Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 251: All of the following are true about regional blood flow in pregnancy except?

A. Uterine blood flow at term is 750 ml/min.
B. Blood flow through the skin decreases. (Correct Answer)
C. Renal blood flow increases by 50%.
D. Pulmonary blood flow increases.

Explanation: In pregnancy, the maternal cardiovascular system undergoes significant adaptation to meet the metabolic demands of the fetus and the mother. **Explanation of the Correct Answer (Option B):** Contrary to the statement, **skin blood flow actually increases** significantly during pregnancy. This is a physiological mechanism for **thermoregulation**. The increased metabolic rate of the fetus and mother generates excess heat; to dissipate this, peripheral vasodilation occurs, leading to increased blood flow to the skin (especially in the hands and feet). This often manifests clinically as "pregnancy glow," palmar erythema, or a feeling of heat intolerance. **Analysis of Incorrect Options:** * **Option A:** Uterine blood flow increases dramatically from ~50 ml/min in the non-pregnant state to **750–900 ml/min at term**. This ensures adequate nutrient and oxygen delivery to the placenta. * **Option C:** Renal blood flow (RBF) increases by approximately **50%** as early as the first trimester. This is due to systemic vasodilation and increased cardiac output, leading to a subsequent rise in the Glomerular Filtration Rate (GFR). * **Option D:** Pulmonary blood flow increases because it is equal to the **Cardiac Output**, which rises by 30–50% during pregnancy to accommodate the increased stroke volume and heart rate. **NEET-PG High-Yield Pearls:** * **Cardiac Output:** Peaks at 20–24 weeks of gestation. * **Blood Volume:** Increases by 40–50%, but plasma volume increases more than RBC mass, leading to **physiological anemia**. * **Blood Pressure:** Systemic vascular resistance (SVR) decreases, causing a **nadir in BP during the second trimester**. * **Organ flow that does NOT change:** Brain and Liver blood flow remain constant during pregnancy.

Question 252: What is the primary fuel source for sperm motility?

A. Glucose
B. Fructose (Correct Answer)
C. Fatty acids
D. Prostatic acid phosphatase

Explanation: **Explanation:** The primary fuel source for sperm motility is **Fructose**. Spermatozoa require a significant amount of energy (ATP) to power the flagellar movement (dynein ATPase activity) necessary for transit through the female reproductive tract. 1. **Why Fructose is Correct:** Fructose is secreted in high concentrations by the **seminal vesicles** (contributing ~60% of semen volume). Sperm cells utilize fructose through anaerobic glycolysis and oxidative phosphorylation to generate ATP. Fructose is preferred over glucose in semen because it is specifically secreted for this purpose and provides a ready energy source that does not compete with the glucose requirements of other body tissues. 2. **Why Incorrect Options are Wrong:** * **Glucose:** While sperm *can* metabolize glucose, it is not the primary sugar found in seminal fluid. * **Fatty acids:** These are a major energy source for cardiac and skeletal muscle but are not the primary substrate for sperm motility in the ejaculate. * **Prostatic acid phosphatase:** This is an enzyme secreted by the prostate gland used as a marker for prostatic function and forensic analysis of semen; it has no role as a fuel source. **High-Yield NEET-PG Pearls:** * **Source:** Fructose is produced by the seminal vesicles under the influence of **androgens**. * **Clinical Correlation:** The absence of fructose in a semen sample (fructose-negative) suggests **bilateral congenital absence of the vas deferens (CBAVD)** or seminal vesicle obstruction. * **Semen pH:** Seminal vesicle fluid is alkaline, which helps neutralize the acidic environment of the vagina.

Question 253: Which of the following physiological changes occurs during pregnancy?

A. Decreased residual volume (Correct Answer)
B. Decreased GFR
C. Decreased Cardiac output
D. Increased Haematocrit

Explanation: **Explanation:** During pregnancy, the body undergoes significant physiological adaptations to support the growing fetus. **1. Why Option A is Correct:** The primary reason for **decreased Residual Volume (RV)** is the anatomical change caused by the enlarging uterus. As the uterus grows, it pushes the diaphragm upward by approximately 4 cm. This elevation reduces the space in the thoracic cavity at the end of expiration, leading to a decrease in RV (by ~20%) and Functional Residual Capacity (FRC). Despite this, the Vital Capacity remains unchanged because the transverse diameter of the chest increases to compensate. **2. Why the other options are incorrect:** * **B. Decreased GFR:** This is incorrect. Renal blood flow and **Glomerular Filtration Rate (GFR) actually increase** by 40-50% due to vasodilation and increased cardiac output. This leads to lower baseline serum creatinine and urea levels in pregnant women. * **C. Decreased Cardiac Output:** This is incorrect. **Cardiac output increases** by 30-50% to meet metabolic demands. This is achieved through increases in both stroke volume (early pregnancy) and heart rate (late pregnancy). * **D. Increased Haematocrit:** This is incorrect. While red cell mass increases, the plasma volume increases disproportionately more (approx. 50% vs 20%). This results in hemodilution, leading to a **decreased haematocrit**, a condition known as **Physiological Anemia of Pregnancy**. **High-Yield Clinical Pearls for NEET-PG:** * **Most common respiratory change:** Increased Tidal Volume (leads to physiological hyperventilation and respiratory alkalosis). * **Most common cardiovascular change:** Increased Cardiac Output (peaks at 20-24 weeks). * **Coagulation:** Pregnancy is a **hypercoagulable state** (increase in Factors VII, VIII, IX, X, and Fibrinogen; decrease in Protein S).

Question 254: With respect to fetal breathing movements, which of the following statements is not true?

A. May cause respiratory distress syndrome (Correct Answer)
B. Causes aspiration of amniotic fluid
C. Increase towards term
D. Help in conditioning of respiratory muscles

Explanation: **Explanation:** Fetal breathing movements (FBMs) are episodic, irregular movements of the chest wall and diaphragm that begin as early as the first trimester (around 10–12 weeks). **Why Option A is the Correct Answer (The False Statement):** Fetal breathing movements do **not** cause Respiratory Distress Syndrome (RDS). RDS is primarily caused by a **deficiency of surfactant** in premature infants, leading to alveolar collapse. In fact, FBMs are essential for normal lung development; they stimulate the release of surfactant into the amniotic fluid and promote the growth of alveolar structures. **Analysis of Incorrect Options (True Statements):** * **Option B:** FBMs cause the inward and outward movement of amniotic fluid. While the volume is small, this "aspiration" is crucial for providing the mechanical stretch required for lung expansion and maturation. * **Option C:** The frequency and intensity of FBMs increase as the fetus approaches term. However, they typically decrease or disappear 24–48 hours before the onset of true labor (likely due to increased prostaglandin levels). * **Option D:** FBMs serve as a vital "workout" for the diaphragm and intercostal muscles, conditioning them so they are strong enough to sustain continuous breathing immediately after birth. **High-Yield Clinical Pearls for NEET-PG:** * **Regulation:** FBMs occur primarily during **REM (Rapid Eye Movement) sleep** and are inhibited by hypoxia and hypoglycemia. * **Biophysical Profile (BPP):** FBM is one of the five components of the Manning’s BPP. A normal score requires at least one episode of FBM lasting $\geq$ 30 seconds within a 30-minute window. * **Diagnostic Value:** The presence of FBMs is a reassuring sign of fetal well-being and an intact central nervous system.

Question 255: Which hormone is required for late-stage development of antral follicles?

A. Androstenedione
B. FSH (Correct Answer)
C. LH
D. Estradiol

Explanation: **Explanation:** The development of ovarian follicles occurs in two distinct phases: the gonadotropin-independent phase and the **gonadotropin-dependent phase**. While early follicular growth (up to the pre-antral stage) is regulated by local growth factors, the transition to and maturation of the **antral follicle** (late-stage development) is strictly dependent on **Follicle-Stimulating Hormone (FSH)**. FSH binds to receptors on granulosa cells, stimulating their proliferation and the expression of the aromatase enzyme. This process is essential for the formation of the antrum (fluid-filled cavity) and the selection of the dominant follicle. Without FSH, antral follicles undergo atresia. **Analysis of Incorrect Options:** * **Androstenedione (A):** This is an androgen precursor produced by theca cells under LH influence. While it serves as a substrate for estrogen synthesis, high levels can actually promote follicular atresia rather than development. * **LH (C):** LH primarily acts on theca cells to produce androgens. While LH is crucial for the final maturation of the *dominant* follicle and triggers ovulation, FSH is the primary driver for the general development of the antral cohort. * **Estradiol (D):** Estradiol is a product of follicular development (via the Two-Cell, Two-Gonadotropin theory). While it exerts positive feedback on the granulosa cells, it is not the primary hormone "required" to initiate or sustain late-stage antral growth. **High-Yield Clinical Pearls for NEET-PG:** * **Two-Cell, Two-Gonadotropin Theory:** LH stimulates **Theca cells** (produce Androgens); FSH stimulates **Granulosa cells** (convert Androgens to Estrogens via Aromatase). * **FSH Window:** The period during the early follicular phase when FSH levels rise above a threshold to "rescue" a cohort of antral follicles from apoptosis. * **LH Surge:** Occurs 24–36 hours before ovulation; it is the reliable predictor of the mid-cycle surge.

Question 256: Which of the following is NOT an effect of estrogen?

A. Reduces HDL (Correct Answer)
B. Reduces LDL
C. Increases triglyceride
D. Reduces bone resorption

Explanation: Estrogen exerts significant effects on lipid metabolism and bone density, which are crucial for understanding cardiovascular and skeletal health in women. **Explanation of the Correct Answer:** **Option A (Reduces HDL)** is the correct answer because it is a **false statement**. Estrogen actually **increases HDL** (High-Density Lipoprotein), the "good cholesterol." It does this by increasing the synthesis of Apolipoprotein A-I and decreasing the activity of hepatic lipase, which slows the degradation of HDL particles. This cardioprotective effect explains why premenopausal women have a lower risk of atherosclerosis compared to men of the same age. **Explanation of Incorrect Options:** * **Option B (Reduces LDL):** Estrogen **decreases LDL** (the "bad cholesterol") by increasing the expression of LDL receptors in the liver, leading to enhanced clearance of LDL from the blood. * **Option C (Increases triglyceride):** Estrogen **increases plasma triglycerides** by stimulating the production of VLDL (Very Low-Density Lipoprotein) in the liver. This is a known side effect of oral estrogen therapy. * **Option D (Reduces bone resorption):** Estrogen is vital for bone health. It inhibits osteoclast activity (by increasing OPG and decreasing RANKL) and promotes osteoclast apoptosis, thereby **reducing bone resorption**. This is why estrogen deficiency in menopause leads to osteoporosis. **High-Yield Facts for NEET-PG:** * **Lipid Profile:** Estrogen = ↑ HDL, ↓ LDL, ↑ Triglycerides. * **Bone:** Estrogen maintains bone density by inhibiting **Interleukin-6 (IL-6)**, a potent stimulator of osteoclasts. * **Coagulation:** Estrogen increases the synthesis of clotting factors (II, VII, IX, X) and decreases Antithrombin III, explaining the pro-thrombotic risk of OCPs.

Question 257: Mullerian inhibiting substance in utero is secreted by?

A. Leydig cells
B. Sertoli cells (Correct Answer)
C. Granulosa cells
D. Theca cells

Explanation: **Explanation:** The development of the male reproductive system in utero is an active process driven by two key hormones secreted by the fetal testes. **Mullerian Inhibiting Substance (MIS)**, also known as Anti-Müllerian Hormone (AMH), is a glycoprotein secreted by the **Sertoli cells**. Its primary function is to cause the regression of the Müllerian (paramesonephric) ducts, which would otherwise develop into the uterus, fallopian tubes, and upper vagina. * **Option A (Leydig cells):** These cells secrete **Testosterone**. Testosterone is responsible for the stabilization and development of the Wolffian (mesonephric) ducts into the epididymis, vas deferens, and seminal vesicles. It does not cause Müllerian duct regression. * **Option C & D (Granulosa & Theca cells):** These are ovarian cells. In a female fetus, the absence of Sertoli cells means no MIS is produced, allowing the Müllerian ducts to develop by default. While Granulosa cells produce AMH later in life (used as a marker for ovarian reserve), they are not the source of MIS for ductal differentiation in utero. **High-Yield Clinical Pearls for NEET-PG:** * **Persistent Müllerian Duct Syndrome:** Occurs due to a deficiency of MIS or a mutation in its receptor. The individual is a phenotypic male (46,XY) but possesses a uterus and fallopian tubes. * **Sry Gene:** Located on the Y chromosome, it triggers the undifferentiated gonad to become a testis. * **Dihydrotestosterone (DHT):** Produced from testosterone via 5-alpha reductase; it is responsible for the development of male external genitalia (penis and scrotum) and the prostate.

Question 258: Which of the following is responsible for pubertal growth in females?

A. Decreased level of adrenal androgens at puberty
B. High level of estrogen at puberty
C. Pulsatile release of GnRH during sleep (Correct Answer)
D. Increased sensitivity of the HPO axis to estrogen

Explanation: ### Explanation **Correct Option: C. Pulsatile release of GnRH during sleep** The initiation of puberty (pubertal growth and development) is fundamentally driven by the **"reawakening" of the GnRH pulse generator** in the hypothalamus. During childhood, the Hypothalamic-Pituitary-Ovarian (HPO) axis is quiescent. The hallmark of the onset of puberty is the nocturnal, **pulsatile secretion of Gonadotropin-Releasing Hormone (GnRH)** during sleep. This pulsatility triggers the pituitary to release LH and FSH, which subsequently stimulate the ovaries to produce estrogen, leading to the development of secondary sexual characteristics and the pubertal growth spurt. **Analysis of Incorrect Options:** * **A. Decreased level of adrenal androgens:** This is incorrect. Adrenarche (the increase in adrenal androgens like DHEA) actually occurs around age 6–8 and contributes to the growth of pubic and axillary hair, not a decrease. * **B. High level of estrogen:** While estrogen is responsible for physical changes (thelarche), it is a *result* of the HPO axis activation, not the primary trigger responsible for initiating the process. * **D. Increased sensitivity of the HPO axis:** This is the opposite of what occurs. Before puberty, the hypothalamus is **exquisitely sensitive** to even tiny amounts of estrogen (negative feedback). Puberty begins when this sensitivity **decreases** (the "Gonadostat" theory), allowing GnRH levels to rise despite circulating steroids. **High-Yield NEET-PG Pearls:** * **First sign of puberty in females:** Thelarche (breast budding), followed by Pubarche, then Menarche. * **First sign of puberty in males:** Increase in testicular volume (>4 ml). * **Leptin Connection:** Adequate body fat and leptin levels are required to "permit" the pulsatile release of GnRH. * **Precocious Puberty:** Defined as the appearance of secondary sexual characteristics before age 8 in girls and age 9 in boys.

Question 259: Development of granules in the follicles prior to ovulation is dependent on which hormone?

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

Explanation: **Explanation:** The correct answer is **LH (Luteinizing Hormone)**. **Why LH is Correct:** The development of **follicular granules** (specifically the luteinization of granulosa cells) is a hallmark of the pre-ovulatory phase. While FSH is responsible for the initial growth of follicles and the proliferation of granulosa cells, the final maturation and the "granulation" or luteinization process—where cells accumulate lipid droplets and yellow pigment (lutein)—is triggered by the **LH surge**. This process prepares the follicle for ovulation and the subsequent formation of the corpus luteum. **Why Other Options are Incorrect:** * **FSH (Follicle Stimulating Hormone):** FSH is essential for the recruitment of follicles and the development of the antrum. However, it does not drive the specific "granulation" or luteinization process that occurs just prior to ovulation. * **Estrogen:** Estrogen is produced by the granulosa cells under the influence of FSH. While it exerts positive feedback to trigger the LH surge, it is a product of follicular activity rather than the primary hormone driving pre-ovulatory granulation. * **Progesterone:** Progesterone levels only begin to rise significantly *after* the LH surge has initiated luteinization. It is the primary hormone of the secretory phase, not the driver of pre-ovulatory follicular changes. **High-Yield NEET-PG Pearls:** * **Two-Cell, Two-Gonadotropin Theory:** LH acts on **Theca cells** to produce androgens (androstenedione); FSH acts on **Granulosa cells** to convert these androgens into estrogens via the enzyme *aromatase*. * **LH Surge:** Occurs approximately 24–36 hours before ovulation. It is the reliable predictor of ovulation used in home kits. * **Meiosis I:** The LH surge is also responsible for the completion of Meiosis I in the primary oocyte, arresting it again in Metaphase of Meiosis II.

Question 260: True about the proliferative phase of the endometrium is:

A. It starts and proceeds rapidly for 3-5 days
B. The glands of the functional layer are simple tubules with regular epithelium
C. Intense hyperemia
D. All of the above (Correct Answer)

Explanation: The **Proliferative Phase** (also known as the Estrogenic or Follicular phase) occurs under the influence of estrogen secreted by the developing ovarian follicles. It typically lasts from day 5 to day 14 of the menstrual cycle. **Explanation of Options:** * **Option A (Timing):** Following menstruation, the endometrium is thin. Re-epithelialization begins as early as day 4-5. The proliferation proceeds rapidly, increasing the endometrial thickness from roughly 1 mm to 3-5 mm by the time of ovulation. * **Option B (Morphology):** During this phase, the endometrial glands are **simple, straight tubules** lined by a regular, columnar epithelium. They do not show the tortuosity or secretory activity (vacuoles) characteristic of the later secretory phase. * **Option C (Vascularity):** Estrogen promotes significant angiogenesis. There is **intense hyperemia** (increased blood flow) and stromal proliferation to support the growing tissue, preparing it for potential implantation. Since all three statements accurately describe the physiological changes during this phase, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Dominant Hormone:** Estrogen (specifically Estradiol). * **Histological Hallmark:** Presence of **mitotic figures** in both the glandular epithelium and the stroma. * **Comparison:** In the **Secretory Phase** (Progesterone-dominant), glands become "corkscrew" shaped or serrated, and sub-nucleolar vacuoles appear. * **Clinical Correlation:** Anovulatory cycles result in a persistent proliferative phase (due to lack of progesterone), which can lead to endometrial hyperplasia.

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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