Reproductive Physiology Practice Questions

Q: When does fertilization normally occur after ovulation?

Within 12-24 hours. **Explanation:** The correct answer is **A. Within 12-24 hours.** **1. Why Option A is Correct:** Fertilization is highly time-sensitive due to the limited lifespan of the secondary oocyte. After ovulation, the ovum is picked up by the fimbriae and moves into the **ampulla of the fallopian tube** (the most common site of fertilization). The human ovum remains viable and capable of being fertilized for only **12 to 24 hours**. If fertilization does not occur within this window, the ovum begins to degenerate and is eventually phagocytized. **2. Why Other Options are Incorrect:** * **Options B, C, and D:** These timeframes exceed the biological viability of the unfertilized oocyte. While **spermatozoa** can survive in the female reproductive tract for approximately **48 to 72 hours** (waiting for the egg), the egg itself cannot wait that long. Therefore, for successful conception, coitus must occur close to the time of ovulation. **3. NEET-PG High-Yield Clinical Pearls:** * **Site of Fertilization:** The **Ampulla** of the fallopian tube is the specific site where fertilization occurs. * **Sperm Capacitation:** Before a sperm can fertilize an egg, it must undergo "capacitation" in the female reproductive tract, a process taking about **7 hours** to remove protective coatings from the acrosome. * **Zygote Transport:** Once fertilized, the zygote stays in the fallopian tube for about **3–4 days** before entering the uterine cavity. * **Implantation:** This typically occurs **6–7 days** after fertilization (around day 21 of a 28-day cycle), usually at the blastocyst stage. * **The "Window of Fertility":** Considering sperm longevity (3 days) and ovum viability (1 day), the fertile period is generally considered to be 3 days before to 1 day after ovulation.

Q: Cornification Index is maximum in which phase of the menstrual cycle?

Late proliferative phase. **Explanation:** The **Cornification Index (CI)** refers to the percentage of cornified (superficial) cells found in a vaginal smear. This index is a direct reflection of **estrogen** activity on the vaginal epithelium. Estrogen promotes the maturation of the vaginal mucosa, leading to the accumulation of superficial squamous cells characterized by pyknotic nuclei and acidophilic cytoplasm. 1. **Why Late Proliferative Phase is correct:** During the menstrual cycle, estrogen levels rise steadily throughout the proliferative phase, reaching their **peak just before ovulation** (the late proliferative phase). Consequently, the stimulation of the vaginal epithelium is maximal at this point, resulting in the highest Cornification Index (often >50-60%). 2. **Why other options are incorrect:** * **Early Proliferative Phase:** Estrogen levels are just beginning to rise; the smear is dominated by basal and parabasal cells, leading to a low CI. * **Early and Late Secretory Phases:** After ovulation, **progesterone** becomes the dominant hormone. Progesterone antagonizes the effects of estrogen on the vaginal mucosa, causing "shriveling" or folding of cells and an increase in intermediate cells (precornified cells). This leads to a significant decrease in the Cornification Index. **High-Yield Facts for NEET-PG:** * **Karyopyknotic Index (KI):** Also reaches its maximum during the **ovulatory/late proliferative phase** (measures cells with small, dense nuclei). * **Progesterone Effect:** Leads to the formation of **"Navicular cells"** (boat-shaped cells) and increased cellular clumping. * **Fern Test:** Also maximal in the late proliferative phase due to high estrogen and NaCl content in cervical mucus. * **Spinnbarkeit Phenomenon:** Maximum elasticity of cervical mucus occurs just before ovulation (Late Proliferative Phase).

Q: Which of the following hormones are involved in the initiation of lactation?

Oxytocin, Prolactin, and Human Placental Lactogen (HPL). ### Explanation The initiation and maintenance of lactation (Lactogenesis) is a complex neuroendocrine process requiring the synergistic action of several hormones. **1. Why Option A is Correct:** * **Prolactin:** The primary hormone for milk production. During pregnancy, it promotes the development of mammary alveoli. Postpartum, the drop in estrogen and progesterone allows prolactin to initiate milk secretion. * **Oxytocin:** Responsible for the **"Milk Ejection Reflex"** (Let-down reflex). It causes contraction of the myoepithelial cells surrounding the alveoli, squeezing milk into the ducts. * **Human Placental Lactogen (HPL):** Also known as Human Chorionic Somatomammotropin (hCS). It mimics prolactin and growth hormone, preparing the breast tissue during pregnancy for future lactation. **2. Why Other Options are Incorrect:** * **Thyroid Hormone (Options B & C):** While thyroid hormones are permissive for overall metabolic health and can influence milk volume, they are not primary mediators for the *initiation* of lactation. * **Progesterone (Option D):** Progesterone is actually an **inhibitor** of lactation during pregnancy. It prevents prolactin from acting on the breast tissue. Lactation only begins once progesterone levels plummet following the delivery of the placenta. **3. NEET-PG High-Yield Pearls:** * **Mammogenesis:** Development of breasts (Estrogen for ducts; Progesterone for alveoli). * **Lactogenesis:** Initiation of milk secretion (Prolactin). * **Galactokinesis:** Milk ejection (Oxytocin). * **Galactopoiesis:** Maintenance of lactation (Prolactin and Suckling stimulus). * **Suckling Stimulus:** Inhibits **Dopamine** (Prolactin Inhibiting Factor) in the hypothalamus, leading to increased Prolactin levels.

Q: What is the peak level of plasma progesterone in the luteal phase?

15 ng/ml. **Explanation:** The menstrual cycle is divided into the follicular and luteal phases. Progesterone levels are minimal (<1 ng/ml) during the follicular phase. Following ovulation, the **corpus luteum** forms and begins secreting large amounts of progesterone to prepare the endometrium for potential implantation (secretory phase). **Why 15 ng/ml is correct:** Progesterone levels begin to rise immediately after ovulation, reaching their peak approximately **7 to 9 days after the LH surge** (mid-luteal phase). In a typical 28-day cycle, this occurs around day 21-23. Standard medical textbooks (like Ganong and Guyton) cite the peak plasma concentration of progesterone during this period as approximately **15 ng/ml (range 10–25 ng/ml)**. **Analysis of Incorrect Options:** * **A. 5 ng/ml:** This level is often used as a threshold to confirm that ovulation has occurred, but it does not represent the maximum peak reached during a healthy luteal phase. * **B. 10 ng/ml:** While 10 ng/ml is a healthy mid-luteal level, it is generally considered the lower end of the "peak" range rather than the average maximum value. * **D. 30 ng/ml:** This value is significantly higher than the average peak in a non-pregnant cycle. Such high levels are typically only seen during the first trimester of pregnancy. **High-Yield Clinical Pearls for NEET-PG:** * **Source:** The corpus luteum is the primary source of progesterone in the luteal phase; the placenta takes over this role (luteal-placental shift) at approximately 7–9 weeks of gestation. * **Thermogenic Effect:** Progesterone acts on the hypothalamus to increase basal body temperature by **0.5°F to 1.0°F** after ovulation. * **Diagnostic Use:** A serum progesterone level >3 ng/ml on day 21 is a reliable indicator that ovulation has occurred.

Q: Which hormone produced by the human placenta has LH-like activity?

Human chorionic gonadotropin. **Explanation:** **Human Chorionic Gonadotropin (hCG)** is a glycoprotein hormone secreted by the syncytiotrophoblast of the placenta. It is structurally a heterodimer consisting of an alpha (α) and a beta (β) subunit. The α-subunit is identical to that of LH, FSH, and TSH; however, the **β-subunit of hCG is structurally very similar to the β-subunit of Luteinizing Hormone (LH)**. Due to this structural homology, hCG binds to the same **LH/hCG receptors**. Its primary physiological role is to "rescue" the corpus luteum from involution, maintaining progesterone production until the placenta takes over (the luteal-placental shift). **Analysis of Incorrect Options:** * **Progesterone:** A steroid hormone produced by the corpus luteum and later the placenta. It maintains the uterine lining but does not possess gonadotropic activity. * **Testosterone:** An androgenic steroid. While hCG stimulates Leydig cells in the male fetus to produce testosterone, testosterone itself does not have LH-like properties. * **Luteinizing Hormone (LH):** Produced by the anterior pituitary, not the placenta. While it has the same activity, the question specifically asks for a hormone *produced by the placenta*. **Clinical Pearls for NEET-PG:** * **Doubling Time:** In early normal pregnancy, hCG levels double approximately every 48 hours. * **Peak Levels:** hCG levels peak at around **8–10 weeks** of gestation and then decline to a lower plateau. * **Biological Mimicry:** Because of its LH-like activity, purified hCG is used clinically to **induce ovulation** in infertility treatments (acting as a surrogate LH surge). * **Thyroid Link:** At very high levels (e.g., Hydatidiform mole), hCG can bind to TSH receptors, potentially causing hyperthyroidism.

Q: Which of the following is the cause of amenorrhea in a lactating mother?

Increased prolactin level. **Explanation:** The correct answer is **D. Increased prolactin level.** **Mechanism of Lactational Amenorrhea:** During breastfeeding, the infant's suckling stimulus triggers the release of **Prolactin** from the anterior pituitary. While prolactin is essential for milk production, high levels exert a potent inhibitory effect on the reproductive axis. Specifically, prolactin inhibits the pulsatile secretion of **GnRH (Gonadotropin-Releasing Hormone)** from the hypothalamus. Reduced GnRH leads to a suppression of **LH (Luteinizing Hormone)** and **FSH (Follicle-Stimulating Hormone)** release from the pituitary. Without the LH surge, ovulation is inhibited, resulting in amenorrhea (Lactational Amenorrhea Method). **Analysis of Incorrect Options:** * **A & B (Increased LH/GnRH):** These are incorrect because prolactin actually **suppresses** the GnRH pulse generator and the subsequent release of LH. High levels of these hormones would trigger ovulation, not amenorrhea. * **C (Hyperestrogenic state):** Lactating mothers are actually in a **hypoestrogenic** state. Because FSH and LH are suppressed, the ovarian follicles do not develop, leading to very low estrogen levels. This hypoestrogenism is also why lactating women may experience vaginal dryness. **High-Yield NEET-PG Pearls:** * **Dopamine Connection:** Dopamine is the primary "Prolactin Inhibiting Factor." Drugs that block dopamine (e.g., Metoclopramide, Antipsychotics) cause hyperprolactinemia and secondary amenorrhea. * **Kisspeptin:** Recent studies show prolactin inhibits **Kisspeptin** neurons in the hypothalamus, which is the intermediary step in suppressing GnRH. * **Contraceptive Efficacy:** The Lactational Amenorrhea Method (LAM) is only reliable if the mother is exclusively breastfeeding, is less than 6 months postpartum, and remains amenorrheic.

Q: Meiosis in spermatogenesis occurs in which of the following steps?

Primary spermatocyte to secondary spermatocyte. ### Explanation The process of spermatogenesis involves the transformation of primitive germ cells into mature spermatozoa through a series of mitotic and meiotic divisions. **Why Option B is Correct:** The first meiotic division (**Meiosis I**) is the reductional division. It occurs when a **primary spermatocyte** (diploid, 46XY) undergoes division to form two **secondary spermatocytes** (haploid, 23X or 23Y). This is the critical step where the chromosome number is halved. **Analysis of Incorrect Options:** * **Option A:** There is no stage known as an "intermediate spermatocyte" in human spermatogenesis. The progression moves directly from Type B spermatogonia to primary spermatocytes. * **Option C:** The transition from secondary spermatocyte to round spermatid is **Meiosis II** (equational division). While this is technically a meiotic step, the question typically refers to the initiation of meiosis or the primary reductional phase. In many standardized exams, the conversion of primary to secondary is the hallmark of the meiotic phase. * **Option D:** The transformation of a round spermatid into an elongated spermatid (and eventually a mature spermatozoon) is called **Spermiogenesis**. This involves morphological changes (acrosome formation, tail development) but **no cell division**. **High-Yield Facts for NEET-PG:** * **Duration:** The entire process of spermatogenesis takes approximately **74 days**. * **Spermiation:** The process by which mature spermatozoa are released from Sertoli cells into the lumen of seminiferous tubules. * **Blood-Testis Barrier:** Formed by tight junctions between **Sertoli cells**; it protects developing germ cells (from primary spermatocytes onwards) from the immune system. * **Hormonal Control:** LH acts on Leydig cells (testosterone), while FSH acts on Sertoli cells to support spermatogenesis.

Q: How is iodide transported across the placenta?

Carrier-mediated process. **Explanation:** The transport of iodide across the placenta is a vital physiological process required for fetal thyroid hormone synthesis, which is essential for neurodevelopment. **1. Why "Carrier-mediated process" is correct:** Iodide does not cross the placenta by simple passive diffusion; instead, it is actively transported against a concentration gradient. This is primarily achieved through a **carrier-mediated process** involving the **Sodium-Iodide Symporter (NIS)**, located on the basal (maternal-facing) membrane of the syncytiotrophoblast. This ensures that the fetal plasma iodide concentration is generally higher than the maternal concentration, providing an adequate supply for the fetal thyroid gland, which begins functioning around the 12th week of gestation. **2. Why other options are incorrect:** * **Simple diffusion:** Iodide is a charged ion and cannot freely permeate the lipid bilayer of the placental membrane at rates sufficient to meet fetal demands. * **Endocytosis:** This mechanism is reserved for large molecules like Immunoglobulin G (IgG) or iron-bound transferrin, not for small ions like iodide. * **No transport:** This is incorrect as the fetus is entirely dependent on the maternal supply of iodide for its thyroid function; a lack of transport would lead to congenital hypothyroidism and cretinism. **Clinical Pearls for NEET-PG:** * **Wolff-Chaikoff Effect:** Excessive maternal intake of iodine can cross the placenta and temporarily inhibit fetal thyroid hormone synthesis, potentially causing a fetal goiter. * **Anti-thyroid drugs:** Drugs like Propylthiouracil (PTU) and Methimazole cross the placenta and can affect fetal thyroid status. PTU is generally preferred in the first trimester due to lower teratogenicity. * **Fetal Thyroid:** The fetal thyroid starts trapping iodine at **10–12 weeks** and becomes responsive to TSH by **20 weeks**.

Q: Production of spermatozoa is essential for reproduction. With respect to the spermatozoa tail structure, what is the unit that is essential for motility?

Axoneme. **Explanation:** The correct answer is **Axoneme**. **1. Why Axoneme is correct:** The axoneme is the structural and functional core of the spermatozoon tail (flagellum). It consists of a highly organized microtubule complex, typically in a **"9+2" arrangement** (nine peripheral doublets surrounding two central singlets). The motility is driven by **dynein arms** (ATPase enzymes) attached to these microtubules, which slide against each other to create the bending motion required for forward propulsion. Without the axoneme, the mechanical movement of the sperm is impossible. **2. Why other options are incorrect:** * **Tail:** While the tail is the overall anatomical structure used for swimming, the question asks for the specific *unit* or structural component essential for motility. The "tail" is too broad a term. * **Mitochondrial / Energy generating area:** These refer to the **middle piece** of the sperm. While mitochondria provide the ATP (energy) necessary for movement, they are the "fuel source," not the "motor unit" itself. Even with ATP, motility cannot occur without the functional machinery of the axoneme. **3. High-Yield Clinical Pearls for NEET-PG:** * **Kartagener’s Syndrome:** A subset of Primary Ciliary Dyskinesia caused by a deficiency in **dynein arms** within the axoneme. This leads to immotile sperm (infertility) and respiratory issues (due to impaired cilia). * **Sperm Maturation:** While the axoneme provides the machinery for movement, sperm only acquire *actual* motility in the **epididymis**. * **Capacitation:** This process occurs in the female reproductive tract, leading to "hyperactivated motility" required for fertilization.

Q: Which hormone is NOT important in the growth of the duct system of the breast?

Progesterone. ### Explanation The development of the breast (mammogenesis) is a complex process involving a synergy of multiple hormones. To answer this question, one must distinguish between the development of the **ductal system** versus the **tubulo-alveolar system**. **1. Why Progesterone is the Correct Answer:** While progesterone is essential for breast development, its primary role is the development of the **lobules and alveoli** (the milk-secreting structures). It acts on the terminal ends of the ducts to cause alveolar budding. It is **not** responsible for the linear growth or branching of the ductal system itself. **2. Analysis of Incorrect Options:** * **Estrogen (Primary Driver):** Although not an option here, it is the chief hormone for ductal growth. However, it cannot act alone. * **Growth Hormone (B) and Insulin (A):** These are "permissive" metabolic hormones. They are essential for providing the metabolic framework and growth environment required for estrogen to stimulate ductal elongation. * **Prolactin (C):** While primarily known for lactogenesis, prolactin (along with GH) is necessary for the initial development of the mammary ducts. In the absence of prolactin, estrogen-mediated ductal growth is significantly impaired. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Ductal Growth:** Estrogen + GH + Prolactin + Insulin + Glucocorticoids. * **Lobulo-alveolar Growth:** Progesterone + Estrogen + Prolactin + GH + Insulin + Glucocorticoids. * **Milk Production (Lactogenesis):** Prolactin (inhibited by high Estrogen/Progesterone during pregnancy). * **Milk Ejection (Galactokinesis):** Oxytocin (via contraction of myoepithelial cells). * **Puberty:** The first sign of puberty in girls is **Thelarche** (breast budding), driven primarily by Estrogen.

Question 1

When does fertilization normally occur after ovulation?

Accepted Answer

Within 12-24 hours

Answer

Within 24-48 hours

Answer

Within 48-72 hours

Answer

Within 72-96 hours

Question 2

Cornification Index is maximum in which phase of the menstrual cycle?

Accepted Answer

Late proliferative phase

Answer

Early secretory phase

Answer

Late secretory phase

Answer

Early proliferative phase

Question 3

Which of the following hormones are involved in the initiation of lactation?

Accepted Answer

Oxytocin, Prolactin, and Human Placental Lactogen (HPL)

Answer

Oxytocin, Prolactin, and Thyroid hormone

Answer

Oxytocin, Human Placental Lactogen (HPL), and Thyroid hormone

Answer

Oxytocin, Prolactin, and Progesterone

Question 4

What is the peak level of plasma progesterone in the luteal phase?

Accepted Answer

15 ng/ml

Answer

5 ng/ml

Answer

10 ng/ml

Answer

30 ng/ml

Question 5

Which hormone produced by the human placenta has LH-like activity?

Accepted Answer

Human chorionic gonadotropin

Answer

Progesterone

Answer

Testosterone

Answer

Luteinizing hormone

Question 6

Which of the following is the cause of amenorrhea in a lactating mother?

Accepted Answer

Increased prolactin level

Answer

Increased release of LH

Answer

Increased GnRH secretion

Answer

Hyperestrogenic state

Question 7

Meiosis in spermatogenesis occurs in which of the following steps?

Accepted Answer

Primary spermatocyte to secondary spermatocyte

Answer

Primary spermatocyte to intermediate spermatocyte

Answer

Secondary spermatocyte to round spermatid

Answer

Round spermatid to elongated spermatid

Question 8

How is iodide transported across the placenta?

Accepted Answer

Carrier-mediated process

Answer

Simple diffusion

Answer

Endocytosis

Answer

No transport

Question 9

Production of spermatozoa is essential for reproduction. With respect to the spermatozoa tail structure, what is the unit that is essential for motility?

Accepted Answer

Axoneme

Answer

Tail

Answer

Mitochondrial

Answer

Energy generating area

Question 10

Which hormone is NOT important in the growth of the duct system of the breast?

Accepted Answer

Progesterone

Answer

Insulin

Answer

Growth hormone

Answer

Prolactin

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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