the primary form in which testosterone itself exists in the plasma. * **Option C (Free Testosterone):** Only a very small fraction (about **2%**) of testosterone exists in the free, unbound state. While this fraction is physiologically the most important for hormonal action, it does not represent the "most" common form in the plasma. **3. High-Yield Clinical Pearls for NEET-PG:** * **Bioavailable Testosterone:** This refers to the sum of **Free Testosterone + Albumin-bound Testosterone**. Because the binding to albumin is weak/low-affinity, it dissociates easily for tissue uptake. * **SHBG Regulation:** SHBG levels are **increased** by Estrogen and Hyperthyroidism, and **decreased** by Androgens, Obesity, and Nephrotic syndrome. * **Origin:** Testosterone is secreted by the **Leydig cells** of the testes under the influence of **Luteinizing Hormone (LH)**.

Q: All of the following physiological changes occur in pregnancy EXCEPT?

Decrease in fibrinogen levels. **Explanation:** Pregnancy is a state of significant physiological adaptation across multiple organ systems to support the growing fetus. **Why Option C is the Correct Answer:** Pregnancy is a **hypercoagulable state**. There is a significant **increase** (not decrease) in the levels of most clotting factors, particularly **Fibrinogen (Factor I)**, which can rise by up to 50% (reaching 400–600 mg/dL). This serves as a protective mechanism to prevent postpartum hemorrhage. Other changes include a decrease in Protein S activity and an increase in Plasminogen Activator Inhibitor (PAI-1 and PAI-2), further increasing the risk of thromboembolism. **Analysis of Incorrect Options:** * **Option A & B:** Cardiac output (CO) increases by 30–50% during pregnancy. This is achieved by an **increase in Stroke Volume (SV)** (predominantly in the first half of pregnancy) and an **increase in Heart Rate (HR)** (predominantly in the second half). Since $CO = SV \times HR$, both options are physiological features of pregnancy. * **Option D:** In the supine position, the gravid uterus compresses the **Inferior Vena Cava (IVC)**. This mechanical obstruction leads to increased venous pressure in the lower limbs, often resulting in dependent edema and varicose veins. It can also lead to "Supine Hypotension Syndrome" due to decreased venous return. **High-Yield NEET-PG Pearls:** * **Hematology:** Plasma volume increases (50%) more than RBC mass (20–30%), leading to **physiological anemia**. * **Respiratory:** Tidal Volume increases (Progesterone effect), but **Functional Residual Capacity (FRC) decreases** due to the elevation of the diaphragm. * **Renal:** GFR and Renal Plasma Flow increase, leading to a **decrease in serum Creatinine and Urea** levels.

Q: What are the typical prolactin levels during pregnancy?

Highest during pregnancy. **Explanation:** **Why Option B is Correct:** During pregnancy, prolactin levels undergo a progressive and significant increase, reaching their peak (highest levels) during the third trimester. This rise is primarily driven by high levels of **estrogen** secreted by the placenta. Estrogen stimulates the lactotrophs in the anterior pituitary gland to undergo both hyperplasia (increase in cell number) and hypertrophy (increase in cell size). By the end of pregnancy, prolactin levels can be 10 to 20 times higher than non-pregnant levels (reaching up to 200 ng/mL), preparing the mammary glands for lactation. **Why Other Options are Incorrect:** * **Option A:** Prolactin is never at its lowest during pregnancy; in fact, it is one of the hormones that shows the most dramatic increase. * **Option C:** Prolactin is profoundly affected by both. Pregnancy increases its baseline level, while lactation (specifically the suckling reflex) causes episodic surges to maintain milk production. * **Option D:** While exact numerical values may vary slightly between individuals, the physiological trend of a steady, significant increase is a universal feature of normal human pregnancy. **High-Yield Clinical Pearls for NEET-PG:** * **The Estrogen Paradox:** Although prolactin levels are highest during pregnancy, milk secretion (lactation) does not occur *in utero*. This is because high levels of **estrogen and progesterone** competitively inhibit the action of prolactin on the breast tissue. Lactation only begins postpartum once these steroid levels plummet. * **Pituitary Size:** Due to lactotroph hyperplasia, the pituitary gland increases in size by nearly 50-100% during pregnancy, making it more susceptible to infarction if massive hemorrhage occurs (**Sheehan’s Syndrome**). * **Amniotic Fluid:** Prolactin is also found in high concentrations in amniotic fluid, where it helps regulate fetal osmoregulation.

Question 1

Which of the following is true during the 12-hour period preceding ovulation?

Accepted Answer

A surge of LH is secreted from the pituitary

Answer

The surge occurs immediately after the formation of the corpus luteum

Answer

The surge is followed immediately by a fall in the plasma concentration of progesterone

Answer

The number of developing follicles is increasing

Question 2

Which of the following statements is true regarding the timing of ovulation?

Accepted Answer

Ovulation occurs after follicular ripening by FSH.

Answer

Ovulation occurs before the LH surge.

Answer

Ovulation occurs after the biphasic rise in basal body temperature.

Answer

Ovulation occurs after the disappearance of cervical mucus thickening.

Question 3

Which of the following provides the environment for capacitation of sperm?

Accepted Answer

Male reproductive tract

Answer

Arteriole

Answer

Capillary

Answer

Vein

Question 4

A patient's blood estradiol level is measured at 150 pg/ml. In which phase of the menstrual cycle is the woman LEAST likely to be?

Accepted Answer

Ovulation phase

Answer

Follicular phase

Answer

Luteal phase

Answer

None of the above

Question 5

What is the role of human placental lactogen?

Accepted Answer

Growth of fetus

Answer

Stimulate milk production

Answer

Fetal breast development

Answer

Endocrine regulation

Question 6

What hormone controls the mucosal lining of the fallopian tube secretion for ovum nutrition?

Accepted Answer

Progesterone

Answer

LH

Answer

FSH

Answer

Estrogen

Question 7

Which of the following parameters is decreased during the third trimester of a normal pregnancy?

Accepted Answer

Systemic vascular resistance

Answer

Heart rate

Answer

Stroke volume

Answer

Cardiac output

Question 8

Most of the testosterone secreted by the testes exists in the plasma in the form of?

Accepted Answer

Testosterone bound to sex-steroid-binding globulin

Answer

Dihydrotestosterone bound to gonadal steroid-binding hormone

Answer

Free dihydrotestosterone

Answer

Free testosterone

Question 9

All of the following physiological changes occur in pregnancy EXCEPT?

Accepted Answer

Decrease in fibrinogen levels

Answer

Increase in cardiac output

Answer

Increase in stroke volume

Answer

Rise in the venous pressure in the lower limb in the supine position

Question 10

What are the typical prolactin levels during pregnancy?

Accepted Answer

Highest during pregnancy

Answer

Lowest during pregnancy

Answer

Unaffected by pregnancy and lactation

Answer

Variable in every pregnancy

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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