Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 151: Which hormones stimulate spermatogenesis?

A. Thyroxine and parathormone
B. Insulin and glucagon
C. Antidiuretic hormone and Oxytocin
D. Testosterone and Follicle-stimulating hormone (Correct Answer)

Explanation: **Explanation:** Spermatogenesis is the complex process of sperm cell development occurring within the seminiferous tubules of the testes. This process is primarily regulated by the **Hypothalamic-Pituitary-Gonadal (HPG) axis**. **Why Option D is Correct:** * **Follicle-stimulating hormone (FSH):** Secreted by the anterior pituitary, FSH binds to receptors on **Sertoli cells**. It stimulates the production of Androgen Binding Protein (ABP) and initiates the process of spermatogenesis. * **Testosterone:** Luteinizing Hormone (LH) stimulates **Leydig cells** to produce testosterone. High local concentrations of testosterone (maintained by ABP) are essential for the maturation of spermatids into spermatozoa (spermiogenesis) and the maintenance of the germ cell population. **Why Other Options are Incorrect:** * **Option A:** Thyroxine (T4) regulates basal metabolic rate, and Parathormone (PTH) regulates calcium homeostasis. While thyroid disorders can indirectly affect fertility, they are not the primary drivers of spermatogenesis. * **Option B:** Insulin and Glucagon are pancreatic hormones responsible for glucose metabolism. * **Option C:** ADH (Vasopressin) regulates water retention in the kidneys, and Oxytocin is involved in milk ejection and uterine contractions. **High-Yield NEET-PG Pearls:** * **Sertoli Cells:** Often called "Nurse Cells"; they form the blood-testis barrier and provide nutrition to developing sperm. * **Inhibin B:** Secreted by Sertoli cells, it provides negative feedback specifically to FSH. * **LH vs. FSH:** Remember the mnemonic: **L**H acts on **L**eydig cells; **S**ertoli cells are stimulated by F**S**H. * **Duration:** The entire process of spermatogenesis takes approximately **74 days**.

Question 152: The secretory phase of the endometrium is primarily influenced by which hormone?

A. Estrogen
B. Progesterone (Correct Answer)
C. Prolactin
D. Pregnanediol

Explanation: ### Explanation The menstrual cycle is divided into two phases regarding the endometrium: the **Proliferative phase** and the **Secretory phase**. [1] **Why Progesterone is Correct:** The secretory phase occurs during the luteal phase of the ovarian cycle (days 15–28). After ovulation, the ruptured follicle transforms into the **corpus luteum**, which secretes high levels of **progesterone**. [1] Progesterone acts on the estrogen-primed endometrium to increase the tortuosity of endometrial glands, stimulate the secretion of glycogen-rich fluid, and increase the vascularity (spiral arteries). [1] These changes are essential for creating a receptive environment for the implantation of a fertilized ovum. **Analysis of Incorrect Options:** * **A. Estrogen:** This hormone dominates the **proliferative phase**. [1] It stimulates endometrial thickening and the growth of spiral arteries but does not induce the secretory changes. * **C. Prolactin:** Primarily responsible for milk production (lactogenesis) and the inhibition of GnRH; it does not have a direct stimulatory effect on the endometrial secretory phase. * **D. Pregnanediol:** This is the **urinary metabolite** of progesterone. [1] While its levels reflect progesterone production, it is an excretion product, not the active hormone influencing the endometrium. **High-Yield Clinical Pearls for NEET-PG:** * **The "Window of Implantation":** Occurs during the mid-secretory phase (days 20–24), driven by progesterone. * **Histological Hallmark:** The presence of **subnuclear vacuoles** in the endometrial glandular epithelium is the first sign of ovulation/progesterone effect (seen around day 16). * **Thermogenic Effect:** Progesterone causes a rise in basal body temperature (0.5–1.0°F) following ovulation. * **Withdrawal Bleeding:** Menstruation occurs due to the sudden decline in progesterone and estrogen levels following the involution of the corpus luteum.

Question 153: Ovulation can be diagnosed by all except:

A. Measuring day 14 serum progesterone (Correct Answer)
B. Rise in basal body temperature in the second half of cycle
C. Study of cervical mucus
D. Endometrial histology

Explanation: **Explanation:** The correct answer is **A (Measuring day 14 serum progesterone)** because it is timed incorrectly to diagnose ovulation. **1. Why Option A is correct (The "Except"):** In a standard 28-day menstrual cycle, ovulation occurs around Day 14. Progesterone is secreted by the **corpus luteum**, which only forms *after* ovulation has occurred. On Day 14, progesterone levels are still at basal follicular phase levels (<1 ng/mL). To confirm ovulation, serum progesterone must be measured during the **mid-luteal phase (Day 21)**, when levels typically peak (>3 ng/mL indicates ovulation). **2. Why the other options are incorrect (They ARE methods to diagnose ovulation):** * **Rise in Basal Body Temperature (BBT):** Progesterone is thermogenic. After ovulation, the rise in progesterone causes a 0.5°F to 1.0°F increase in BBT, resulting in a **biphasic** temperature chart. * **Study of Cervical Mucus:** Under progesterone influence (post-ovulation), cervical mucus becomes thick, cellular, and loses its elasticity (**decreased Spinnbarkeit**). It also loses the ability to "fern" on a glass slide, a change known as **anti-ferning**. * **Endometrial Histology:** A pre-menstrual endometrial biopsy showing **secretory changes** (e.g., subnuclear vacuolation) is the "gold standard" historical evidence that ovulation and subsequent progesterone production occurred. **NEET-PG High-Yield Pearls:** * **Best time for Progesterone test:** Day 21 of a 28-day cycle. * **Fern Test:** Estrogen causes ferning (positive before ovulation); Progesterone inhibits it (negative after ovulation). * **Mittelschmerz Sign:** Pelvic pain experienced by some women at the time of ovulation. * **LH Surge:** The most reliable predictor of *impending* ovulation (occurs 24–36 hours before the egg is released).

Question 154: The second polar body is released at which stage of oogenesis?

A. Birth
B. Puberty
C. Fertilization (Correct Answer)
D. None of the above

Explanation: **Explanation:** The process of oogenesis involves two distinct meiotic arrests, and understanding these is crucial for NEET-PG. **Why Fertilization is correct:** The secondary oocyte begins Meiosis II but is arrested in **Metaphase II**. This arrest is only broken upon the entry of a sperm (fertilization). When the sperm penetrates the zona pellucida and the oocyte membrane, it triggers the completion of Meiosis II, resulting in the formation of a mature ovum and the extrusion of the **second polar body**. Therefore, the release of the second polar body is synonymous with the completion of meiosis triggered by fertilization. **Why other options are incorrect:** * **Birth:** At birth, all primary oocytes are arrested in the **Prophase of Meiosis I** (specifically the Diplotene stage). No polar bodies are released at this stage. * **Puberty:** At puberty, under the influence of LH, the first meiotic division is completed just before ovulation. This results in the release of the **first polar body** and the formation of a secondary oocyte. **High-Yield Clinical Pearls for NEET-PG:** * **First Meiotic Arrest:** Occurs at the **Diplotene stage of Prophase I** (maintained by Oocyte Maturation Inhibitor - OMI). * **Second Meiotic Arrest:** Occurs at **Metaphase II** (maintained by Cytostatic Factor - CSF). * **First Polar Body:** Released just before ovulation. * **Second Polar Body:** Released at fertilization. * **Chromosomal Status:** The secondary oocyte is haploid (23 chromosomes) but has double the DNA content (2n) until the second polar body is released.

Question 155: What is the value of serum FSH in a normal adult female?

A. 1-5 IU/L
B. 5-20 IU/L (Correct Answer)
C. 20-40 IU/L
D. > 40 IU/L

Explanation: **Explanation:** The normal serum Follicle Stimulating Hormone (FSH) level in a reproductive-age female typically ranges between **5 and 20 IU/L**. FSH is secreted by the gonadotrophs of the anterior pituitary under the influence of GnRH. Its primary role is to stimulate the growth of ovarian follicles and the production of estrogen. * **Why Option B is correct:** During a normal menstrual cycle, FSH levels fluctuate but generally stay within the 5-20 IU/L range. It is lowest during the luteal phase and highest during the mid-cycle pre-ovulatory surge (where it can reach the upper limit of this range). * **Why Option A is incorrect:** Levels below 5 IU/L are typically seen in prepubertal girls or pathological states like hypogonadotropic hypogonadism (pituitary or hypothalamic failure). * **Why Option C is incorrect:** Levels between 20-40 IU/L are considered "perimenopausal." This elevation indicates a declining ovarian reserve, where the pituitary increases FSH production to compensate for reduced inhibin and estrogen feedback. * **Why Option D is incorrect:** FSH levels **> 40 IU/L** are diagnostic of **Menopause** or Premature Ovarian Failure (POF). At this stage, the exhaustion of follicles leads to a lack of negative feedback, causing a persistent, marked elevation in FSH. **High-Yield Clinical Pearls for NEET-PG:** 1. **Day 3 FSH:** Measuring FSH on the third day of the menstrual cycle is a classic test for **ovarian reserve**. Values >10-12 IU/L suggest a poor reserve. 2. **LH:FSH Ratio:** In **PCOS**, the LH:FSH ratio is typically reversed (often > 2:1 or 3:1). 3. **Gold Standard:** FSH is the most sensitive marker for diagnosing menopause compared to LH or Estrogen.

Question 156: During ejaculation, from which of the following structures are sperms released from their storage?

A. Epididymis (Correct Answer)
B. Vas deferens
C. Rete testes
D. Seminal vesicle

Explanation: **Explanation:** The correct answer is **Epididymis (Option A)**. **Why it is correct:** Spermatogenesis occurs in the seminiferous tubules, but the resulting spermatozoa are immotile. They are transported to the **epididymis**, specifically the **cauda (tail) of the epididymis**, which serves as the primary site for sperm maturation and long-term storage. During ejaculation, powerful sympathetic-mediated contractions of the smooth muscle in the epididymal walls propel the stored sperm into the vas deferens. **Why other options are incorrect:** * **Vas deferens (Option B):** While the vas deferens acts as a conduit for sperm transport during ejaculation, it is not the primary storage reservoir. Its main function is the rapid peristaltic transport of sperm toward the ejaculatory ducts. * **Rete testes (Option C):** This is a network of tubules located within the hilum of the testis that collects sperm from the seminiferous tubules and drains into the efferent ductules. It is a site of passage, not storage. * **Seminal vesicle (Option D):** A common misconception is that seminal vesicles store sperm. In reality, they secrete a thick, fructose-rich alkaline fluid that constitutes about 60-70% of the total semen volume. They do **not** contain or store spermatozoa. **High-Yield NEET-PG Pearls:** * **Sperm Maturation:** Sperm acquire motility and the ability to fertilize (decapacitation factors) during their 12–24 day transit through the epididymis. * **Blood-Testis Barrier:** Formed by **Sertoli cells** (tight junctions), protecting immunogenic sperm from the immune system. * **Emission vs. Ejaculation:** Emission (movement of semen into the urethra) is mediated by **Sympathetic** nerves (T11-L2), while Ejaculation is mediated by the **Pudendal nerve** (S2-S4) causing contraction of the bulbospongiosus muscle.

Question 157: Estrogen is secreted by which cells?

A. Granulosa cells (Correct Answer)
B. Theca luteal cells
C. Theca interna cells
D. Theca externa cells

Explanation: The synthesis of estrogen in the ovary is best explained by the **Two-Cell, Two-Gonadotropin Theory**. ### Why Granulosa Cells are Correct Estrogen (specifically Estradiol) is primarily synthesized in the **Granulosa cells**. While these cells lack the enzyme *17α-hydroxylase* to produce androgens from cholesterol, they are rich in the enzyme **Aromatase**. Under the influence of **FSH**, Granulosa cells take up androgens (androstenedione and testosterone) produced by the neighboring theca cells and convert them into estrogens via aromatization. ### Why Other Options are Incorrect * **Theca interna cells:** These cells possess LH receptors and the enzyme *17α-hydroxylase*. Under **LH** stimulation, they convert cholesterol into **androgens**. They cannot produce estrogen because they lack the aromatase enzyme. * **Theca luteal cells:** These are formed after ovulation (in the corpus luteum). While they contribute to the steroidogenic pool, the primary site of estrogen synthesis remains the granulosa (now granulosa-lutein) cells. * **Theca externa cells:** This is a connective tissue layer (fibroblast-like cells) that provides structural support and vascularity to the follicle but has no endocrine/steroidogenic function. ### High-Yield NEET-PG Pearls * **Rate-limiting step:** The conversion of cholesterol to pregnenolone (by P450scc) is the rate-limiting step in steroidogenesis. * **The "Two-Cell" Summary:** 1. **Theca Interna:** LH acts $\rightarrow$ cAMP $\rightarrow$ Cholesterol to Androstenedione. 2. **Granulosa:** FSH acts $\rightarrow$ cAMP $\rightarrow$ Aromatase converts Androstenedione to Estradiol. * **Dominant Follicle:** The follicle with the highest density of FSH receptors and highest aromatase activity becomes the dominant follicle.

Question 158: Efferent cremastric reflex is carried by which nerve?

A. Ilioinguinal nerve
B. Genito-femoral nerve (Correct Answer)
C. Iliohypogastric nerve
D. Pudendal nerve

Explanation: ### Explanation The **cremasteric reflex** is a superficial reflex elicited by lightly stroking the superior and medial aspect of the thigh. The normal response is the contraction of the cremaster muscle, which pulls the testis ipsilaterally toward the inguinal canal. **1. Why Option B is Correct:** The reflex arc involves two distinct branches of the **genitofemoral nerve (L1, L2)**: * **Afferent Limb:** Sensory fibers are carried by the **femoral branch** of the genitofemoral nerve (and the ilioinguinal nerve). * **Efferent Limb:** Motor fibers are carried by the **genital branch** of the genitofemoral nerve, which innervates the cremaster muscle. Since the question specifically asks for the **efferent** carrier, the genitofemoral nerve is the definitive answer. **2. Why Other Options are Incorrect:** * **A. Ilioinguinal nerve:** While it contributes to the **afferent** (sensory) limb of the reflex by supplying the skin of the upper medial thigh, it does not provide motor supply to the cremaster muscle. * **C. Iliohypogastric nerve:** This nerve supplies the skin above the pubis and the lateral gluteal region; it is not involved in the cremasteric reflex arc. * **D. Pudendal nerve:** This nerve (S2–S4) supplies the perineum and external anal/urethral sphincters. It is involved in the bulbocavernosus reflex, not the cremasteric reflex. **3. Clinical Pearls & High-Yield Facts:** * **Level of Integration:** The reflex is integrated at the **L1–L2** spinal cord levels. * **Clinical Significance:** The reflex is characteristically **absent in testicular torsion**, making it a vital diagnostic tool in the emergency department for "acute scrotum." * **Upper Motor Neuron (UMN) Lesions:** Like other superficial reflexes (e.g., abdominal reflex), the cremasteric reflex is lost in UMN lesions above the L1 level. * **Differential:** It remains present in epididymitis, helping distinguish it from torsion.

Question 159: A baby is born with a penis, a scrotum with no testes, no vagina, and XX chromosomes. What could cause this abnormality?

A. Abnormally high levels of human chorionic gonadotropin (HCG) production by the trophoblast cells
B. The presence of a testosterone-secreting tumor in the mother's right adrenal gland (Correct Answer)
C. Abnormally high levels of LH in the maternal blood
D. Abnormally low levels of testosterone in the maternal blood

Explanation: This clinical scenario describes **Female Pseudohermaphroditism** (46,XX DSD). The infant has female chromosomes (XX) and internal female structures (implied by the absence of testes), but the external genitalia have been virilized (penis and scrotum) due to exposure to excessive androgens during the critical period of sexual differentiation. ### **Explanation of the Correct Option** **Option B** is correct because the development of external male genitalia in an XX fetus requires the presence of androgens (specifically Testosterone and DHT) between the 8th and 12th weeks of gestation. If the mother has a **testosterone-secreting adrenal tumor**, these androgens cross the placenta and act on the fetal bipotential external genitalia. This causes the urogenital folds to fuse (forming a scrotum instead of labia majora) and the genital tubercle to enlarge into a penis. ### **Why Other Options are Incorrect** * **Option A & C:** HCG and LH are gonadotropins. While HCG stimulates the Leydig cells in a *male* fetus to produce testosterone, it cannot induce virilization in a female fetus unless there is an androgen source. High maternal LH/HCG does not directly cause masculinization of an XX fetus. * **Option D:** Low levels of maternal testosterone would result in normal female development. Masculinization requires *excess* androgens. ### **NEET-PG High-Yield Pearls** * **Most Common Cause:** The most common cause of female pseudohermaphroditism is **Congenital Adrenal Hyperplasia (CAH)**, specifically 21-hydroxylase deficiency, leading to excess fetal androgen production. * **Internal vs. External:** In these cases, internal organs (uterus/ovaries) are usually present because **Müllerian Inhibiting Substance (MIS)** is absent (since there are no testes). * **Prader Staging:** The degree of virilization of female external genitalia is graded using the Prader Scale. * **Key Concept:** External genitalia are "male" by default only if androgens are present; internal genitalia are "female" by default unless MIS is present.

Question 160: The laboratory report shows values of gonadotropin and ovarian hormones from a blood sample taken on day 20 of the menstrual cycle of a young woman. Whether her cycle was ovulatory or not may be validly assessed by the reported serum level of:

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

Explanation: **Explanation:** The correct answer is **Progesterone**. **1. Why Progesterone is the Correct Answer:** The menstrual cycle is divided into the follicular and luteal phases. Ovulation occurs around day 14, marking the transition. After ovulation, the ruptured follicle transforms into the **corpus luteum**, which primarily secretes **progesterone**. On **Day 20** (the mid-luteal phase), progesterone levels reach their peak. A serum progesterone level of **>3 ng/mL** (or ideally >10 ng/mL) is the gold standard biochemical evidence that ovulation has occurred. If the cycle were anovulatory, no corpus luteum would form, and progesterone levels would remain basal (<1 ng/mL). **2. Why Other Options are Incorrect:** * **FSH (Follicle Stimulating Hormone):** FSH peaks just before ovulation and remains low during the luteal phase due to negative feedback from estrogen and progesterone. It does not confirm ovulation. * **LH (Luteal Hormone):** While an "LH surge" triggers ovulation, it occurs around day 12–13. By day 20, LH levels have returned to baseline and cannot confirm if the egg was actually released. * **Oestradiol:** Estrogen peaks twice—once before ovulation and once during the mid-luteal phase. Because it is elevated in both phases, it is not a specific indicator of ovulation. **Clinical Pearls for NEET-PG:** * **Best day to measure Progesterone:** Day 21 of a 28-day cycle (Mid-luteal phase). * **Most accurate sign of ovulation:** Ultrasound (disappearance of the dominant follicle). * **Basal Body Temperature (BBT):** Increases by 0.5–1.0°F after ovulation due to the thermogenic effect of progesterone. * **Endometrial Biopsy:** If done on day 21, "secretory changes" confirm the action of progesterone and thus ovulation.

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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