Reproductive Physiology Practice Questions

Q: All of the following statements regarding Sertoli cells are TRUE, EXCEPT:

Stimulated by FSH. **Explanation:** The question asks for the **FALSE** statement regarding Sertoli cells. However, the provided key indicates "Stimulated by FSH" as the correct answer, which is a **factual error** in the question's premise. In standard physiology, Sertoli cells **are** stimulated by FSH. To provide a correct educational explanation based on medical facts, we must clarify the role of Sertoli cells. **1. Why the provided "Correct Answer" (C) is technically TRUE (and thus the question is likely flawed):** Sertoli cells possess specific receptors for **Follicle Stimulating Hormone (FSH)**. FSH binding triggers the synthesis of proteins necessary for spermatogenesis. Therefore, statement C is a true physiological fact. **2. Analysis of Other Options (All are TRUE statements):** * **Option A (Secretes Inhibin):** Sertoli cells secrete Inhibin B, which provides negative feedback to the anterior pituitary to inhibit FSH secretion. * **Option B (Secretes Androgen Binding Protein - ABP):** Sertoli cells produce ABP, which binds to testosterone, maintaining the high local concentrations required for sperm maturation within the seminiferous tubules. * **Option D (Forms Blood-Testis Barrier):** Adjacent Sertoli cells are joined by **tight junctions**, forming the blood-testis barrier. This protects developing haploid germ cells from the immune system and creates a specialized chemical environment. **Clinical Pearls for NEET-PG:** * **Mnemonic:** **S**ertoli cells = **S**upport / **S**permatogenesis / **S**timulated by F**S**H. * **Leydig cells** are stimulated by **LH** (L for L) and secrete Testosterone. * Sertoli cells also secrete **Anti-Müllerian Hormone (AMH)** during fetal development to regress Müllerian ducts. * They are often called "Nurse Cells" because they provide structural and nutritional support to developing sperm.

Q: Sertoli cells play a key role in which of the following processes?

Spermiogenesis. **Explanation:** **Sertoli cells** (also known as "nurse cells") are essential for the structural and metabolic support of developing sperm. **1. Why Spermiogenesis is Correct:** Spermiogenesis is the final stage of spermatogenesis where round **spermatids** transform into mature, motile **spermatozoa**. This process occurs while the spermatids are embedded in the deep cytoplasmic folds of Sertoli cells. Sertoli cells provide the necessary nutrients, phagocytose the discarded residual bodies (excess cytoplasm), and regulate the remodeling required for the sperm to acquire its characteristic shape. **2. Why the other options are incorrect:** * **B. Testosterone secretion:** This is the primary function of **Leydig cells** (interstitial cells), located in the connective tissue between seminiferous tubules, under the influence of LH. * **C. Secretion of seminal fluid:** The bulk of seminal fluid is produced by the **accessory glands** (Seminal vesicles ~60%, Prostate ~30%, and Bulbourethral glands). Sertoli cells only secrete a small amount of fluid into the seminiferous tubule lumen to transport sperm. * **D. Production of germ cells:** Germ cells (Spermatogonia) are derived from **primordial germ cells** that migrate to the gonadal ridge during embryogenesis. Sertoli cells support these cells but do not produce them. **High-Yield Clinical Pearls for NEET-PG:** * **Blood-Testis Barrier:** Formed by **tight junctions** between adjacent Sertoli cells; it protects immunologically distinct sperm from the host immune system. * **Hormonal Secretions:** Sertoli cells secrete **Inhibin B** (inhibits FSH), **Androgen Binding Protein (ABP)** (maintains high local testosterone), and **Anti-Müllerian Hormone (AMH)** (causes regression of Müllerian ducts in male fetuses). * **Regulation:** Sertoli cells are primarily stimulated by **FSH**.

Q: Which of the following hormones is responsible for inhibiting lactation during pregnancy?

Progesterone. **Explanation:** The correct answer is **Progesterone**. During pregnancy, high levels of estrogen and progesterone are essential for the structural development of the mammary glands (lobuloalveolar growth). However, **Progesterone** specifically exerts a potent inhibitory effect on the action of Prolactin at the mammary receptor level. It prevents the actual synthesis and secretion of milk (lactogenesis) while the fetus is still in utero. Once the placenta is delivered, progesterone levels plummet, lifting this inhibition and allowing Prolactin to initiate lactation. **Analysis of Incorrect Options:** * **Human Placental Lactogen (hPL):** Also known as Human Chorionic Somatomammotropin (hCS), it supports breast development and has weak lactogenic properties, but its primary role is metabolic (anti-insulin effect to ensure glucose supply to the fetus). * **Oxytocin:** This hormone is responsible for the **milk-ejection reflex** (let-down reflex) by causing contraction of myoepithelial cells. It does not inhibit lactation. * **Prolactin:** This is the primary hormone responsible for **milk production** (galactopoiesis). While its levels are high during pregnancy, its effect is masked by progesterone. **High-Yield Clinical Pearls for NEET-PG:** * **Estrogen** is primarily responsible for ductal growth, while **Progesterone** is responsible for alveolar development. * The sudden drop in **Progesterone** post-delivery is the physiological trigger for **Lactogenesis II** (copious milk production). * **Suckling** is the most important stimulus for maintaining Prolactin and Oxytocin secretion. * **Dopamine** acts as the Prolactin-Inhibiting Hormone (PIH); hence, dopamine agonists (e.g., Cabergoline) are used to suppress lactation clinically.

Q: Maximum function of the corpus luteum occurs when?

8-9 days after ovulation. ### Explanation The **corpus luteum** is a temporary endocrine structure formed from the remnants of the ovarian follicle after ovulation. Its primary function is the secretion of **progesterone** and estrogen to prepare the endometrium for potential implantation. **Why Option D is Correct:** Following ovulation (typically Day 14 of a 28-day cycle), the corpus luteum undergoes a period of rapid vascularization and hypertrophy. It reaches its **maximum size and functional peak** (highest progesterone secretion) approximately **8 to 9 days after ovulation** (around Day 22–23 of the menstrual cycle). If fertilization does not occur, the corpus luteum begins to regress (luteolysis) approximately 10–12 days after ovulation, eventually becoming the fibrotic *corpus albicans*. **Why Other Options are Incorrect:** * **A & B:** At or before ovulation, the follicle is still under the influence of FSH and LH to release the oocyte. The corpus luteum has not yet formed; therefore, it cannot function at this stage. * **C:** Three days after ovulation, the corpus luteum is still in its early formative stage (luteinization) and has not yet reached its peak secretory capacity or vascular maturity. **High-Yield NEET-PG Pearls:** * **Life Span:** The life span of the corpus luteum in a non-pregnant cycle is fixed at approximately **14 days**. * **Hormonal Support:** The corpus luteum is maintained by **LH** (Luteinizing Hormone) in a non-pregnant cycle and by **hCG** (human Chorionic Gonadotropin) if pregnancy occurs. * **Progesterone:** It is the "hormone of pregnancy." A serum progesterone level measured on Day 21 (mid-luteal phase) is the gold standard for confirming that ovulation has occurred. * **Inhibin B vs. A:** Inhibin B is high in the follicular phase, while **Inhibin A** peaks in the luteal phase (secreted by the corpus luteum).

Q: Which of the following statements regarding Anti-Müllerian hormone is false?

AMH is secreted by Leydig cells.. ### Explanation **Why Option D is the Correct Answer (The False Statement):** Anti-Müllerian Hormone (AMH), also known as Müllerian Inhibiting Substance (MIS), is a glycoprotein member of the TGF-β superfamily. In males, it is secreted by the **Sertoli cells** of the fetal testes, not the Leydig cells. Leydig cells are responsible for secreting Testosterone, which stabilizes the Wolffian ducts. **Analysis of Other Options:** * **Option A:** AMH acts locally via paracrine signaling to cause the apoptosis and regression of the **ipsilateral Müllerian duct** (which would otherwise form the uterus, fallopian tubes, and upper vagina). * **Option B:** AMH plays a crucial role in the first phase of testicular descent. It stimulates the growth of the **gubernaculum**, facilitating the **transabdominal descent** of the testes to the inguinal ring. (The second phase, transinguinal descent, is androgen-dependent). * **Option C:** In females, AMH is produced by the granulosa cells of pre-antral and small antral follicles. Because its levels remain relatively constant throughout the menstrual cycle and correlate with the number of primordial follicles, it is the gold-standard biochemical marker for **ovarian reserve**. **High-Yield Clinical Pearls for NEET-PG:** * **Persistent Müllerian Duct Syndrome (PMDS):** Occurs due to a deficiency of AMH or a mutation in its receptor. Clinical presentation: A genetic male (46,XY) with normal external genitalia but possessing a uterus and fallopian tubes, often associated with cryptorchidism. * **Sertoli Cells:** Secretes AMH and Inhibin B. * **Leydig Cells:** Secretes Testosterone (stimulated by LH). * **Clinical Use:** AMH levels are used to predict response to controlled ovarian stimulation in IVF and to diagnose Polycystic Ovary Syndrome (PCOS), where levels are typically elevated.

Q: Which of the following is NOT secreted by the placenta?

Prolactin. **Explanation:** The placenta acts as a sophisticated transient endocrine organ, but it does not produce all pregnancy-related hormones. **Why Prolactin is the correct answer:** While prolactin levels rise significantly during pregnancy, the hormone is **not** secreted by the placenta. It is primarily secreted by the **lactotrophs of the anterior pituitary gland**. Additionally, the uterine decidua (maternal side) produces prolactin to help regulate amniotic fluid water and electrolytes, but the placental tissue itself does not synthesize it. **Analysis of Incorrect Options:** * **Human Placental Lactogen (HPL):** Also known as Human Chorionic Somatomammotropin (hCS), it is synthesized by the syncytiotrophoblast. It acts as an insulin antagonist, ensuring a steady glucose supply to the fetus. * **Human Chorionic Gonadotropin (HCG):** Produced by the syncytiotrophoblast shortly after implantation. Its primary role is to rescue and maintain the corpus luteum to ensure continued progesterone production in early pregnancy. * **Progesterone:** Initially produced by the corpus luteum, the placenta takes over progesterone production around the 7th–9th week of gestation (the "luteal-placental shift"). It is essential for maintaining uterine quiescence. **NEET-PG High-Yield Pearls:** 1. **The Syncytiotrophoblast** is the functional endocrine unit of the placenta responsible for HCG, HPL, Estrogen, and Progesterone. 2. **HCG Levels:** Peak at approximately **10 weeks** of gestation and then decline. 3. **HPL Levels:** Increase progressively throughout pregnancy, correlating with placental mass. 4. **Estrogen in Pregnancy:** The placenta cannot produce Estriol ($E_3$) alone; it requires precursors (DHEAS) from the **fetal adrenal glands**, making $E_3$ a marker of feto-placental well-being.

Q: Before the onset of puberty, the GnRH neurons are under the inhibitory control of?

Gamma amino butyric acid (GABA). ### Explanation The onset of puberty is governed by the "gonadostat" mechanism, which involves the removal of central inhibition on **Gonadotropin-Releasing Hormone (GnRH) neurons**. **1. Why GABA is the Correct Answer:** During the prepubertal period, the hypothalamic-pituitary-gonadal (HPG) axis is kept dormant primarily through **tonic neural inhibition**. **Gamma-amino butyric acid (GABA)**, the major inhibitory neurotransmitter in the brain, acts on GnRH neurons to suppress their pulsatile release. As puberty approaches, there is a "brake release" phenomenon where GABAergic tone decreases and excitatory inputs (like Kisspeptin and Glutamate) increase, leading to the high-frequency GnRH pulses required for puberty. **2. Analysis of Incorrect Options:** * **Option A (Glycine):** While Glycine is an inhibitory neurotransmitter, it acts primarily in the spinal cord and brainstem, not in the hypothalamic regulation of GnRH. * **Option B (Glutamate):** Glutamate is an **excitatory** neurotransmitter. It stimulates GnRH release and its activity increases *at* the onset of puberty, rather than inhibiting it beforehand. * **Option D (Beta-endorphin):** Endogenous opioids like beta-endorphins do inhibit GnRH (often seen in exercise-induced amenorrhea or stress), but they are not the primary mediators responsible for the prepubertal quiescent state. **3. High-Yield Clinical Pearls for NEET-PG:** * **Kisspeptin:** This is the "master switch" of puberty. It is a potent stimulator of GnRH neurons. Puberty begins when Kisspeptin levels rise, overcoming GABAergic inhibition. * **Precocious Puberty:** Lesions in the hypothalamus (like hamartomas) can disrupt this inhibitory control, leading to early activation of the HPG axis. * **Nocturnal Pulses:** The first sign of impending puberty is the appearance of LH pulses during **sleep**.

Question 1

Spermatogenesis is regulated by a negative feedback control system in which FSH stimulates the steps in sperm cell formation. Which negative feedback signal associated with sperm cell production inhibits pituitary formation of FSH?

Accepted Answer

Inhibin

Answer

Testosterone

Answer

Estrogen

Answer

LH

Question 2

All of the following statements regarding Sertoli cells are TRUE, EXCEPT:

Accepted Answer

Stimulated by FSH

Answer

Secretes inhibin

Answer

Secretes androgen binding protein

Answer

Forms blood-testis barrier

Question 3

Sertoli cells play a key role in which of the following processes?

Accepted Answer

Spermiogenesis

Answer

Testosterone secretion

Answer

Secretion of seminal fluid

Answer

Production of germ cells

Question 4

Which of the following hormones is responsible for inhibiting lactation during pregnancy?

Accepted Answer

Progesterone

Answer

Human placental lactogen

Answer

Oxytocin

Answer

Prolactin

Question 5

Maximum function of the corpus luteum occurs when?

Accepted Answer

8-9 days after ovulation

Answer

At ovulation

Answer

Before ovulation

Answer

3 days after ovulation

Question 6

Which of the following statements regarding Anti-Müllerian hormone is false?

Accepted Answer

AMH is secreted by Leydig cells.

Answer

It causes regression of the ipsilateral Müllerian duct.

Answer

It controls rapid gubernacular growth necessary for the transabdominal descent of the testis.

Answer

AMH levels in women reflect ovarian follicle reserve.

Question 7

Which of the following is NOT secreted by the placenta?

Accepted Answer

Prolactin

Answer

Human Placental Lactogen (HPL)

Answer

Human Chorionic Gonadotropin (HCG)

Answer

Progesterone

Question 8

All the following are true about human chorionic gonadotropin (HCG) except:

Accepted Answer

It is secreted by the syncytiotrophoblast.

Answer

It has luteotrophic action.

Answer

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

Answer

It is a glycoprotein.

Question 9

Before the onset of puberty, the GnRH neurons are under the inhibitory control of?

Accepted Answer

Gamma amino butyric acid (GABA)

Answer

Glycine

Answer

Glutamate

Answer

Beta-endorphin

Question 10

Recruitment of follicles to form primordial follicles is done by which hormone?

Accepted Answer

Follicle stimulating hormone

Answer

Estrogen

Answer

HCG

Answer

LH

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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