Reproductive Physiology Practice Questions

Q: Haploid number of chromosomes is first seen in?

Secondary spermatocyte. ***Secondary spermatocyte*** - A secondary spermatocyte is formed after **meiosis I**, where the homologous chromosomes are separated, resulting in a cell with a **haploid number of chromosomes (n)**, although each chromosome still consists of two sister chromatids. - This is the **first stage** where haploidy is achieved in spermatogenesis. - These cells are transient and quickly undergo meiosis II to form spermatids. *Spermatogonia* - Spermatogonia are **diploid (2n)** germline stem cells that undergo mitosis to produce more spermatogonia or differentiate into primary spermatocytes. - They contain the full complement of chromosomes found in somatic cells. *Primary spermatocytes* - Primary spermatocytes are also **diploid (2n)** cells that enter meiosis I. - Before meiosis I, DNA replication occurs, so each chromosome consists of two sister chromatids, but the cell still maintains a diploid chromosome number. *Spermatids* - Spermatids are formed after **meiosis II** from secondary spermatocytes and are also **haploid (n)**. - However, secondary spermatocytes become haploid **earlier** in the process, immediately following the reductional division of meiosis I.

Q: What is the average progressive velocity of human sperm under standard laboratory conditions?

1-3 mm/min. ***1-3 mm/min*** - The typical average progressive velocity of human sperm, categorized as **Grade A (rapid progressive)** motility, ranges from **25 micrometers/second or faster**, which translates to approximately 1-3 mm/minute. - This velocity is crucial for sperm to traverse the female reproductive tract and reach the ovum for fertilization. *4-6 mm/min* - This velocity range is significantly faster than the **average progressive velocity** observed in viable human sperm under standard laboratory conditions. - While some individual sperm may achieve higher speeds, this range is not representative of the **average progressive motility** of a healthy sperm population. *6-9 mm/min* - This progressive velocity is exceptionally high and not typically observed as the average for human sperm, even for highly motile sperm. - Such a high velocity would indicate an **abnormally fast movement** not compatible with biological norms for average progressive motility. *10-13 mm/min* - This range represents an extremely rapid progressive velocity for human sperm, well beyond physiological averages. - It does not align with the standard measurements for **progressive motility**, which are generally much lower.

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

Testosterone. ***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).

Q: Sertoli cells in males secrete?

MIH. ***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.

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

Granulosa cells begin to express LH receptors. ***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.

Q: Pubarche is due to?

Adrenal androgens. ***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.

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

Meiosis-I. ***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.

Q: Stimulation of the nerves of the pelvic parasympathetic plexus results in:

Penile erection. ***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.

Q: What hormones are secreted by the corpus luteum?

All of the options. ***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.

Q: What physiological event occurs during ovulation?

FSH increases steroid synthesis in granulosa cells.. ***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.

Question 1

Haploid number of chromosomes is first seen in?

Accepted Answer

Secondary spermatocyte

Answer

Spermatogonia

Answer

Primary spermatocytes

Answer

Spermatids

Question 2

What is the average progressive velocity of human sperm under standard laboratory conditions?

Accepted Answer

1-3 mm/min

Answer

4-6 mm/min

Answer

6-9 mm/min

Answer

10-13 mm/min

Question 3

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

Accepted Answer

Testosterone

Answer

DHT

Answer

DHEA

Answer

All of the options

Question 4

Sertoli cells in males secrete?

Accepted Answer

MIH

Answer

Testosterone

Answer

Dehydroepiandrosterone

Answer

Progesterone

Question 5

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

Accepted Answer

Granulosa cells begin to express LH receptors

Answer

Granulosa cells begin to express estrogen receptors

Answer

Theca cells begin to express androgen receptors

Answer

Granulosa cells begin to express progesterone receptors

Question 6

Pubarche is due to?

Accepted Answer

Adrenal androgens

Answer

Progesterone

Answer

Testosterone

Answer

Estrogen

Question 7

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

Accepted Answer

Meiosis-I

Answer

At mitosis

Answer

Meiosis-II

Answer

None of the options

Question 8

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

Accepted Answer

Penile erection

Answer

Contraction of the genital smooth muscle

Answer

Vasoconstriction

Answer

Constriction of the internal urethral sphincter

Question 9

What hormones are secreted by the corpus luteum?

Accepted Answer

All of the options

Answer

Progesterone

Answer

Estrogen

Answer

Inhibin

Question 10

What physiological event occurs during ovulation?

Accepted Answer

FSH increases steroid synthesis in granulosa cells.

Answer

Inhibin A levels increase.

Answer

Activin enhances FSH action on granulosa cells.

Answer

Completion of the first meiotic division of the oocyte occurs just before ovulation.

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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