Reproductive Physiology Practice Questions

Q: Which of the following is NOT secreted by Sertoli cells?

Androgen. The key to answering this question lies in understanding the **Two-Cell, Two-Gonadotropin Theory** of the testes. ### Why Androgen is the Correct Answer **Androgens (specifically Testosterone)** are synthesized and secreted by the **Leydig cells** (interstitial cells) under the influence of Luteinizing Hormone (LH). Sertoli cells lack the enzyme **17β-hydroxysteroid dehydrogenase**, which is essential for the final step of testosterone synthesis. Therefore, Sertoli cells do not produce androgens; they are the *targets* of androgens. ### Why the Other Options are Incorrect * **Aromatase (B):** Sertoli cells contain the enzyme aromatase, which converts testosterone (diffusing from Leydig cells) into **estrogens**. This is a crucial function for local regulation. * **Inhibin (C):** Sertoli cells secrete **Inhibin B**, which provides negative feedback to the anterior pituitary to inhibit the secretion of Follicle-Stimulating Hormone (FSH). * **ABP (Androgen Binding Protein) (D):** Secreted by Sertoli cells in response to FSH, ABP binds to testosterone to maintain high local concentrations within the seminiferous tubules, which is essential for spermatogenesis. ### High-Yield NEET-PG Pearls * **Sertoli Cell Functions (Mnemonic: "B-A-I-T"):** **B**lood-testis barrier formation, **A**BP/Aromatase/AMH production, **I**nhibin secretion, and **T**rophic support for sperm. * **Anti-Müllerian Hormone (AMH):** Also secreted by Sertoli cells; it causes regression of Müllerian ducts in male fetuses. * **Blood-Testis Barrier:** Formed by **tight junctions** between adjacent Sertoli cells, protecting developing sperm from the immune system. * **Sertoli-only syndrome:** A condition where germ cells are absent, leading to infertility, but testosterone levels remain normal because Leydig cells are unaffected.

Q: Increased gonadal production of estrogen is characteristic of which of the following conditions?

Testicular feminization. **Explanation:** **Testicular Feminization (Androgen Insensitivity Syndrome - AIS)** is the correct answer. In this condition, there is a functional defect in androgen receptors. Because the body cannot respond to testosterone, the negative feedback loop to the hypothalamus and pituitary is disrupted. This leads to **increased LH secretion**, which chronically stimulates the Leydig cells of the testes. Consequently, the testes produce high levels of testosterone, much of which is peripherally converted into **estrogen** via the enzyme aromatase. This increased gonadal production of estrogen leads to female secondary sexual characteristics (e.g., breast development) in a genotypic male (46, XY). **Analysis of Incorrect Options:** * **Polycystic Ovarian Disease (PCOD):** While estrogen levels are often elevated, it is primarily due to the peripheral conversion of androstenedione (androgens) in adipose tissue, rather than direct increased gonadal production of estrogen. * **Congenital Adrenal Hyperplasia (CAH):** This condition typically involves a deficiency in enzymes like 21-hydroxylase, leading to a shunting of precursors toward **androgen** production. Estrogen levels are generally low or normal, not increased. * **Third Trimester of Pregnancy:** During pregnancy, the massive increase in estrogen is primarily produced by the **placenta** (using fetal adrenal precursors), not the maternal gonads (ovaries). **High-Yield Clinical Pearls for NEET-PG:** * **Karyotype in AIS:** 46, XY (Genotypic male, Phenotypic female). * **Key Finding:** Presence of undescended testes (often in the inguinal canal) and a blind-ending vagina with an absent uterus/fallopian tubes (due to normal MIS/AMH action). * **Biochemical Profile:** High Testosterone, High LH, and High Estrogen (relative to normal males).

Q: Which is the major hormone secreted by the corpus luteum in a woman of reproductive age?

Progesterone. ### Explanation **Correct Answer: B. Progesterone** The **corpus luteum** is a temporary endocrine structure formed from the remnants of the ovarian follicle after ovulation. Under the influence of Luteinizing Hormone (LH), the granulosa and theca cells undergo "luteinization." While the corpus luteum secretes both estrogen and progesterone, **progesterone** is the primary and most significant hormone produced. Its main physiological role is to prepare the endometrium for implantation (secretory phase) and maintain early pregnancy by inhibiting uterine contractions. **Analysis of Incorrect Options:** * **A. Estrogen:** Although the corpus luteum secretes 17β-estradiol, it is secondary to progesterone. Estrogen is the dominant hormone of the *follicular phase* (secreted by growing follicles), whereas progesterone dominates the *luteal phase*. * **C. Testosterone:** This is an androgen. While small amounts of androgens are produced by the ovarian theca cells as precursors to estrogen, they are not the major secretion of the corpus luteum. * **D. Thyroxine:** This is secreted by the thyroid gland and is involved in basal metabolic rate, not specifically by the ovarian structures. **High-Yield Clinical Pearls for NEET-PG:** * **Life Span:** In a non-pregnant cycle, the corpus luteum lasts for about **12–14 days** before degenerating into the *corpus albicans* due to a drop in LH. * **Pregnancy Maintenance:** If fertilization occurs, **hCG** (Human Chorionic Gonadotropin) rescues the corpus luteum, allowing it to produce progesterone until the **placenta** takes over (the luteal-placental shift) at approximately **7–9 weeks** of gestation. * **Inhibin B vs. A:** Remember that **Inhibin A** is the predominant form secreted by the corpus luteum, while Inhibin B is secreted by granulosa cells during the follicular phase.

Q: The production of cervical mucus is stimulated by which hormone?

Estradiol. **Explanation:** The characteristics and volume of cervical mucus are under direct hormonal control during the menstrual cycle. **1. Why Estradiol is Correct:** During the follicular phase, rising levels of **Estradiol (E2)** stimulate the endocervical glands to produce large quantities of mucus. Under estrogenic influence, the mucus becomes **profuse, watery, alkaline, and clear**. This environment is specifically designed to facilitate sperm transport and survival. High estradiol levels also cause the mucus to exhibit "ferning" (crystallization on a slide) and high "spinnbarkeit" (elasticity/stretchability), which are classic indicators of the periovulatory period. **2. Why the Other Options are Incorrect:** * **Progesterone:** This hormone dominates the luteal phase. It has an antagonistic effect on cervical mucus, making it **thick, viscid, cellular, and scanty**. This creates a "cervical plug" that is hostile to sperm penetration. * **Pregnenolone:** This is a precursor steroid in the biosynthetic pathway of adrenal and gonadal hormones. It does not have a direct physiological effect on the cervical epithelium. * **Estriol:** While an estrogen, it is a weak metabolite primarily significant during pregnancy (produced by the feto-placental unit). Estradiol is the potent, primary estrogen responsible for cyclical changes in the non-pregnant reproductive tract. **High-Yield Clinical Pearls for NEET-PG:** * **Spinnbarkeit Test:** Measures the elasticity of cervical mucus; maximum elasticity (>10 cm) occurs just before ovulation due to peak Estradiol. * **Ferning Pattern:** Caused by increased sodium chloride concentration in mucus under estrogen influence. Progesterone inhibits this pattern. * **Auscultation of Ovulation:** The transition from watery (Estrogen) to thick (Progesterone) mucus is a reliable retrospective indicator that ovulation has occurred.

Q: Menopausal hot flushes coincide with which of the following?

LH surge. **Explanation:** The correct answer is **LH surge**. **Underlying Medical Concept:** Menopausal hot flushes (vasomotor symptoms) are caused by the narrowing of the thermoregulatory set-point in the hypothalamus. In menopause, the lack of negative feedback from estrogen leads to an increase in **Gonadotropin-Releasing Hormone (GnRH)** pulses. These GnRH pulses stimulate the pituitary to release **Luteinizing Hormone (LH)**. Clinical studies have shown that each episode of a hot flush coincides precisely with a **pulsatile surge of LH**. It is important to note that while the LH surge is the marker, the LH itself is not the cause; rather, the same hypothalamic signals (GnRH and neurokinin B) that trigger the LH pulse also trigger the thermoregulatory dysfunction in the adjacent preoptic nucleus of the hypothalamus. **Analysis of Incorrect Options:** * **A. FSH secretion:** While FSH levels are chronically elevated in menopause (the most sensitive marker), its secretion does not show the same temporal synchronization with individual hot flush episodes as LH. * **B. Decrease in estrogen:** Low estrogen is the *ultimate cause* of menopause, but hot flushes occur in discrete episodes. Estrogen levels do not drop further during the actual flush. * **C. Increase in progesterone:** Progesterone levels are consistently low in menopause due to the absence of ovulation and the corpus luteum. **High-Yield Facts for NEET-PG:** * **Most sensitive marker for Menopause:** Elevated FSH (>40 mIU/ml). * **KNDy Neurons:** Neurons in the hypothalamus (expressing Kisspeptin, Neurokinin B, and Dynorphin) are now considered the "central thermostat" involved in hot flushes. * **Drug of Choice:** Hormone Replacement Therapy (HRT) is the most effective treatment; **SSRIs/SNRIs** or **Gabapentin** are non-hormonal alternatives. * **Fezolinetant:** A newer NK3 receptor antagonist specifically targeting the mechanism of hot flushes.

Q: What is the primary fuel source for sperm motility?

Fructose. **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.

Q: Sperm becomes mobile in which of the following locations?

Epididymis. **Explanation:** The correct answer is **Epididymis**. While spermatogenesis (the production of sperm) occurs in the seminiferous tubules of the **testis**, the sperm produced there are morphologically complete but physiologically immature and non-motile [1]. **Why Epididymis is correct:** As sperm pass through the head, body, and tail of the epididymis (a process taking about 12–14 days), they undergo **physiological maturation**. During this transit, they acquire forward progressive motility and the ability to fertilize an ovum [1]. This is primarily due to changes in the plasma membrane and the acquisition of proteins that enable flagellar movement. **Analysis of Incorrect Options:** * **Testis:** Sperm in the testis are immotile [1]. They are transported to the epididymis via bulk fluid flow and ciliary action of the efferent ductules. * **Vas deferens:** This serves primarily as a storage site (in the ampulla) and a conduit for sperm transport during ejaculation. It does not initiate motility. * **Prostatic urethra:** This is a passage for semen during ejaculation where sperm mix with prostatic and seminal vesicle secretions. While these secretions provide nutrients and alkaline buffering, the capacity for motility was already acquired in the epididymis. **High-Yield NEET-PG Pearls:** * **Decapacitation:** In the epididymis, "decapacitation factors" are added to the sperm surface to prevent them from undergoing the acrosome reaction prematurely. * **Capacitation:** This is the final step of maturation where sperm gain "hyperactivated motility." Crucially, this occurs in the **female reproductive tract** (specifically the isthmus of the fallopian tube), not the male tract. * **Storage:** The tail (cauda) of the epididymis is the primary site for sperm storage before ejaculation.

Q: Which of the following physiological changes occurs during pregnancy?

Decreased residual volume. **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).

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

May cause respiratory distress syndrome. **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 1

Which of the following is NOT secreted by Sertoli cells?

Accepted Answer

Androgen

Answer

Aromatase

Answer

Inhibin

Answer

ABP

Question 2

Increased gonadal production of estrogen is characteristic of which of the following conditions?

Accepted Answer

Testicular feminization

Answer

Polycystic ovarian disease

Answer

Congenital adrenal hyperplasia

Answer

Third trimester of pregnancy

Question 3

Which is the major hormone secreted by the corpus luteum in a woman of reproductive age?

Accepted Answer

Progesterone

Answer

Estrogen

Answer

Testosterone

Answer

Thyroxine

Question 4

The production of cervical mucus is stimulated by which hormone?

Accepted Answer

Estradiol

Answer

Progesterone

Answer

Pregnenolone

Answer

Estriol

Question 5

Menopausal hot flushes coincide with which of the following?

Accepted Answer

LH surge

Answer

FSH secretion

Answer

Decrease in estrogen

Answer

Increase in progesterone

Question 6

What is the primary fuel source for sperm motility?

Accepted Answer

Fructose

Answer

Glucose

Answer

Fatty acids

Answer

Prostatic acid phosphatase

Question 7

Sperm becomes mobile in which of the following locations?

Accepted Answer

Epididymis

Answer

Vas deferens

Answer

Prostatic urethra

Answer

Testis

Question 8

How is immune rejection in the fetus prevented?

Accepted Answer

HCG

Answer

HPL

Answer

Oestrogen

Answer

Progesterone

Question 9

Which of the following physiological changes occurs during pregnancy?

Accepted Answer

Decreased residual volume

Answer

Decreased GFR

Answer

Decreased Cardiac output

Answer

Increased Haematocrit

Question 10

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

Accepted Answer

May cause respiratory distress syndrome

Answer

Causes aspiration of amniotic fluid

Answer

Increase towards term

Answer

Help in conditioning of respiratory muscles

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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