Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 421: In spermatogenesis, independent assortment of paternal and maternal chromosomes occurs during-

A. Primary to secondary spermatocyte (Correct Answer)
B. Spermatogonia to primary spermatocyte
C. Secondary spermatocyte to spermatids
D. Spermatids to spermatozoa

Explanation: ***Primary to secondary spermatocyte*** - This transition involves **meiosis I**, specifically **anaphase I**, where homologous chromosomes separate and independently assort. - **Independent assortment** is the random orientation of homologous chromosome pairs at the metaphase plate in meiosis I, leading to genetic diversity. *Spermatogonia to primary spermatocyte* - This stage involves **mitotic division** and cellular growth, not meiosis. - Genetic recombination and independent assortment are characteristic of meiosis, not mitosis. *Secondary spermatocyte to spermatids* - This stage involves **meiosis II**, where sister chromatids separate. - While chromosomes align and separate, the primary event for independent assortment of homologous chromosomes occurs in meiosis I. *Spermatids to spermatozoa* - This process is called **spermiogenesis**, which is a maturation process involving morphological changes but not cell division. - No further genetic recombination or chromosome segregation occurs during this transformation.

Question 422: After how many days post-ovulation does the corpus luteum begin to regress?

A. None of the options
B. 5 days
C. 24 days
D. 10 days (Correct Answer)

Explanation: ***10 days*** - The corpus luteum begins to regress approximately **9-11 days post-ovulation** in the absence of pregnancy, making **10 days** the correct answer. - This regression, known as **luteolysis**, is triggered by declining levels of **LH** and leads to decreased production of **progesterone** and **estrogen**. - The functional regression marks the end of the luteal phase and precedes menstruation by approximately 3-4 days. *5 days* - At 5 days post-ovulation, the corpus luteum is in its **active growth phase** and approaching peak function. - **Progesterone** levels are rising to maintain the endometrium, not declining. - Regression has not yet begun at this early stage of the luteal phase. *24 days* - This timing is too late - at 24 days post-ovulation (approximately day 38 of the cycle), menstruation would have already occurred. - In a typical **28-day cycle**, menstruation begins around day 14 post-ovulation. - Such delayed regression would only occur with **pregnancy** and hCG support, preventing luteolysis. *None of the options* - This is incorrect because **10 days** is the medically accurate answer, falling within the established 9-11 day timeframe for corpus luteum regression.

Question 423: What hormone is primarily responsible for the onset of pubarche?

A. Testosterone
B. Luteinizing Hormone (LH)
C. Follicle-Stimulating Hormone (FSH)
D. Dehydroepiandrosterone (DHEA) (Correct Answer)

Explanation: ***Dehydroepiandrosterone (DHEA)*** - **DHEA** and its sulfate (DHEA-S) are **adrenal androgens** primarily responsible for the development of **pubarche**, which includes the growth of **pubic and axillary hair**. - This process is known as **adrenarche**, which often precedes gonadarche (the maturation of the gonads). *Luteinizing Hormone (LH)* - **LH** is crucial for **gonadarche**, stimulating **testosterone production** in males and ovulation in females. - While it contributes to overall pubertal development, it is not the primary hormone for the initial appearance of pubic hair. *Follicle-Stimulating Hormone (FSH)* - **FSH** also plays a key role in **gonadarche**, promoting **spermatogenesis** in males and follicle development in females. - Its primary action is on the gonads, not directly on the development of pubarche. *Testosterone* - **Testosterone** is an important androgen responsible for **secondary sexual characteristics** in males, such as muscle mass increase, deepening of the voice, and some aspects of pubic hair development. - However, the initial onset of pubarche is driven more by **adrenal androgens** like DHEA, rather than gonadal testosterone.

Question 424: When is the first polar body formed during oogenesis?

A. Second meiotic division
B. Mitosis
C. First meiotic division (Correct Answer)
D. Fertilization

Explanation: ***First meiotic division*** - The **first polar body** is extruded at the completion of the **first meiotic division** when the primary oocyte divides into a secondary oocyte and the first polar body. - This division is unequal, ensuring the secondary oocyte retains most of the cytoplasm and nutrients essential for future development. *Mitosis* - **Mitosis** is the process where oogonia (germline stem cells) proliferate to form primary oocytes *before* birth. - It results in two identical daughter cells and does not involve the formation of polar bodies. *Second meiotic division* - The **second polar body** is formed upon completion of the **second meiotic division**, which occurs *after fertilization*. - The second meiotic division is triggered when the secondary oocyte is penetrated by a sperm. *Fertilization* - **Fertilization** is the fusion of sperm and egg, which triggers the completion of the **second meiotic division** and the expulsion of the second polar body. - The first polar body has already been formed before fertilization occurs.

Question 425: What is the role of growth hormone in the early stages of spermatogenesis?

A. Promotes late division of spermatocytes
B. Stimulates early division of spermatogonia (Correct Answer)
C. Stimulates Sertoli and Leydig cells
D. Facilitates formation of acrosomes

Explanation: ***Stimulates early division of spermatogonia*** - **Growth hormone** plays a crucial permissive role in the initial stages of spermatogenesis, primarily by promoting the early **mitotic divisions of spermatogonia**. - This hormone ensures an adequate pool of spermatogonial stem cells to proceed through the later stages of sperm development. *Promotes late division of spermatocytes* - The progression from **primary spermatocytes** to **secondary spermatocytes** involves meiosis I, which is primarily regulated by **FSH** and **testosterone**, not directly by growth hormone. - Growth hormone's main impact is earlier in the proliferation phase of spermatogonia, rather than the meiotic divisions of spermatocytes. *Stimulates Sertoli and Leydig cells* - **Sertoli cells** are primarily stimulated by **FSH**, and **Leydig cells** are stimulated by **LH**, leading to **testosterone production**. - While growth hormone may indirectly influence the overall testicular environment, its direct and primary role is not the stimulation of these specific cell types. *Facilitates formation of acrosomes* - **Acrosome formation** occurs during **spermiogenesis**, the final stage of spermatid maturation. - This process is mainly dependent on **testosterone** and the intricate cellular machinery within the spermatid, with no direct or primary role specifically attributed to growth hormone.

Question 426: Which of the following changes is NOT seen during the capacitation of sperm?

A. Removal of cholesterol from the sperm membrane
B. Decreased permeability to calcium (Correct Answer)
C. Increased permeability to calcium ions
D. Increased motility

Explanation: ***Decreased permeability to calcium*** - **Capacitation** involves an **influx of calcium ions** into the sperm, which is crucial for subsequent acrosome reaction and hyperactivated motility. - Therefore, a *decrease* in calcium permeability would hinder, not facilitate, the necessary changes for fertilization. *Increased permeability to calcium ions* - This is a **characteristic event** during capacitation, as **calcium influx** triggers downstream signaling pathways. - The increased intracellular calcium is essential for the sperm to undergo the **acrosome reaction** and develop **hyperactivated motility**. *Removal of cholesterol from the sperm membrane* - **Cholesterol efflux** from the sperm plasma membrane is a key event in capacitation, making the membrane more fluid. - This increased fluidity is necessary for the **acrosome reaction** to occur, allowing the outer acrosomal membrane to fuse with the plasma membrane. *Increased motility* - During capacitation, sperm develop **hyperactivated motility**, characterized by a more vigorous and asymmetric flagellar beat. - This change in motility is essential for the sperm to navigate through the female reproductive tract and penetrate the egg's outer layers.

Question 427: Which of the following is a primary hormonal action of progesterone during the menstrual cycle?

A. Increases uterine sensitivity to oxytocin
B. Promotes secretory changes in the endometrium (Correct Answer)
C. Inhibits secretion of luteinizing hormone (LH)
D. Reduces body temperature

Explanation: ***Promotes secretory changes in the endometrium*** - **Progesterone**, produced by the **corpus luteum** after ovulation, acts on the **endometrium**, causing the uterine glands to become coiled and fill with secretions. - This prepares the **endometrium** for potential **implantation** of a fertilized egg, thickening the uterine lining and making it receptive. *Increases uterine sensitivity to oxytocin* - **Estrogen** is primarily responsible for increasing **myometrial** sensitivity to **oxytocin**, especially during late pregnancy and labor. - **Progesterone** actually tends to *decrease* uterine contractility and sensitivity to **oxytocin** to maintain pregnancy. *Inhibits secretion of luteinizing hormone (LH)* - While both **estrogen** and **progesterone** can exert **negative feedback** on the **hypothalamus** and **pituitary**, particularly at high levels, the primary role of progesterone during the **luteal phase** is to maintain the uterine lining. - The peak of **LH** secretion occurs *before* ovulation, driven by a surge in estrogens, while progesterone levels rise *after* ovulation. *Reduces body temperature* - **Progesterone** is known to have a **thermogenic effect**, causing a slight increase in **basal body temperature (BBT)** after ovulation. - This rise in **BBT** is often used as an indicator of ovulation in fertility tracking.

Question 428: Which hormone is predominantly secreted after 14 days of the menstrual cycle?

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

Explanation: ***Correct: Progesterone*** - After **ovulation**, which typically occurs around day 14 of a 28-day cycle, the ruptured follicle transforms into the **corpus luteum**. - The **corpus luteum** primarily secretes **progesterone**, which is crucial for preparing the **endometrium** for potential implantation. - Progesterone is the **predominant hormone** of the **luteal phase** (days 14-28). *Incorrect: Estrogen* - **Estrogen** levels rise significantly during the **follicular phase** (days 1-14), peaking just before ovulation. - After ovulation, **estrogen** levels decrease slightly and then rise again during the **luteal phase**, but its predominant role is earlier in the cycle. *Incorrect: LH (Luteinizing Hormone)* - **LH** experiences a surge around day 14, known as the **LH surge**, which triggers **ovulation**. - After this surge, LH levels decline and remain relatively low throughout the rest of the **menstrual cycle**, though it's essential for maintaining the **corpus luteum**. *Incorrect: FSH (Follicle-Stimulating Hormone)* - **FSH** is highest during the early **follicular phase**, stimulating the growth and development of ovarian follicles. - Its levels decrease as **estrogen** rises and remain low after ovulation, as its primary role is follicle maturation, not luteal phase events.

Question 429: Oxygen consumption increases in pregnancy by

A. 10%
B. 20% (Correct Answer)
C. 30%
D. 40%

Explanation: ***20%*** - During **pregnancy**, the maternal **metabolic rate increases** to support fetal growth and the physiological changes occurring in the mother's body. - This increased metabolic demand leads to a **rise in oxygen consumption** by approximately 20% compared to the non-pregnant state. *10%* - A 10% increase is an **underestimation** of the physiological change in oxygen consumption during pregnancy. - The demands of supporting a growing fetus and increased maternal tissue mass require a more substantial metabolic adjustment. *30%* - While oxygen consumption does increase significantly, a 30% rise is generally considered an **overestimation** of the average increase. - The typical physiological adaptation usually falls within the 15-25% range. *40%* - A 40% increase in oxygen consumption would represent an **extreme physiological demand** that is not typically observed during an uncomplicated pregnancy. - Such a drastic increase might indicate underlying pathology rather than normal adaptation.

Question 430: The role of human placental lactogen is :

A. Stimulate milk production
B. Promotes growth of breast for lactation.
C. Supports fetal growth and development. (Correct Answer)
D. Provide fetal nutrition by antagonizing the action of insulin in maternal circulation, breakdown of fats and proteins and transport of fatty acids and amino acids from maternal to fetal circulation.

Explanation: ***Supports fetal growth and development.*** - Human placental lactogen (hPL) acts as a **growth hormone** for the fetus, primarily by altering maternal metabolism to favor fetal nutrient supply. - It increases **maternal insulin resistance**, leading to higher maternal glucose and free fatty acids, which are then shunted to the fetus, supporting its growth and development. *Stimulate milk production* - **Prolactin**, secreted by the anterior pituitary, is the primary hormone responsible for stimulating milk production (lactogenesis). - While hPL has some structural similarity to growth hormone and prolactin, its primary role is not to directly stimulate milk production during pregnancy; rather, it prepares the breasts. *Promotes growth of breast for lactation.* - hPL, along with **estrogen** and **progesterone**, contributes to the **mammary gland development** during pregnancy, preparing the breasts for lactation. - However, its direct role is more about **mammary gland proliferation and differentiation** rather than initiation of milk production. *Provide fetal nutrition by antagonizing the action of insulin in maternal circulation, breakdown of fats and proteins and transport of fatty acids and amino acids from maternal to fetal circulation.* - This is a highly detailed and largely accurate description of *how* hPL supports fetal growth and development, making it a mechanism rather than the primary, concise role. - It describes the metabolic changes induced by hPL, which ultimately lead to the **support of fetal growth and development**.

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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