Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 381: Gonadotropin levels decline to prepubertal levels by age

A. 3 years to 4 years of age.
B. 6 month to 1 year of age. (Correct Answer)
C. 1 year to 2 years of age.
D. 2 years to 3 years of age.

Explanation: ***6 months to 1 year of age*** * Following the **"mini-puberty" of infancy** (where gonadotropin levels surge in the first few months of life), LH and FSH levels progressively decline and typically reach **prepubertal nadir levels by 6-12 months of age**. * This represents the completion of the transitional decline from the neonatal gonadotropin surge to the quiescent prepubertal state. * Most current pediatric endocrinology references cite this timeframe as when gonadotropin levels stabilize at their lowest prepubertal values. *1 year to 2 years of age* * By this age, gonadotropin levels have **already declined** to prepubertal levels and are in a sustained quiescent phase. * This period represents the **maintenance** of low gonadotropin levels rather than the active decline period from infancy. * The initial nadir is typically reached earlier, during the first year of life. *2 years to 3 years of age* * Gonadotropin levels remain at prepubertal nadir during this period, having completed their decline much earlier. * This is part of the prolonged prepubertal quiescence that continues until pubertal activation begins years later. *3 years to 4 years of age* * Similar to 2-3 years, this represents a period of sustained **prepubertal quiescence** with stable low gonadotropin levels. * The decline from neonatal levels occurred years earlier, typically within the first year of life.

Question 382: Sperm acquires motility in:

A. Seminal vesicle
B. Ejaculatory duct
C. Epididymis (Correct Answer)
D. Testes

Explanation: ***Correct Answer: Epididymis*** - Sperm mature and acquire **motility** and the ability to fertilize an egg during their transit through the epididymis. - This process is known as **sperm maturation** or **epididymal maturation**, involving changes in sperm ultrastructure, metabolism, and surface molecules. - The epididymis also serves as the primary site for **sperm storage**. *Incorrect: Seminal vesicle* - The seminal vesicles produce a fluid rich in **fructose** (energy for sperm), prostaglandins, and clotting proteins, which contributes to semen volume but does not impart motility. - Seminal vesicles are **glands that secrete fluid**; they do not store sperm. *Incorrect: Ejaculatory duct* - The ejaculatory ducts are formed by the union of the vas deferens and the seminal vesicle ducts; their primary role is to **transport sperm** and seminal fluid into the urethra during ejaculation. - Sperm already possess motility by the time they reach this duct from the epididymis. *Incorrect: Testes* - Sperm are produced in the **seminiferous tubules** of the testes through a process called spermatogenesis. - Newly formed spermatozoa in the testes are **non-motile** and unable to fertilize an ovum.

Question 383: At the time point indicated by the arrow, the hormone levels are:

A. Decreased estrogen, increased progesterone
B. Increased estrogen, increased progesterone
C. Decreased estrogen, decreased progesterone
D. Increased estrogen, decreased progesterone (Correct Answer)

Explanation: ***Increased estrogen, decreased progesterone*** - The arrow (red circle) points to Day 14, marking the approximate time of **ovulation**. At this point, the graph shows that **estrogen levels peak** just before ovulation and begin to decrease during ovulation. - Progesterone levels are relatively **low** during the follicular phase and only start to significantly increase **after ovulation** as the corpus luteum forms. *Decreased estrogen, increased progesterone* - This hormonal profile is characteristic of the **mid to late luteal phase**, not ovulation. - During the luteal phase, post-ovulation, the **corpus luteum** predominantly produces **progesterone**, leading to its increase, while estrogen levels decline from their pre-ovulatory peak. *Increased estrogen, increased progesterone* - While estrogen is high just before ovulation, **progesterone remains low** until after ovulation. - An increase in both significant progesterone and estrogen would be more indicative of the middle of the **luteal phase** when the corpus luteum is fully functional and producing both hormones in higher amounts. *Decreased estrogen, decreased progesterone* - This hormone profile typically occurs at the **very end of the luteal phase** if pregnancy does not occur, leading to the breakdown of the corpus luteum and subsequent menstruation. - It also characterizes the early follicular phase, not the time around ovulation.

Question 384: Sertoli cells secrete ?

A. Androgen
B. FSH
C. Testosterone
D. Inhibin (Correct Answer)

Explanation: ***Inhibin*** - **Sertoli cells** secrete **inhibin**, a hormone that selectively inhibits the secretion of **FSH** from the anterior pituitary. - Inhibin plays a crucial role in the **negative feedback loop** regulating spermatogenesis. *Androgen* - **Leydig cells**, not Sertoli cells, are responsible for producing and secreting **androgens**, primarily testosterone. - Androgens are essential for the development of male secondary sexual characteristics and spermatogenesis. *FSH* - **FSH** (Follicle-Stimulating Hormone) is secreted by the **anterior pituitary gland**, not by Sertoli cells. - FSH acts on Sertoli cells to stimulate spermatogenesis. *Testosterone* - **Testosterone** is the primary androgen produced by the **Leydig cells** in the testes. - Sertoli cells respond to testosterone, but they do not secrete it; instead, they convert some of it to estrogen and dihydrotestosterone.

Question 385: A major function of the epididymis is:

A. Storage and transport of mature sperm (Correct Answer)
B. Secretion of estrogens
C. Initiating the development of spermatozoa
D. Production of inhibin

Explanation: ***Storage and transport of mature sperm*** - The epididymis is a highly convoluted tubule where **sperm mature** and gain motility over several weeks. - It also serves as a **storage site** for these mature sperm until ejaculation. *Secretion of estrogens* - **Estrogens** are primarily produced by the **ovaries** in females and, to a lesser extent, by the adrenal glands and testes. - The epididymis does not have a significant role in estrogen secretion. *Initiating the development of spermatozoa* - The initiation and primary development of spermatozoa, known as **spermatogenesis**, occurs in the **seminiferous tubules** of the testes. - The epididymis is responsible for further maturation and storage, not initial development. *Production of inhibin* - **Inhibin** is a hormone primarily produced by the **Sertoli cells** in the seminiferous tubules of the testes. - Its main function is to selectively inhibit the secretion of **follicle-stimulating hormone (FSH)** from the anterior pituitary.

Question 386: Spermatogenesis occurs at which temperature condition?

A. Temperature does not play a role
B. Temperature lower than core body temperature (Correct Answer)
C. Temperature higher than core body temperature
D. Body temperature

Explanation: ***Temperature lower than core body temperature*** - Spermatogenesis, the process of sperm production, is **temperature-sensitive** and requires a cooler environment than the core body temperature. - The **scrotum** is located outside the abdominal cavity, providing a temperature that is typically 2-3°C lower than the core body temperature, which is optimal for sperm development. *Temperature does not play a role* - This statement is incorrect as temperature plays a crucial role in spermatogenesis; **elevated temperatures can impair sperm production** and function. - Testicular function, including germ cell development, is highly sensitive to heat stress. *Temperature higher than core body temperature* - A temperature higher than core body temperature would be **detrimental to spermatogenesis**, leading to reduced sperm viability and quantity. - Exposure to high temperatures, such as through cryptorchidism (undescended testes), can cause **infertility**. *Body temperature* - If spermatogenesis were to occur at core body temperature, the quality and quantity of sperm would be **significantly reduced**, potentially leading to infertility. - The evolutionary advantage of the testes being located in the scrotum is precisely to maintain this **optimal cooler temperature**.

Question 387: First sign of pubertal development in a female is ?

A. Appearance of pubic hair
B. Maximum growth velocity
C. Breast enlargement (Correct Answer)
D. Onset of menstruation

Explanation: ***Breast enlargement*** - Breast budding, known as **thelarche**, is typically the **first noticeable sign** of puberty in females, usually occurring between ages 8 and 13. - This development is driven by **estrogen** and marks the beginning of the stages of breast development. *Enlargement of pubic hair* - The appearance of **pubic hair**, known as **pubarche** or **adrenarche**, typically follows thelarche by several months. - While an early sign, it usually appears *after* breast development has begun. *Maximum growth velocity* - The period of **maximum growth velocity** (peak height velocity) usually occurs around **Tanner stage 3 or 4** of puberty. - This growth spurt follows the initial hormonal changes that trigger breast development and the emergence of pubic hair. *Onset of menstruation* - The **onset of menstruation (menarche)** is a *later* event in female pubertal development, typically occurring about **2 to 2.5 years after thelarche**. - It signifies the maturation of the reproductive system and the presence of regular ovulatory cycles.

Question 388: Which of the following is not secreted by Sertoli cells?

A. Inhibin
B. Follistatin
C. Activin
D. Relaxin (Correct Answer)

Explanation: ***Relaxin*** - **Sertoli cells** do not secrete relaxin; it is primarily produced in the **corpus luteum** during pregnancy to relax the pelvic ligaments and cervix. - In males, a small amount of relaxin is produced by the **prostate gland**, contributing to sperm motility. *Inhibin* - **Sertoli cells** secrete inhibin, which negatively regulates **FSH** secretion from the anterior pituitary, providing feedback control for spermatogenesis. - **Inhibin** acts to suppress the synthesis and release of **FSH** in the pituitary gland. *Follistatin* - **Sertoli cells** secrete follistatin, a protein that binds to and inhibits the activity of **activin**, and to a lesser extent, activin-like proteins such as **BMPs**. - Its main role is to regulate the bioavailability and signaling of members of the **TGF-β superfamily**. *Activin* - **Sertoli cells** secrete activin, which generally stimulates **FSH** secretion and *spermatogenesis*, acting in opposition to inhibin. - **Activin** is a dimer composed of two β subunits and has various roles in reproduction, immunology, and inflammation.

Question 389: Order of development of secondary sexual characteristic in male –

A. Testicular development –beard–pubic hair–axillary hair
B. Axillary hair–beard –pubic hair–testicular development
C. Pubic hair–testicular development–axillary hair – beard
D. Testicular development–pubic hair–axillary hair–beard (Correct Answer)

Explanation: ***Testicular development–pubic hair–axillary hair–beard*** - The first sign of puberty in males is typically an increase in **testicular size**, followed by the appearance of **pubic hair**. - **Axillary hair** usually develops after pubic hair, and the development of a **beard** or facial hair is one of the later secondary sexual characteristics. *Testicular development –beard–pubic hair–axillary hair* - This order incorrectly places **beard growth** and **axillary hair** before **pubic hair**, which is typically the second sign of male puberty. - While testicular development is indeed first, the subsequent sequence of hair development is incorrect. *Axillary hair–beard –pubic hair–testicular development* - This order is incorrect because **testicular development** is the initial event of male puberty, not a later one. - Additionally, both **axillary hair** and **beard growth** typically follow pubic hair development, not precede it. *Pubic hair–testicular development–axillary hair – beard* - This order incorrectly places **pubic hair** development before **testicular development**, which is the primary and earliest sign of puberty in males. - While the sequence of other hair development is later, the initial stage is incorrect.

Question 390: Sertoli cells play a key role in which of the following processes?

A. Spermiogenesis (Correct Answer)
B. Gonadogenesis
C. Secretion of seminal fluid
D. Testosterone secretion

Explanation: ***Spermiogenesis*** - **Sertoli cells** are crucial for supporting and nourishing developing **spermatids** during their maturation into spermatozoa, a process known as spermiogenesis. - They form the **blood-testis barrier**, which protects germ cells from immune attack and provides a unique microenvironment necessary for this process. *Gonadogenesis* - **Gonadogenesis** is the formation and development of the gonads (testes or ovaries). While Sertoli cells differentiate during male gonadogenesis, they are not the primary drivers of this broader developmental process. - This process involves the differentiation of primordial germ cells and somatic cells, influenced by various genetic and hormonal factors. *Secretion of seminal fluid* - **Seminal fluid** is primarily secreted by accessory glands such as the **seminal vesicles**, **prostate gland**, and **bulbourethral glands**. - Sertoli cells do not directly contribute to the bulk of seminal fluid, although they secrete a fluid component within the seminiferous tubules. *Testosterone secretion* - **Testosterone** is primarily secreted by the **Leydig cells** (also known as interstitial cells of Leydig), which are located in the connective tissue between the seminiferous tubules. - While Sertoli cells produce **androgen-binding protein** that helps maintain high local testosterone concentrations, they do not synthesize testosterone themselves.

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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