Reproductive Physiology Practice Questions

Q: Oxytocin causes all of the following except:

Lactogenesis. **Explanation:** The correct answer is **A. Lactogenesis**. **1. Why Lactogenesis is the correct (Except) option:** Lactogenesis refers to the initiation of milk secretion in the mammary glands. This process is primarily mediated by **Prolactin**, which is secreted by the anterior pituitary. Oxytocin has no role in the synthesis or initiation of milk production; its function is purely mechanical and related to smooth muscle contraction. **2. Analysis of Incorrect Options:** * **Milk ejection (B) & Myoepithelial cell contraction (D):** These are the primary functions of Oxytocin in the breast. Oxytocin is released from the posterior pituitary in response to suckling (the **Milk Ejection Reflex** or Ferguson Reflex). it causes contraction of the **myoepithelial cells** surrounding the alveoli, forcing milk into the ducts. * **Contraction of uterine muscle (C):** Oxytocin acts on the G-protein coupled receptors of the myometrium to increase intracellular calcium, leading to powerful uterine contractions. This is essential for both the progression of labor and the prevention of postpartum hemorrhage (PPH). **3. High-Yield Clinical Pearls for NEET-PG:** * **Site of Synthesis:** Oxytocin is synthesized in the **Paraventricular nucleus** (primarily) and Supraoptic nucleus of the hypothalamus, then stored in the posterior pituitary. * **The "Love Hormone":** Beyond physical labor, it plays a role in social bonding and maternal behavior. * **Pharmacology Link:** Synthetic oxytocin (Pitocin) is the drug of choice for **Induction of Labor** and management of **Postpartum Hemorrhage (PPH)**. * **Reflex Type:** The milk ejection reflex is a **neuroendocrine reflex**. Unlike most hormones, Oxytocin operates on a **positive feedback mechanism** during labor.

Q: Plasma levels of hCG during pregnancy double approximately every:

2 days. **Explanation:** Human Chorionic Gonadotropin (hCG) is a glycoprotein hormone secreted by the **syncytiotrophoblast** of the developing placenta. Its primary physiological role is to maintain the corpus luteum, ensuring the continued secretion of progesterone until the placenta takes over steroidogenesis (the luteal-placental shift). **Why Option B is Correct:** In a normal intrauterine pregnancy, serum hCG levels rise exponentially during the first trimester. The **doubling time** of hCG is approximately **48 hours (2 days)** during the early weeks of gestation. This rapid increase is a hallmark of a viable, healthy pregnancy. hCG levels typically peak between **8 to 12 weeks** of gestation before gradually declining to a lower, stable plateau for the remainder of the pregnancy. **Why Other Options are Incorrect:** * **Option A (Daily):** While hCG rises rapidly, a 24-hour doubling time is abnormally fast and not the physiological standard. * **Options C & D (4 or 6 days):** A doubling time longer than 2 days (e.g., >72 hours) in early pregnancy is often a clinical red flag. Slow-rising hCG levels are frequently associated with **ectopic pregnancy** or impending **spontaneous abortion**. **High-Yield Clinical Pearls for NEET-PG:** * **Detection:** hCG can be detected in maternal blood as early as **6–8 days after conception** (around the time of implantation) and in urine by day 14. * **Subunits:** hCG consists of an alpha and a beta subunit. The **beta (β) subunit** is unique to hCG, making it the basis for pregnancy tests (the alpha subunit is identical to LH, FSH, and TSH). * **Clinical Utility:** Serial hCG monitoring is the "gold standard" for evaluating early pregnancy complications. If the level fails to increase by at least 66% in 48 hours, the pregnancy's viability is guarded. * **Pathological Peaks:** Extremely high levels of hCG are seen in **Hydatidiform mole** (Gestational Trophoblastic Disease) and multiple pregnancies.

Q: The ovarian cycle is initiated by:

FSH. **Explanation:** The ovarian cycle is a series of monthly events associated with the maturation of an egg. The initiation of this cycle is governed by the **Hypothalamic-Pituitary-Ovarian (HPO) axis**. **Why FSH is correct:** At the end of the previous menstrual cycle, estrogen and progesterone levels fall, removing the negative feedback on the pituitary. This leads to a rise in **Follicle-Stimulating Hormone (FSH)**. FSH is the primary hormone responsible for the "recruitment" of a cohort of primordial follicles from the resting pool. It binds to receptors on granulosa cells, stimulating follicular growth and the synthesis of estrogen. Without the initial rise in FSH, the follicular phase cannot begin. **Why other options are incorrect:** * **Estrogen:** Estrogen levels are low at the start of the cycle. Estrogen rises later in the follicular phase (secreted by growing follicles) to help select the dominant follicle and eventually trigger the LH surge. * **LH (Luteinizing Hormone):** While LH is present, its primary roles occur later: stimulating theca cells to produce androgens and triggering **ovulation** (via the LH surge). It does not initiate the cycle. * **Progesterone:** This hormone is dominant during the **luteal phase** (secreted by the corpus luteum). Its withdrawal is what triggers menstruation, but it does not initiate the growth of new follicles. **NEET-PG High-Yield Pearls:** * **The "FSH Window":** The brief period at the start of the cycle where FSH levels rise above a specific threshold is critical for follicle recruitment. * **Two-Cell, Two-Gonadotropin Theory:** LH acts on **Theca cells** (producing androgens), while FSH acts on **Granulosa cells** (converting androgens to estrogen via aromatase). * **Inhibin B:** Produced by granulosa cells under the influence of FSH; it provides negative feedback to specifically lower FSH levels mid-follicular phase.

Q: Upon contact between the sperm head and the zona pellucida, penetration of the sperm into the egg is allowed because of which of the following processes?

The acrosome reaction. **Explanation:** The correct answer is **A. The acrosome reaction.** **1. Why the Acrosome Reaction is Correct:** When a capacitated sperm binds to the **ZP3 receptors** on the zona pellucida (ZP), it triggers the acrosome reaction. This involves the fusion of the outer acrosomal membrane with the sperm's plasma membrane, leading to the release of proteolytic enzymes (primarily **Acrosin** and Hyaluronidase). These enzymes locally digest the glycoprotein matrix of the zona pellucida, creating a tunnel that allows the sperm to penetrate and reach the oocyte's plasma membrane. **2. Why the Other Options are Incorrect:** * **B. The Zona Reaction:** This occurs *after* the first sperm penetrates the egg. It involves the release of cortical granules (Cortical Reaction) that harden the zona pellucida to prevent **polyspermy** (entry of multiple sperm). * **C. The Perivitelline Space:** This is the fluid-filled space between the zona pellucida and the oocyte cell membrane. It is a structural location, not a process that facilitates penetration. * **D. Pro-nuclei Formation:** This is a late stage of fertilization that occurs after the sperm has already entered the egg and the second meiotic division is completed. **3. NEET-PG High-Yield Pearls:** * **Capacitation:** A 7-hour process in the female reproductive tract (primarily the isthmus of the fallopian tube) required for the sperm to become fertile; it must precede the acrosome reaction. * **ZP3:** The specific glycoprotein receptor on the zona pellucida responsible for species-specific sperm binding. * **Calcium (Ca²⁺) Influx:** The essential ion required to trigger the acrosome reaction upon sperm-ZP binding.

Q: All of the following physiological changes may be observed in a normal pregnancy, EXCEPT:

Increase in blood viscosity. **Explanation:** In a normal pregnancy, the correct answer is **A (Increase in blood viscosity)** because pregnancy is actually characterized by a **decrease in blood viscosity**. This occurs due to a disproportionate increase in plasma volume (~40–50%) compared to the increase in red cell mass (~20–30%), leading to **hemodilution** (physiological anemia of pregnancy). Lower viscosity reduces peripheral resistance, facilitating better placental perfusion. **Analysis of other options:** * **B. Fall in serum iron concentration:** Despite an increase in red cell mass, the demand for iron by the fetus and the expanded maternal blood volume exceeds dietary intake, leading to a typical fall in serum iron levels. * **C. Increase in serum iron binding capacity:** As iron stores deplete, the liver increases the production of Transferrin. This results in an increased Total Iron Binding Capacity (TIBC), a classic marker of pregnancy. * **D. Increase in blood oxygen carrying capacity:** Although there is hemodilution, the absolute total red cell mass increases (stimulated by erythropoietin). Therefore, the *total* oxygen-carrying capacity of the blood increases to meet the metabolic demands of the fetus and mother. **High-Yield NEET-PG Pearls:** * **Cardiac Output:** Increases by 30–50%, peaking at 28–32 weeks. * **Coagulation:** Pregnancy is a **hypercoagulable state** (increase in Factors VII, VIII, IX, X, and Fibrinogen; decrease in Protein S). * **ESR:** Always elevated in pregnancy due to increased fibrinogen; it is not a reliable marker for infection. * **Blood Pressure:** Diastolic BP typically decreases in the second trimester due to systemic vasodilation.

Q: Decidualization of the endometrium is primarily caused by which hormone?

Progesterone. **Explanation:** **Decidualization** is the process by which endometrial stromal cells transform into large, polygonal, glycogen-rich cells (decidual cells) to provide a supportive environment for the implanting embryo. **Why Progesterone is correct:** Progesterone is the "hormone of pregnancy." Following ovulation, the corpus luteum secretes high levels of progesterone. This hormone acts on the estrogen-primed endometrium to initiate the secretory phase. Progesterone triggers the differentiation of stromal fibroblasts into decidual cells, increases vascularity (spiral artery development), and stimulates uterine gland secretion. If implantation occurs, progesterone levels remain high to maintain this decidua; without it, the decidua sheds (menstruation). **Why other options are incorrect:** * **Estrogen:** While estrogen is essential for the **proliferative phase** (thickening the endometrial lining), it does not cause decidualization. It "primes" the tissue so that progesterone can act effectively. * **Inhibin:** Produced by the granulosa cells (Inhibin B) and corpus luteum (Inhibin A), its primary role is the negative feedback inhibition of FSH secretion from the anterior pituitary. * **FSH:** This gonadotropin is responsible for the recruitment and maturation of ovarian follicles; it has no direct effect on the morphological transformation of the endometrium. **NEET-PG High-Yield Pearls:** * **Decidua Basalis:** The part of the decidua at the implantation site that forms the maternal component of the placenta. * **Arias-Stella Reaction:** A benign change in endometrial glands (hypersecretory phenotype) due to high progesterone, often seen in ectopic pregnancy; it can be mistaken for malignancy. * **Window of Implantation:** Occurs approximately 6–10 days after the LH surge (Days 20–24 of a typical cycle) when progesterone levels are peak.

Q: What is the typical lifespan of the corpus luteum after ovulation in a non-pregnant female?

10 days. **Explanation:** The corpus luteum (CL) is a temporary endocrine structure formed from the remnants of the ovarian follicle after ovulation. Its primary function is to secrete progesterone to prepare the endometrium for potential implantation. **Why Option B is Correct:** In a typical 28-day menstrual cycle, ovulation occurs on Day 14. The corpus luteum remains functional and actively secretes hormones for approximately **10 to 12 days** (the functional lifespan). If fertilization does not occur, the lack of Human Chorionic Gonadotropin (hCG) leads to **luteolysis** (degeneration of the CL) around Day 24-26 of the cycle, eventually forming the fibrous *corpus albicans*. This decline in progesterone triggers menstruation. **Analysis of Incorrect Options:** * **Option A (5 days):** This is too short. A functional lifespan this brief would indicate a "Luteal Phase Defect," often leading to infertility as the endometrium cannot be maintained long enough for implantation. * **Option C (14 days):** While the total **Luteal Phase** of the menstrual cycle is consistently 14 days, the *active secretory lifespan* of the corpus luteum itself is approximately 10–12 days before it begins to involute and hormone levels drop. * **Option D (30 days):** This exceeds the length of a standard menstrual cycle. The CL only persists beyond 14 days if pregnancy occurs, where hCG "rescues" it to maintain the pregnancy for the first trimester. **NEET-PG High-Yield Pearls:** * **Hormonal Control:** The formation of the CL is triggered by the **LH Surge**. * **Life Extension:** In pregnancy, **hCG** (an LH analog) maintains the CL for about 8–12 weeks until the "Luteal-Placental Shift" occurs. * **Fixed Phase:** In the menstrual cycle, the **Luteal Phase is constant (14 days)**, whereas the Follicular Phase is variable. * **Inhibin B vs. A:** Inhibin B is dominant in the follicular phase; **Inhibin A** is the primary inhibin secreted by the corpus luteum.

Q: Ovulation occurs after the extrusion of which of the following?

First polar body. ### Explanation **Correct Answer: C. First polar body** **The Core Concept:** Oogenesis is a discontinuous process characterized by specific arrests. All primary oocytes are arrested in **Prophase of Meiosis I** (specifically the diplotene stage) since fetal life. Just before ovulation, the **LH surge** triggers the completion of Meiosis I. This division is unequal, resulting in a large **secondary oocyte** and a small, non-functional **first polar body**. Therefore, at the time of ovulation, the egg is technically a secondary oocyte that has already extruded the first polar body. **Analysis of Options:** * **A. Primary oocyte:** This is incorrect because the primary oocyte must complete Meiosis I to become a secondary oocyte before it can be released from the follicle. * **B. Female pronucleus:** This is incorrect as the pronucleus only forms *after* fertilization occurs and the second meiotic division is completed. * **D. Second polar body:** This is incorrect because the extrusion of the second polar body occurs only **after fertilization** (when the sperm penetrates the secondary oocyte), triggering the completion of Meiosis II. **High-Yield NEET-PG Pearls:** * **Arrest Points:** 1. **First Arrest:** Prophase I (Diplotene) — maintained by Oocyte Maturation Inhibitor (OMI). 2. **Second Arrest:** Metaphase II — occurs at ovulation and is only completed if fertilization happens. * **The "M" Rule:** Ovulation occurs at **M**etaphase II; the **M**eiosis II is completed only if **M**eets a sperm. * **Chromosomal Status:** The secondary oocyte (post-ovulation) is **haploid (23, X)** but contains double the DNA amount (2n) until the second polar body is shed.

Question 1

Oxytocin causes all of the following except:

Accepted Answer

Lactogenesis

Answer

Milk ejection

Answer

Contraction of uterine muscle

Answer

Myoepithelial cell contraction

Question 2

Which of the following statements regarding folliculogenesis and ovulation is INCORRECT?

Accepted Answer

Elevated and static levels of estradiol are essential for ovulation.

Answer

Follicular development and differentiation takes approximately 85 days.

Answer

AMH supports follicular development and oocyte maturation.

Answer

The first phase of follicular growth is gonadotropin-insensitive.

Question 3

Plasma levels of hCG during pregnancy double approximately every:

Accepted Answer

2 days

Answer

Daily

Answer

4 days

Answer

6 days

Question 4

The ovarian cycle is initiated by:

Accepted Answer

FSH

Answer

Estrogen

Answer

LH

Answer

Progesterone

Question 5

Upon contact between the sperm head and the zona pellucida, penetration of the sperm into the egg is allowed because of which of the following processes?

Accepted Answer

The acrosome reaction

Answer

The zona reaction

Answer

The perivitelline space

Answer

Pro-nuclei formation

Question 6

Which of the following statements regarding human chorionic gonadotropin (HCG) is false?

Accepted Answer

It is secreted by syncytiotrophoblasts.

Answer

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

Answer

It has a luteotrophic action.

Answer

It is a glycoprotein.

Question 7

All of the following physiological changes may be observed in a normal pregnancy, EXCEPT:

Accepted Answer

Increase in blood viscosity

Answer

Fall in serum iron concentration

Answer

Increase in serum iron binding capacity

Answer

Increase in blood oxygen carrying capacity

Question 8

Decidualization of the endometrium is primarily caused by which hormone?

Accepted Answer

Progesterone

Answer

Estrogen

Answer

Inhibin

Answer

Follicle Stimulating Hormone (FSH)

Question 9

What is the typical lifespan of the corpus luteum after ovulation in a non-pregnant female?

Accepted Answer

10 days

Answer

5 days

Answer

14 days

Answer

30 days

Question 10

Ovulation occurs after the extrusion of which of the following?

Accepted Answer

First polar body

Answer

Primary oocyte

Answer

Female pronucleus

Answer

Second polar body

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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