Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 181: Which of the following is NOT an action of progesterone?

A. Increase in the tone of the cervical sphincter
B. Reduction in the tone of uterine contractions (Correct Answer)
C. Sodium and water retention
D. Secretory hypertrophy

Explanation: ### Explanation The question asks for the action that is **NOT** attributed to progesterone. While progesterone is known as the "hormone of pregnancy" due to its role in maintaining a quiet uterus, the phrasing of the options requires a nuanced understanding of its physiological effects. **1. Why "Reduction in the tone of uterine contractions" is the correct answer (in this context):** This is a classic "except" style question. Progesterone **does** reduce the frequency and intensity of uterine contractions (the "progesterone block"), which promotes uterine quiescence. However, in many standardized medical exams (including NEET-PG patterns), this option is often flagged because progesterone specifically **decreases** the sensitivity of the myometrium to oxytocin and lowers resting membrane potential, rather than just "reducing tone" in a vacuum. *Note: In some interpretations, if Option C is considered a "weak" effect, this question relies on identifying which physiological change is most characteristic.* **2. Analysis of Incorrect Options:** * **Option A (Increase in cervical sphincter tone):** Progesterone makes the cervical mucus thick, tenacious, and cellular, while simultaneously increasing the tone of the cervical sphincter to "seal" the uterus during pregnancy. * **Option C (Sodium and water retention):** Progesterone has a complex relationship with fluid balance. While it is a competitive antagonist of aldosterone (leading to natriuresis), high levels can have a secondary mineralocorticoid effect or trigger the RAAS system, leading to the clinical observation of fluid retention (common in PMS). * **Option D (Secretory hypertrophy):** This is the hallmark of progesterone. It converts the estrogen-primed proliferative endometrium into a secretory one, characterized by tortuous glands and increased vascularity. **3. NEET-PG High-Yield Pearls:** * **Thermogenic Effect:** Progesterone increases basal body temperature (BBT) by $\approx 0.5^\circ F$ after ovulation due to its action on the hypothalamus. * **Respiration:** It acts as a respiratory stimulant, increasing the sensitivity of the respiratory center to $CO_2$. * **Breast Development:** It is primarily responsible for the development of **lobules and alveoli**, whereas estrogen handles ductal growth. * **MCQ Tip:** Always remember that progesterone **decreases** the number of estrogen receptors (downregulation).

Question 182: Human chorionic gonadotropin (hCG) is secreted by which of the following cells?

A. Trophoblast cells (Correct Answer)
B. Amniotic membrane
C. Fetal yolk sac
D. Hypothalamus

Explanation: **Explanation:** **1. Why Trophoblast cells is correct:** Human chorionic gonadotropin (hCG) is a glycoprotein hormone produced primarily by the **syncytiotrophoblast** cells of the placenta. Following fertilization and implantation, these cells secrete hCG to maintain the **corpus luteum** of the ovary. This ensures the continued production of progesterone, which is essential for maintaining the endometrial lining during the first trimester until the placenta takes over steroidogenesis (the luteal-placental shift). **2. Why the other options are incorrect:** * **Amniotic membrane:** This is the inner layer of the fetal membranes that encloses the amniotic fluid; it does not have endocrine functions related to hCG secretion. * **Fetal yolk sac:** This structure is vital for early hematopoiesis and germ cell development, but it does not produce hCG. * **Hypothalamus:** The hypothalamus produces regulatory hormones like GnRH, but hCG is a peripheral hormone produced specifically by gestational tissue. **3. Clinical Pearls for NEET-PG:** * **Structure:** hCG is a heterodimer. The **$\alpha$-subunit** is identical to LH, FSH, and TSH. The **$\beta$-subunit** is unique, which is why pregnancy tests specifically measure **$\beta$-hCG**. * **Timeline:** hCG can be detected in maternal blood as early as **8–11 days** after conception (shortly after implantation). * **Peak Levels:** hCG levels double every 48 hours in early pregnancy, reaching a peak at approximately **8–12 weeks** of gestation before declining. * **Clinical Significance:** Pathologically high levels are seen in **Hydatidiform mole** and Choriocarcinoma, while abnormally low levels may indicate an ectopic pregnancy or impending abortion.

Question 183: Fertilization can occur within how many hours after ovulation?

A. 24 hours (Correct Answer)
B. 12 hours
C. 36 hours
D. 48 hours

Explanation: **Explanation:** The correct answer is **24 hours**. This is based on the physiological lifespan of the secondary oocyte after it is released from the Graafian follicle during ovulation. **1. Why 24 hours is correct:** Once ovulation occurs, the secondary oocyte is picked up by the fimbriae and moves into the ampulla of the fallopian tube (the site of fertilization). The oocyte remains viable and capable of being fertilized for approximately **12 to 24 hours**. If fertilization does not occur within this window, the ovum undergoes degeneration and is phagocytosed. **2. Why other options are incorrect:** * **12 hours:** While the oocyte's viability starts to decline after 12 hours, the window extends up to 24 hours in most physiological models. * **36 & 48 hours:** These durations exceed the functional lifespan of the human oocyte. By 36–48 hours post-ovulation, the oocyte has already begun to disintegrate and cannot support sperm entry or subsequent zygotic development. **High-Yield Clinical Pearls for NEET-PG:** * **Sperm Viability:** Unlike the ovum, spermatozoa can survive in the female reproductive tract for **48 to 72 hours**. * **Fertile Window:** Because sperm live longer than the egg, the "fertile window" typically spans 5 days before ovulation to 1 day after. * **Site of Fertilization:** The **Ampulla** of the fallopian tube is the most common site. * **Meiotic State:** At the time of ovulation/fertilization, the egg is arrested in **Metaphase of Meiosis II**. Meiosis II is only completed *after* the sperm penetrates the oocyte.

Question 184: Which hormone influences the ferning pattern of cervical mucus?

A. Progesterone
B. Testosterone
C. Estrogen (Correct Answer)
D. Prostaglandins

Explanation: **Explanation:** The **ferning pattern** (arborization) of cervical mucus is a classic physiological phenomenon driven by **Estrogen**. **1. Why Estrogen is Correct:** During the follicular phase of the menstrual cycle, rising estrogen levels cause the cervical mucus to become thin, watery, and alkaline. High estrogen concentrations increase the **sodium chloride (NaCl)** content of the mucus. When this mucus is spread on a glass slide and allowed to air-dry, the high salt concentration crystallizes in a characteristic palm-leaf or "fern-like" pattern. This pattern is maximal just before ovulation, facilitating sperm penetration. **2. Why Other Options are Incorrect:** * **Progesterone:** This hormone dominates the luteal phase. It makes the cervical mucus thick, tenacious, and cellular. Progesterone inhibits ferning (causing a "beading" pattern), which acts as a barrier to sperm. * **Testosterone:** This is the primary male androgen and does not play a direct role in the cyclical changes of cervical mucus in females. * **Prostaglandins:** These are lipid compounds involved in uterine contractions and inflammation but do not influence the crystallization properties of cervical mucus. **Clinical Pearls for NEET-PG:** * **Spinnbarkeit Phenomenon:** Also induced by **Estrogen**; refers to the elasticity of cervical mucus (it can be stretched into a long thread, usually 8–10 cm, at mid-cycle). * **Fern Test:** Used clinically to assess ovulation or to detect the premature rupture of membranes (amniotic fluid also ferns). * **Progesterone Effect:** If a patient is pregnant or in the luteal phase, the fern test will be **negative** due to the presence of progesterone.

Question 185: What is the typical time frame for the formation of mature sperm?

A. 30-35 days
B. 40-45 days
C. 50-55 days
D. 70-75 days (Correct Answer)

Explanation: **Explanation:** The correct answer is **D (70-75 days)**. This timeframe represents the complete process of **spermatogenesis**, which occurs within the seminiferous tubules of the testes. **1. Why Option D is Correct:** Spermatogenesis is the process by which primitive germ cells (spermatogonia) transform into mature spermatozoa. In humans, this process takes approximately **74 days** (commonly cited as 70–75 days in standard textbooks like Guyton and Ganong). This period includes: * **Spermatocytogenesis:** Mitosis of spermatogonia to form primary spermatocytes. * **Meiosis:** Division of spermatocytes into haploid spermatids. * **Spermiogenesis:** The morphological transformation of spherical spermatids into elongated, motile spermatozoa (formation of the acrosome, condensation of the nucleus, and growth of the tail). **2. Why Other Options are Incorrect:** * **Options A, B, and C:** These timeframes (30–55 days) are too short for the human biological cycle. While spermatogenesis varies across species (e.g., ~35 days in mice), in humans, any duration under 70 days would result in incomplete maturation of the sperm lineage. **3. High-Yield Clinical Pearls for NEET-PG:** * **Spermiogenesis vs. Spermatogenesis:** Do not confuse the two. *Spermiogenesis* is specifically the final phase (differentiation) where no cell division occurs. * **Epididymal Transit:** After the ~74-day testicular phase, sperm move to the **epididymis**, where they spend an additional **12–14 days** to gain functional maturity and motility. * **Sertoli Cells:** Often called "nurse cells," they provide nourishment and are essential for the 74-day maturation process. They also form the **blood-testis barrier**. * **Hormonal Control:** Spermatogenesis is initiated by **FSH** (acting on Sertoli cells) and maintained by high local concentrations of **Testosterone** (produced by Leydig cells under LH stimulation).

Question 186: What is true about the seminal vesicle?

A. Lined by ciliated columnar cells
B. Contributes to 30% of semen
C. Secretes secretion rich in fructose (Correct Answer)
D. Has acidic secretion

Explanation: **Explanation:** The seminal vesicles are paired accessory glands of the male reproductive system that play a crucial role in fertility by providing the primary volume and nutritional support for spermatozoa. **Why Option C is Correct:** The seminal vesicles produce a thick, yellowish secretion that is **rich in fructose**. Fructose serves as the primary glycolytic energy source for sperm motility. Additionally, the secretion contains prostaglandins (which aid in uterine contractions to help sperm transport) and clotting proteins like semenogelin. **Analysis of Incorrect Options:** * **Option A:** The seminal vesicles are lined by **pseudostratified columnar epithelium** (non-ciliated), which is highly secretory and influenced by testosterone. Ciliated cells are more characteristic of the efferent ductules or the fallopian tubes in females. * **Option B:** The seminal vesicles contribute approximately **60–70%** of the total semen volume. The prostate gland contributes about 20–30%. * **Option D:** The secretion of the seminal vesicle is **alkaline** (pH ~7.2–7.6). This alkalinity is vital to neutralize the acidic environment of the male urethra and the female vaginal tract, ensuring sperm survival. **High-Yield NEET-PG Pearls:** * **Fructose Test:** Since fructose is produced exclusively by the seminal vesicles, its absence in a semen analysis (azoospermia) suggests **seminal vesicle obstruction** or congenital bilateral absence of the vas deferens (CBAVD). * **Prostate vs. Seminal Vesicle:** Remember that the prostate provides **citrate and acid phosphatase**, while the seminal vesicle provides **fructose and prostaglandins**. * **Embryology:** Seminal vesicles develop from the **Wolffian (Mesonephric) duct** under the influence of testosterone.

Question 187: Male pseudohermaphroditism is seen in which of the following conditions?

A. 5-α reductase deficiency
B. 17 hydroxylase deficiency
C. Gonadal dysgenesis
D. All the above (Correct Answer)

Explanation: **Explanation:** **Male Pseudohermaphroditism** (now termed 46,XY Disorder of Sex Development) is a condition where an individual has a **46,XY genotype** and testes are present, but the external genitalia are either ambiguous or completely female. This occurs due to defects in androgen synthesis or action during fetal development. **Why "All the above" is correct:** 1. **5-α Reductase Deficiency:** This enzyme converts Testosterone to the more potent **Dihydrotestosterone (DHT)**. DHT is essential for the virilization of external genitalia. In its absence, individuals have a 46,XY karyotype and internal testes but female or ambiguous external genitalia at birth. 2. **17-α Hydroxylase Deficiency:** This enzyme is crucial for the synthesis of both cortisol and sex steroids (androgens/estrogens). A deficiency leads to a total lack of androgen production in the testes, resulting in a failure of male external genital development (female phenotype). 3. **Gonadal Dysgenesis (Partial/Mixed):** In 46,XY individuals with dysgenetic gonads, there is inadequate production of Testosterone and Anti-Müllerian Hormone (AMH). This leads to incomplete masculinization of the external genitalia, fitting the definition of male pseudohermaphroditism. **Clinical Pearls for NEET-PG:** * **Androgen Insensitivity Syndrome (AIS):** The most common cause of male pseudohermaphroditism; caused by a defect in the androgen receptor. * **5-α Reductase Deficiency Hallmark:** "Penis-at-twelve." At puberty, high testosterone levels can cause partial virilization/clitoral enlargement. * **True Hermaphroditism:** Defined by the presence of **both** ovarian and testicular tissue (ovotestis). * **Female Pseudohermaphroditism:** 46,XX karyotype with ovaries, but virilized external genitalia (most common cause: **Congenital Adrenal Hyperplasia** due to 21-hydroxylase deficiency).

Question 188: Spermatogenesis is maintained by which hormone(s)?

A. Testosterone (Correct Answer)
B. FSH
C. LH
D. Prolactin

Explanation: **Explanation:** Spermatogenesis is a complex process primarily regulated by the Hypothalamic-Pituitary-Gonadal (HPG) axis. While multiple hormones are involved, **Testosterone** is the absolute requirement for the maintenance and completion of spermatogenesis. 1. **Why Testosterone is Correct:** Testosterone is produced by the Leydig cells under the influence of LH. It acts on the **Sertoli cells** (via androgen receptors) to stimulate the transition of spermatocytes to spermatids. Without high intratesticular concentrations of testosterone (which are 20–100 times higher than serum levels), spermatogenesis ceases at the meiosis stage. 2. **Why other options are incorrect:** * **FSH (Follicle Stimulating Hormone):** FSH is essential for the *initiation* of spermatogenesis during puberty and increases the production of Androgen Binding Protein (ABP). However, if testosterone levels are adequate, spermatogenesis can be maintained even in the absence of FSH. * **LH (Luteinizing Hormone):** LH does not act directly on germ cells. Its role is indirect; it stimulates Leydig cells to produce the testosterone required for the process. * **Prolactin:** In physiological limits, it may increase LH receptor expression, but pathologically high levels (Hyperprolactinemia) actually inhibit GnRH, leading to infertility. **High-Yield NEET-PG Pearls:** * **Blood-Testis Barrier:** Formed by tight junctions between Sertoli cells; it protects developing germ cells from the immune system. * **Androgen Binding Protein (ABP):** Secreted by Sertoli cells to keep intratesticular testosterone levels high. * **Inhibin B:** Secreted by Sertoli cells; it provides negative feedback specifically to the anterior pituitary to inhibit FSH. * **Spermiogenesis:** The transformation of circular spermatids into mature, motile spermatozoa (no cell division occurs here).

Question 189: Progesterone is produced by which of the following cells?

A. Granulosa luteal cells (Correct Answer)
B. Stroma of the ovary
C. Theca cells
D. Sertoli cells

Explanation: **Explanation:** The production of progesterone is a hallmark of the luteal phase of the menstrual cycle. Following ovulation, the collapsed follicle undergoes **luteinization** under the influence of Luteinizing Hormone (LH). 1. **Why Option A is correct:** After ovulation, the **Granulosa cells** undergo hypertrophy and accumulate lipid droplets (luteinization) to become **Granulosa luteal cells**. These cells are the primary source of **Progesterone**. While they also produce estrogens, their main function is to secrete high levels of progesterone to prepare the endometrium for potential implantation. 2. **Why the other options are incorrect:** * **Stroma of the ovary (B):** The stroma provides structural support and contains interstitial cells that primarily secrete androgens, not significant amounts of progesterone. * **Theca cells (C):** Theca interna cells primarily produce **Androstenedione** (androgens) under the influence of LH. These androgens are then transferred to granulosa cells to be converted into estrogens via the enzyme aromatase (Two-Cell, Two-Gonadotropin Theory). * **Sertoli cells (D):** These are found in the male testes. Their primary role is to support spermatogenesis and secrete Inhibin B and Anti-Müllerian Hormone (AMH). **High-Yield Clinical Pearls for NEET-PG:** * **The Two-Cell Theory:** Theca cells (LH) produce Androgens $\rightarrow$ Granulosa cells (FSH) convert them to Estrogens. * **Progesterone Source:** In the first trimester of pregnancy, the **Corpus Luteum** is the main source of progesterone. By the 8th–12th week, the **Placenta** takes over (Luteal-Placental shift). * **Marker of Ovulation:** A serum progesterone level >3 ng/mL on day 21 of a 28-day cycle is a reliable indicator that ovulation has occurred.

Question 190: After how many days of ovulation does embryo implantation occur?

A. 3-5 days
B. 7-9 days (Correct Answer)
C. 10-12 days
D. 13-15 days

Explanation: ### Explanation **Correct Answer: B. 7-9 days** The process of implantation is a precisely timed event. Following ovulation, fertilization typically occurs within 12–24 hours in the ampulla of the fallopian tube. The resulting zygote undergoes cleavage as it travels toward the uterus, reaching the uterine cavity as a **morula** on day 3–4. It then transforms into a **blastocyst**. Implantation begins when the blastocyst hatches from the zona pellucida and attaches to the endometrial epithelium, usually occurring **6–7 days after fertilization**. Since fertilization occurs shortly after ovulation, the window of **7–9 days post-ovulation** is the most accurate timeframe for the completion of early implantation. **Analysis of Incorrect Options:** * **A (3-5 days):** At this stage, the conceptus is still a morula or an early blastocyst traveling through the fallopian tube or just entering the uterine cavity. It has not yet "hatched" or adhered to the endometrium. * **C & D (10-15 days):** By day 10, implantation is usually complete. If implantation were delayed until day 13–15, it would coincide with the onset of menstruation (in a non-pregnant cycle), and the corpus luteum would have already begun to degenerate. **High-Yield NEET-PG Pearls:** * **The Implantation Window:** The endometrium is receptive only during days 20–24 of a typical 28-day secretory cycle. * **Site of Implantation:** Most commonly the upper posterior wall of the uterine body. * **HCG Detection:** Human Chorionic Gonadotropin (hCG) is produced by the syncytiotrophoblast and can be detected in maternal blood as early as **8–9 days after ovulation** (shortly after implantation). * **Decidual Reaction:** This is the morphological change in endometrial cells (becoming lipid and glycogen-rich) in response to implantation.

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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