Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 451: Prostaglandins (PGs) in semen are secreted by?

A. Prostate
B. Seminal vesicle (Correct Answer)
C. Sperms
D. Testes

Explanation: ***Seminal vesicle*** - The **seminal vesicles** are the primary source of **prostaglandins (PGs)** in semen, contributing significantly to the seminal fluid volume. - These PGs play a crucial role in promoting **sperm motility** and facilitating fertilization. *Prostate* - The **prostate gland** primarily secretes **citrate**, **acid phosphatase**, and **prostate-specific antigen (PSA)**, which contribute to sperm activation and semen liquefaction. - It does not significantly contribute to the prostaglandin content of semen. *Sperms* - **Spermatozoa** themselves primarily contribute genetic material and are not a significant source of prostaglandin synthesis in semen. - Their main function is fertilization, not the production of accessory gland secretions. *Testes* - The **testes** are responsible for **spermatogenesis** (sperm production) and the synthesis of **androgens** like testosterone. - They do not secrete prostaglandins into the seminal fluid.

Question 452: According to some older studies, which sperm chromosome was hypothesized to be associated with faster initial motility?

A. None of the options
B. X chromosome
C. Y chromosome (Correct Answer)
D. Both same

Explanation: ***Y chromosome*** - **Older hypothesis** suggested that Y chromosome-bearing sperm might be faster due to being slightly smaller and lighter - However, **modern rigorous studies have largely debunked this theory** - The chromosomal size difference (X vs Y) represents less than 0.02% of total sperm mass, making any speed difference negligible - **Current scientific consensus**: No consistent, reproducible motility difference has been demonstrated *X chromosome* - X-bearing sperm are marginally larger due to more DNA content - Early theories suggested they were slower but more robust - **Modern evidence does not support consistent motility differences** between X and Y bearing sperm *Both same* - This actually reflects the **current scientific consensus** based on modern flow cytometry and separation studies - Most rigorous contemporary research shows no reliable motility differences between X and Y chromosome-bearing sperm - The Ericsson albumin method (based on speed separation) has been largely discredited *None of the options* - This option is incorrect as the question asks about historical hypotheses - Early studies did propose the Y chromosome theory, even though it's now considered largely inaccurate

Question 453: Which of the following hormones is primarily secreted by Leydig cells?

A. Testosterone (Correct Answer)
B. DHT
C. DHEA
D. All of the options

Explanation: ***Testosterone*** - **Leydig cells** (interstitial cells of Leydig), located adjacent to the **seminiferous tubules** in the testes, are the primary site of **testosterone synthesis** and secretion in males. - **Luteinizing hormone (LH)** from the pituitary gland stimulates these cells to produce testosterone. *DHT* - **Dihydrotestosterone (DHT)** is a more potent androgen than testosterone, but it is primarily formed from the peripheral conversion of testosterone by the enzyme **5-alpha-reductase** in target tissues (e.g., prostate, hair follicles), not directly secreted by Leydig cells in large amounts. - While testosterone is a precursor, DHT itself is not the primary hormone secreted by Leydig cells. *DHEA* - **Dehydroepiandrosterone (DHEA)** is an androgen primarily produced by the **adrenal glands**. - Although it can be a precursor to other sex hormones, it is not significantly produced or secreted by Leydig cells. *All of the options* - This option is incorrect because only **testosterone** is primarily secreted by Leydig cells. - DHT and DHEA are either primarily peripherally converted (DHT) or produced by different endocrine glands (DHEA).

Question 454: Sertoli cells in males secrete?

A. MIH (Correct Answer)
B. Testosterone
C. Dehydroepiandrosterone
D. Progesterone

Explanation: ***MIH (Müllerian Inhibiting Hormone)*** - **Sertoli cells** secrete multiple important substances, but among the given options, **Müllerian Inhibiting Hormone (MIH)**, also known as Anti-Müllerian Hormone (AMH), is the correct answer. - MIH causes the **regression of the Müllerian ducts** in male fetuses, preventing the development of female internal reproductive organs during sexual differentiation. - **Note:** Sertoli cells also secrete other important substances like **Inhibin** (negative feedback on FSH) and **Androgen Binding Protein (ABP)** (concentrates testosterone), but these are not among the options. *Testosterone* - **Testosterone** is primarily produced by the **Leydig cells** (interstitial cells) in the testes, not Sertoli cells. - While essential for male sexual development, spermatogenesis, and secondary sex characteristics, it is an **androgen** secreted by Leydig cells in response to LH stimulation. *Dehydroepiandrosterone* - **Dehydroepiandrosterone (DHEA)** is an **androgen precursor** primarily secreted by the **adrenal cortex** (zona reticularis). - It is not a secretory product of Sertoli cells in the testes. *Progesterone* - **Progesterone** is a **steroid hormone** primarily associated with the female reproductive system, particularly secreted by the corpus luteum and placenta. - It is not secreted by Sertoli cells in males.

Question 455: In the transition from a Graafian follicle to a functional corpus luteum, which of the following cellular events occurs?

A. Granulosa cells begin to express estrogen receptors
B. Granulosa cells begin to express LH receptors (Correct Answer)
C. Theca cells begin to express androgen receptors
D. Granulosa cells begin to express progesterone receptors

Explanation: ***Granulosa cells begin to express LH receptors*** - During the late follicular phase, under **FSH** stimulation, **granulosa cells** in the developing Graafian follicle acquire **LH receptors**. - This acquisition of LH receptors is essential for the transition to a corpus luteum, as it enables the **LH surge** to trigger ovulation and subsequently stimulate **luteinization** and **progesterone production** by the corpus luteum. - While the initial expression occurs before ovulation, the functional significance becomes apparent during the transformation to the corpus luteum, making this the most critical receptor-related event in this transition among the given options. *Granulosa cells begin to express estrogen receptors* - Granulosa cells already express **estrogen receptors** in early follicular stages, which are essential for their proliferation and **aromatase synthesis**. - Estrogen receptor expression is characteristic of developing follicles throughout folliculogenesis, not specifically associated with corpus luteum formation. *Theca cells begin to express androgen receptors* - **Theca cells** produce **androgen precursors** (androstenedione, testosterone) under LH stimulation during the follicular phase, which granulosa cells convert to estrogen. - While theca cells contribute to the corpus luteum (theca-lutein cells), androgen receptor expression is not the primary defining cellular event of this transition. *Granulosa cells begin to express progesterone receptors* - The corpus luteum is the major source of **progesterone** in the luteal phase, but granulosa cells do not significantly upregulate progesterone receptors as part of their luteinization. - The key functional change is the cells' ability to *produce* large amounts of progesterone in response to LH, not increased progesterone receptor expression.

Question 456: Pubarche is due to?

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

Explanation: ***Adrenal androgens*** - **Pubarche**, the first appearance of **pubic hair**, is primarily caused by **adrenal androgens** (DHEA, DHEA-S, and androstenedione). - This process is linked to **adrenarche**, the maturation of the adrenal zona reticularis, which occurs in **both males and females** typically between ages 8-13. - Adrenal androgens are the **initial and primary stimulus** for pubic hair development in both sexes, occurring before gonadal sex hormone production increases significantly. - The increase in adrenal androgens is responsible for the development of pubic and axillary hair as the first visible sign of puberty. *Testosterone* - **Testosterone** from the testes (in males) or ovaries (in females) increases later during **gonadarche** and enhances pubic hair growth. - However, testosterone is **not the primary cause** of pubarche; it augments hair growth that was initiated by adrenal androgens. - Pubarche typically precedes the major rise in gonadal sex hormones. *Progesterone* - **Progesterone** is primarily involved in the menstrual cycle, pregnancy maintenance, and endometrial preparation. - It has **no direct role** in stimulating pubic hair development. *Estrogen* - **Estrogen** is responsible for female secondary sexual characteristics like breast development (thelarche), but does not stimulate pubic hair growth. - Pubic hair development is an **androgen-dependent** process, not estrogen-dependent.

Question 457: Stimulation of the nerves of the pelvic parasympathetic plexus results in:

A. Contraction of the genital smooth muscle
B. Penile erection (Correct Answer)
C. Vasoconstriction
D. Constriction of the internal urethral sphincter

Explanation: ***Penile erection*** - The **pelvic splanchnic nerves** (parasympathetic) innervate the penile erectile tissues, leading to the release of **nitric oxide**. - **Nitric oxide** causes relaxation of smooth muscle in the arteries supplying the penis, leading to increased blood flow and engorgement of the cavernous spaces, resulting in erection. *Vasoconstriction* - **Vasoconstriction** is primarily mediated by the **sympathetic nervous system** through the release of norepinephrine, causing smooth muscle contraction in blood vessel walls. - The **parasympathetic nervous system** generally promotes vasodilation in specific organs like the penis, rather than widespread vasoconstriction. *Contraction of the genital smooth muscle* - While some genital smooth muscle contraction (e.g., during emission and ejaculation) involves the nervous system, **erection** specifically requires relaxation of vascular smooth muscle. - Contraction of the **bulbospongiosus** and **ischiocavernosus muscles** (skeletal muscles) helps maintain erection and contributes to ejaculation, but this is distinct from direct parasympathetic smooth muscle contraction needed for erection itself. *Constriction of the internal urethral sphincter* - **Constriction of the internal urethral sphincter** is mediated by the **sympathetic nervous system** during ejaculation to prevent retrograde ejaculation into the bladder. - The **parasympathetic nervous system** is primarily involved in bladder emptying (micturition) by relaxing the internal sphincter and contracting the detrusor muscle.

Question 458: During spermatogenesis, the number of chromosomes reduces to haploid at:

A. At mitosis
B. Meiosis-II
C. Meiosis-I (Correct Answer)
D. None of the options

Explanation: ***Meiosis-I*** - **Meiosis I** is known as the **reductional division** because it is during this stage that homologous chromosomes separate, leading to a reduction in the chromosome number from diploid (2n) to haploid (n) in each daughter cell. - This separation ensures that each secondary spermatocyte receives one chromosome from each homologous pair, thus having a **haploid set of chromosomes** (n chromosomes, each with two chromatids). *At mitosis* - **Mitosis** is a process of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, preserving the **diploid number (2n)**. - This process is used for growth and repair, not for reducing the chromosome number to haploid. *Meiosis-II* - **Meiosis II** is an **equational division**, meaning it separates the sister chromatids of the haploid cells formed during Meiosis I, similar to mitosis. - The chromosome number remains haploid (n) throughout Meiosis II; it does not further reduce the chromosome number. *None of the options* - This option is incorrect because **Meiosis-I** specifically serves the function of reducing the chromosome number to haploid during gamete formation.

Question 459: What hormones are secreted by the corpus luteum?

A. Progesterone
B. Estrogen
C. Inhibin
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - The **corpus luteum** is a temporary endocrine structure that forms from the ruptured follicle after ovulation. - It functions as an **endocrine gland** secreting multiple hormones essential for the luteal phase and early pregnancy. - The corpus luteum secretes **all three hormones listed**: progesterone, estrogen, and inhibin. **Hormonal Secretions of Corpus Luteum:** **Progesterone (Primary hormone)** - The corpus luteum is the **main source** of progesterone during the luteal phase. - Essential for **endometrial preparation** and maintenance of early pregnancy. - Prepares the endometrium for implantation and supports decidualization. **Estrogen (Secondary secretion)** - The corpus luteum continues to secrete **estrogen** in significant amounts during the luteal phase. - Works synergistically with progesterone to maintain the **endometrium**. - Lower levels than follicular phase but still physiologically important. **Inhibin (Regulatory hormone)** - The corpus luteum secretes **inhibin A** during the luteal phase. - Provides **negative feedback** to the anterior pituitary, suppressing FSH secretion. - Prevents recruitment of new follicles during the luteal phase. *Why individual options are incomplete:* - Selecting only "Progesterone," "Estrogen," or "Inhibin" would be factually correct but incomplete, as the question asks "What hormones" (plural), implying all hormones secreted should be identified.

Question 460: What physiological event occurs during ovulation?

A. Inhibin A levels increase.
B. FSH increases steroid synthesis in granulosa cells. (Correct Answer)
C. Activin enhances FSH action on granulosa cells.
D. Completion of the first meiotic division of the oocyte occurs just before ovulation.

Explanation: ***FSH increases steroid synthesis in granulosa cells.*** - During the **periovulatory period**, FSH continues to support **estrogen synthesis** in granulosa cells of the dominant follicle. - While FSH levels peak in the **mid-follicular phase**, FSH (along with the LH surge) maintains steroidogenic activity through ovulation. - Among the given options, this represents the most relevant ongoing physiological process during ovulation, though the primary event is follicular rupture and oocyte release. *Completion of the first meiotic division of the oocyte occurs just before ovulation.* - The **LH surge** triggers completion of **meiosis I** approximately **36-38 hours before ovulation**, forming a secondary oocyte and first polar body. - This event occurs **prior to** ovulation, not during it. At ovulation, the **secondary oocyte** (arrested in **metaphase II**) is released. - Meiosis II is only completed if **fertilization** occurs. *Inhibin A levels increase.* - **Inhibin A** levels rise significantly **after ovulation** during the **luteal phase**, produced by the corpus luteum. - Around ovulation, **inhibin B** is more prominent, while inhibin A remains relatively low. *Activin enhances FSH action on granulosa cells.* - **Activin** enhances FSH action throughout the **follicular phase**, promoting follicular growth and estrogen production. - This is a continuous regulatory mechanism, not a specific event occurring during ovulation itself.

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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