Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 431: Testes are not palpable in

A. SRY deletion (Correct Answer)
B. DAX 1 deletion
C. WNT- 4 gene mutation
D. RSPO-1 gene mutation

Explanation: ***SRY deletion*** - **SRY (Sex-determining Region Y) gene** is the master regulator of male sex determination on the Y chromosome; its deletion in 46,XY individuals results in **Swyer syndrome** (pure gonadal dysgenesis). - Without functional SRY, **testes fail to develop entirely**, and the gonads remain as non-functional **streak gonads** rather than differentiating into either testes or ovaries. - Result: **No palpable testes** because testicular tissue never forms; individuals develop female external genitalia despite XY karyotype. *DAX1 deletion* - DAX1 (NR0B1) normally **antagonizes testicular development** and supports adrenal/gonadal development. - **Deletion of DAX1** would actually **reduce anti-testis effects**, allowing testicular development to proceed more readily if SRY is present. - DAX1 **duplications** (not deletions) can impair male development; deletions cause **adrenal hypoplasia congenita** but do not prevent testicular formation. *WNT-4 gene mutation* - **WNT4** promotes **ovarian development** and opposes male differentiation pathways in normal female development. - **Loss-of-function mutations** in WNT4 do not prevent testicular development in 46,XY individuals where SRY is present and functional. - WNT4 overexpression (not loss-of-function mutation) could theoretically interfere with male development, but standard WNT4 mutations do not cause absent testes. *RSPO-1 gene mutation* - **RSPO1** (R-spondin 1) enhances **Wnt/β-catenin signaling** and supports ovarian differentiation; primarily relevant in 46,XX sex development. - Loss-of-function mutations in RSPO1 lead to **46,XX testicular/ovotesticular DSD**, where testicular tissue develops inappropriately in XX individuals. - In 46,XY individuals with functional SRY, RSPO1 mutations would **not prevent testicular development**, so testes would be palpable.

Question 432: Antimullerian hormone is secreted by ?

A. Theca cells
B. Leydig cells
C. Both Sertoli cells and granulosa cells (Correct Answer)
D. None of the above

Explanation: ***Both Sertoli cells and granulosa cells*** - **Antimullerian hormone (AMH)** is produced by **Sertoli cells in males** and **granulosa cells in females** - In **males**: Sertoli cells secrete AMH during fetal development to cause **regression of Müllerian ducts** (which would otherwise develop into uterus, fallopian tubes, and upper vagina) - In **females**: Granulosa cells of developing ovarian follicles secrete AMH, which serves as a **marker of ovarian reserve** and inhibits excessive follicle recruitment - This is the only option that correctly identifies both cell types that produce AMH *Theca cells* - Theca cells are found in ovarian follicles and produce **androgens** (androstenedione and testosterone), not AMH - These androgens are converted to estrogens by granulosa cells via aromatase enzyme - Theca cells do not produce antimullerian hormone *Leydig cells* - Leydig cells are located in the **testes** and produce **testosterone** - They do not produce antimullerian hormone - Only Sertoli cells (not Leydig cells) produce AMH in males *None of the above* - This is incorrect because AMH is indeed produced by specific cell types: **Sertoli cells in males** and **granulosa cells in females**

Question 433: Which hormone is primarily responsible for galactopoiesis?

A. Growth hormone
B. Insulin
C. Oxytocin
D. Prolactin (Correct Answer)

Explanation: ***Prolactin*** - **Prolactin** is the primary hormone responsible for **galactopoiesis**, which is the maintenance of milk production after initiation. - It stimulates the **mammary epithelial cells** to synthesize and secrete milk components. *Growth hormone* - While growth hormone has some synergistic effects on milk production, it is not the **primary hormone** for galactopoiesis. - Its main roles include promoting **growth** and regulating **metabolism**. *Insulin* - **Insulin** is essential for general metabolic support and cell function, which indirectly supports milk production. - However, it does not directly stimulate the **synthesis or secretion of milk components**. *Oxytocin* - **Oxytocin** is responsible for the **milk ejection reflex** (let-down), causing milk to be released from the mammary glands. - It does not directly control the **synthesis or production** of milk itself.

Question 434: Penile erection is mediated by which system?

A. Parasympathetic system via muscarinic receptors (Correct Answer)
B. Parasympathetic system via nicotinic receptors
C. Sympathetic system via α-receptors
D. Sympathetic system via β-receptors

Explanation: ***Parasympathetic system via muscarinic receptors*** - Penile erection is primarily a **parasympathetic response** mediated by the **pelvic splanchnic nerves (S2-S4)**. - The key mechanism involves **nitric oxide (NO)** release from non-adrenergic, non-cholinergic (NANC) neurons, which activates guanylate cyclase → increases cGMP → smooth muscle relaxation in the **corpora cavernosa**. - **Acetylcholine acting on muscarinic receptors** plays a **supportive role** by enhancing NO release and contributing to vasodilation. - For exam purposes, the parasympathetic system (with its cholinergic muscarinic component) is the recognized answer. *Parasympathetic system via nicotinic receptors* - **Nicotinic receptors** are located at **autonomic ganglia** and **neuromuscular junctions**, not at the effector sites in penile vasculature. - While nicotinic transmission occurs at the parasympathetic ganglia, the post-ganglionic fibers act on **muscarinic receptors** and release **NO** at the target tissue. - This option confuses the ganglionic transmission with the effector mechanism. *Sympathetic system via α-receptors* - The **sympathetic nervous system** via **α1-adrenergic receptors** causes **vasoconstriction** and maintains penile **flaccidity** (detumescence). - Sympathetic activation is responsible for **ejaculation** and the resolution phase after orgasm. - Activation of α-receptors opposes erection by causing smooth muscle contraction. *Sympathetic system via β-receptors* - **β-adrenergic receptors** are involved in functions like **cardiac stimulation** and **bronchodilation**, but play no significant role in penile erection. - The sympathetic system's role in sexual function is primarily through **α-receptors** (detumescence and ejaculation), not β-receptors.

Question 435: Which of the following is not a component of a mature sperm cell?

A. Lysosome
B. Golgi apparatus
C. Mitochondria
D. Endoplasmic reticulum (Correct Answer)

Explanation: ***Endoplasmic reticulum*** - The **endoplasmic reticulum** is prominent in spermatogonia and spermatocytes but largely absent in **mature sperm** as organelles are shed during spermiogenesis to reduce cell volume. - Its primary functions of protein synthesis and lipid metabolism are not required in a terminally differentiated, motile cell like a mature sperm. *Golgi apparatus* - The **Golgi apparatus** reorganizes during spermiogenesis to form the **acrosome**, which is a crucial structure for fertilization. - While the distinct Golgi stacks are not present, its modified derivative, the acrosome, is an essential component. *Mitochondria* - **Mitochondria** are abundant in the midpiece of the sperm tail, arranged in a spiral sheath. - They are vital for generating the **ATP** required for the flagellum's motility, enabling the sperm to swim. *Lysosome* - Although typical lysosomes are not found, the **acrosome** of the sperm is considered a modified lysosome. - The acrosome contains **hydrolytic enzymes** similar to lysosomes, which are critical for penetrating the egg's outer layers during fertilization.

Question 436: Acrosome reaction is seen in?

A. Spermatogenesis
B. Oogenesis
C. Fertilization (Correct Answer)
D. Menstruation

Explanation: ***Fertilization*** - The **acrosome reaction** is a crucial event that occurs when a **spermatozoon** comes into contact with the **zona pellucida** surrounding the oocyte. - This reaction involves the release of **hydrolytic enzymes** from the acrosome, which are essential for the sperm to penetrate the zona pellucida and fuse with the oocyte membrane. *Spermatogenesis* - **Spermatogenesis** is the process of sperm formation in the testes, involving meiosis and spermiogenesis. - While it produces the sperm cell with an acrosome, the **acrosome reaction itself does not occur** during this developmental stage. *Oogenesis* - **Oogenesis** is the process of egg cell formation in the ovaries. - This process is entirely **separate from sperm function** and does not involve the acrosome or the acrosome reaction. *Menstruation* - **Menstruation** is the monthly shedding of the uterine lining in females when fertilization does not occur. - This process is part of the female reproductive cycle and has **no direct involvement with sperm or the acrosome reaction**.

Question 437: Labour pain in uterus is carried by

A. Sympathetic nerves (Correct Answer)
B. Pudendal nerve
C. Parasympathetic nerves
D. Splanchnic nerve

Explanation: ***Sympathetic nerves*** - Pain signals from the **uterus** during the first stage of labor (cervical dilation and uterine contractions) are transmitted via **visceral afferent fibers that accompany the sympathetic nerves** through the **hypogastric plexus**. - These fibers synapse in the **thoracolumbar spinal cord** at **T10-L1 segments**, leading to referred pain in these dermatomes. - The pathway is: Uterus → Uterine plexus → Superior hypogastric plexus → Sympathetic chain → T10-L1 dorsal roots. *Splanchnic nerve* - While visceral afferents do travel with splanchnic nerves in the thoracoabdominal region, for **uterine pain** specifically, the standard medical terminology refers to **sympathetic nerves** and the **hypogastric plexus** as the primary pathway. - Splanchnic nerves typically refer to thoracic sympathetic contributions (T5-T12) to upper abdominal viscera. *Pudendal nerve* - The **pudendal nerve (S2-S4)** primarily innervates the perineum, external genitalia, and pelvic floor structures. - It transmits pain during the **second stage of labor**, particularly with stretching of the perineum and vaginal distension, but **not from the uterus itself**. *Parasympathetic nerves* - **Parasympathetic innervation (S2-S4 via pelvic splanchnic nerves)** to the uterus influences motor function but does **not transmit nociceptive (pain) signals** during labor. - These nerves are involved in visceral reflexes and efferent control, not the primary afferent pain pathway.

Question 438: Spermatogenesis begins at -

A. Birth
B. 5 years
C. Puberty (Correct Answer)
D. 18 years

Explanation: ***Puberty*** - **Spermatogenesis**, the process of sperm production, is initiated and sustained by the surge of **gonadotropin-releasing hormone (GnRH)**, which begins at puberty. - This hormonal signal leads to the secretion of **luteinizing hormone (LH)** and **follicle-stimulating hormone (FSH)**, crucial for testicular function and sperm development. *Birth* - At birth, the male testes contain **spermatogonia**, but these cells remain dormant and do not begin active sperm production. - Hormonal levels at birth are not conducive to initiating spermatogenesis. *5 years* - While some hormonal changes occur in early childhood, they are not sufficient to trigger the full process of spermatogenesis. - The reproductive system is still in a quiescent state before puberty. *18 years* - By 18 years, spermatogenesis is typically well-established and has been ongoing for several years, having started at puberty. - This age marks a period of full reproductive maturity, not the initiation of sperm production.

Question 439: What is the primary gene responsible for gonads to testes differentiation?

A. SRY gene (Correct Answer)
B. WNT-4 gene
C. DAX1 gene
D. SOX9 gene

Explanation: ***SRY gene*** - The **SRY gene** (Sex-determining Region Y) is located on the **Y chromosome** and is the **primary master regulator** that initiates the cascade of events leading to testicular development from the undifferentiated bipotential gonad. - Its gene product, the **SRY protein**, acts as a transcription factor that directly upregulates downstream genes like **SOX9**, triggering male sex determination. *WNT-4 gene* - The **WNT-4 gene** is primarily involved in **female sex differentiation**, promoting ovarian development and actively suppressing male differentiation pathways. - Its expression is downregulated in males during gonad development, allowing testicular differentiation to proceed. *DAX1 gene* - The **DAX1 gene** (Dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on chromosome X, gene 1) is a negative regulator of male sexual differentiation. - In females, it contributes to ovarian development; overexpression in males can lead to **sex reversal** and gonadal dysgenesis. *SOX9 gene* - While **SOX9** is critical for testicular differentiation, it acts **downstream** of SRY and is not the primary initiator. - SRY activates SOX9, which then maintains testicular development through positive feedback loops and regulation of anti-Müllerian hormone (AMH).

Question 440: LH surge is associated with?

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

Explanation: ***Increased estrogen & decreased progesterone*** - The **LH surge** is triggered by a significant rise in **estrogen** levels from the dominant follicle, indicating ovarian readiness. - At the time of the LH surge, **progesterone** levels remain low; they only begin to rise significantly after ovulation, when the corpus luteum forms. *Increased estrogen & increased progesterone* - While **estrogen** levels are high, **progesterone** only significantly increases *after* ovulation, as the corpus luteum develops. - High estrogen *and* high progesterone together are typically seen in the **luteal phase**, not at the peak of the LH surge. *Decreased estrogen & increased progesterone* - A decrease in **estrogen** would suppress LH, not trigger a surge. - Increased **progesterone** would also inhibit LH release via negative feedback in the follicular phase if it were to occur pre-ovulation. *Decreased estrogen & decreased progesterone* - Both **decreased estrogen** and **decreased progesterone** would lead to low FSH/LH levels and would not promote an LH surge or ovulation. - This hormonal profile is more characteristic of the very early follicular phase or menopause.

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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