Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 411: What is the correct sequential order of sperm formation? 1. Spermatogonia 2. Spermatocyte 3. Spermatids 4. Spermatozoa

A. 2314
B. 3214
C. 1234 (Correct Answer)
D. 3124

Explanation: **1234** - The correct order of sperm formation begins with **spermatogonia**, which are germline stem cells that differentiate into **spermatocytes**. - Spermatocytes then undergo meiosis to become **spermatids**, which finally mature into **spermatozoa** (mature sperm). *2314* - This order is incorrect because it places spermatocytes before spermatogonia and then incorrectly places spermatogonia before spermatids. - **Spermatogonia** are the initial stem cells, preceding spermatocytes in the process. *3214* - This sequence is incorrect as it starts with spermatids, which are an intermediate stage, not the beginning of sperm formation. - **Spermatocytes** develop from spermatogonia and precede spermatids. *3124* - This order incorrectly places spermatids before spermatocytes in the sequence of maturation. - **Spermatocytes** are the cells that undergo meiosis to form spermatids.

Question 412: Which hormone maintains the endometrium during the early stages of pregnancy until the placenta assumes this role?

A. Estrogen
B. Progesterone (Correct Answer)
C. Luteinizing hormone (LH)
D. Follicle-stimulating hormone (FSH)

Explanation: ***Progesterone*** - **Progesterone** is crucial for maintaining the **endometrial lining** during early pregnancy, making it suitable for implantation and supporting the developing embryo. - Initially produced by the **corpus luteum**, it continues this role until the placenta develops sufficiently to take over progesterone production around 7-9 weeks of gestation. *Estrogen* - **Estrogen** plays a role in the growth of the **uterus** and **breast tissue** during pregnancy, but it is not the primary hormone for maintaining the endometrial lining itself. - High levels of **estrogen** are also responsible for some pregnancy symptoms like **nausea** and **mood swings**. *Luteinizing hormone (LH)* - **LH** is primarily involved in **ovulation** and the initial formation of the **corpus luteum**. - Once ovulation has occurred and the corpus luteum is formed, its direct role in maintaining the endometrium during pregnancy is minimal. *Follicle-stimulating hormone (FSH)* - **FSH** is responsible for the **recruitment and maturation of ovarian follicles** prior to ovulation. - Its levels are generally suppressed during pregnancy because the growing fetus and placenta produce other hormones that inhibit FSH release.

Question 413: A 28-year-old male presents with infertility. Which process in spermatogenesis is MOST COMMONLY impaired in male infertility?

A. Spermiation
B. Spermatocytogenesis (Correct Answer)
C. Spermiogenesis
D. Spermatogonia mitosis

Explanation: ***Spermatocytogenesis*** - This process involves the **meiotic divisions** of primary spermatocytes into secondary spermatocytes and then into spermatids. - **Meiotic defects** are among the most common causes of severe male infertility, particularly in cases of non-obstructive azoospermia and severe oligozoospermia. - Impairments include **meiotic arrest**, chromosomal abnormalities, and errors in recombination, leading to abnormal or absent sperm production. *Spermiation* - **Spermiation** is the final step where mature spermatids are released from the Sertoli cells into the lumen of the seminiferous tubules. - While essential, isolated defects in spermiation are less frequently identified as the primary cause of infertility compared to problems in earlier developmental stages. *Spermiogenesis* - **Spermiogenesis** is the morphological transformation of spermatids into mature spermatozoa. - Defects in this process commonly lead to teratozoospermia (abnormal sperm morphology), but meiotic failures in spermatocytogenesis typically result in more severe impairment of sperm production. *Spermatogonia mitosis* - **Spermatogonia mitosis** involves the proliferation of spermatogonial stem cells to maintain the germ cell pool and produce primary spermatocytes. - Complete failure of spermatogonial mitosis would lead to Sertoli cell-only syndrome, which is less common than meiotic defects affecting spermatocyte development.

Question 414: Where does meiosis occur in human females?

A. In the adult ovary (Correct Answer)
B. At birth in the ovary
C. In the adult testis
D. In the prepubertal testis

Explanation: ***In the adult ovary*** - **Meiosis I** in oocytes starts during fetal development but arrests in prophase I. It resumes and completes in the **adult ovary** just before ovulation in response to hormonal signals. - **Meiosis II** begins after the completion of Meiosis I and arrests in metaphase II. It is only completed upon **fertilization** by a sperm, also occurring within the adult reproductive tract. *At birth in the ovary* - At birth, female ovaries contain primary oocytes that have entered **meiosis I** but are arrested in prophase I; actual meiotic divisions promoting maturation do not occur at this stage. - The completion of meiosis I and the initiation of meiosis II are processes that are **post-puberty** and occur in response to hormonal changes leading to ovulation. *In the adult testis* - The testis is the male gonad, and it is the site of **spermatogenesis**, the process of sperm production involving meiosis in males. - **Oogenesis**, the formation of female gametes, occurs exclusively in the **ovaries** of females. *In the prepubertal testis* - In the prepubertal testis, spermatogenesis has not yet begun, and thus **meiosis does not occur** at this stage in males. - Meiosis in males usually begins during **puberty** under the influence of hormones like testosterone.

Question 415: Which cells are primarily responsible for the secretion of testosterone?

A. Leydig’s cells. (Correct Answer)
B. Somatotropic cells.
C. Acidophilic cells.
D. Gonadotropic cells.

Explanation: ***Leydig’s cells.*** - **Leydig cells**, located in the interstitial tissue of the testes, are the primary cells responsible for the production and secretion of **testosterone** in response to luteinizing hormone (LH). - These cells contain enzymes necessary for the synthesis of **steroid hormones**, including testosterone. *Somatotropic cells.* - **Somatotropic cells** are found in the anterior pituitary gland and primarily produce **growth hormone (GH)**. - Their function is to regulate growth and metabolism, not to produce sex hormones. *Acidophilic cells.* - **Acidophilic cells** (also called acidophils) are a type of cell in the anterior pituitary gland, which include both somatotropic cells (secreting GH) and lactotropic cells (secreting **prolactin**). - They are named for their staining properties with acidic dyes and do not directly secrete testosterone. *Gonadotropic cells* - **Gonadotropic cells** are located in the anterior pituitary gland and produce **gonadotropins**, namely luteinizing hormone (LH) and follicle-stimulating hormone (FSH). - These hormones regulate gonadal function but do not directly secrete sex hormones; instead, they stimulate the gonads (like Leydig cells) to do so.

Question 416: After ejaculation, semen liquefies in:

A. 10 minutes
B. 75 minutes
C. 120 minutes
D. 30 minutes (Correct Answer)

Explanation: ***30 minutes*** - Normal semen typically **liquefies** within **15 to 30 minutes** after ejaculation due to the action of enzymes, primarily prostatic-specific antigen (PSA), which break down the seminal coagulum. - This liquefaction is crucial for sperm motility and subsequent fertilization as it allows the sperm to become motile and advance into the female reproductive tract. *10 minutes* - While initial liquefaction may begin earlier, complete liquefaction within **10 minutes** is generally considered too rapid and could indicate an underlying issue, such as **prostatitis**. - Rapid liquefaction might signify a deficient formation of the seminal coagulum, which is essential to protect sperm immediately after ejaculation. *75 minutes* - If semen takes **longer than 60 minutes** to liquefy, it is termed **delayed liquefaction**, which can impair sperm motility and viability. - Delayed liquefaction can be a cause of male infertility and may point to issues such as seminal vesicle or prostatic dysfunction. *120 minutes* - Liquefaction after **120 minutes** is severely delayed and abnormal, significantly hindering **sperm movement** and thus reducing the chances of conception. - Such prolonged liquefaction times often warrant further diagnostic investigation into the functionality of the male accessory glands.

Question 417: What is the average velocity of sperm in millimeters per minute?

A. 1-2 cm/hr
B. 2-4 cm/min
C. 1-4 mm/min (Correct Answer)
D. 1-4 mm/hr

Explanation: ***1-4 mm/min*** - The typical average velocity of human sperm in the female reproductive tract is estimated to be between **1 to 4 millimeters per minute**. - This speed allows them to navigate through the cervix and uterus towards the fallopian tubes, crucial for fertilization. *1-2 cm/hr* - This rate is significantly **slower** than the observed average velocity of sperm within the female reproductive tract. - Converting 1-2 cm/hr to mm/min yields approximately 0.17-0.33 mm/min, which is too low. *2-4 cm/min* - This velocity is much **faster** than the actual average speed of sperm. - Converting 2-4 cm/min to mm/min yields 20-40 mm/min, which would be an unrealistically high speed for sperm in vivo. *1-4 mm/hr* - This rate is too **slow** for effective sperm motility to reach the ovum within a reasonable timeframe for fertilization. - This velocity would translate to only 0.017-0.067 mm/min, indicating a mobility impairment.

Question 418: In which phase of the sexual response cycle does the erection of the penis occur?

A. Arousal phase (Correct Answer)
B. Plateau phase
C. Orgasm phase
D. Resolution phase

Explanation: ***Arousal phase*** - The **arousal phase** (or excitement phase) is the initial stage of the sexual response cycle, characterized by **vasocongestion** leading to penile erection in males. - During this phase, physiological changes such as increased heart rate, blood pressure, and muscle tension begin to occur, preparing the body for sexual activity. *Plateau phase* - The **plateau phase** follows arousal and is marked by intensified physiological responses, but the primary **erection** usually occurs during the arousal phase. - This phase involves further increases in muscle tension, heart rate, and deeper breathing, maintaining but typically not initiating penile erection. *Orgasm phase* - The **orgasm phase** is the peak of sexual arousal, involving rhythmic muscle contractions and the release of sexual tension. - While erection is crucial for achieving orgasm, the erection itself occurs well before this stage, as part of the initial arousal. *Resolution phase* - The **resolution phase** is the return of the body to its pre-aroused state, during which physiological responses subside and **erection is lost**. - This phase occurs after orgasm and is characterized by a refractory period in males.

Question 419: What is the shortest phase of the sexual cycle?

A. Excitement phase
B. Plateau phase
C. Orgasm phase (Correct Answer)
D. Resolution phase

Explanation: ***Orgasm phase*** - The **orgasm phase** is characterized by a rapid, intense physiological release, typically lasting only a few seconds. - It is the peak of sexual arousal and involves involuntary muscle contractions and a surge of pleasure. *Excitement phase* - The **excitement phase** is the initial stage of sexual arousal, which can last from minutes to several hours. - It involves physiological changes like increased heart rate, blood flow to genitals, and muscle tension. *Plateau phase* - The **plateau phase** follows the excitement phase and can last for several minutes. - During this phase, sexual tension intensifies, leading to further physiological changes such as increased heart rate, breathing, and blood pressure, often leading directly into orgasm. *Resolution phase* - The **resolution phase** is the post-orgasmic period where the body returns to its unaroused state. - This phase typically lasts longer than the orgasm phase, as blood flow and muscle tension gradually subside.

Question 420: Red cell volume is increased by what percentage in pregnancy?

A. 10 - 20%
B. 20 - 30% (Correct Answer)
C. 30 - 40%
D. 40 - 50%

Explanation: ***20 - 30%*** - During pregnancy, **red cell volume** increases by approximately **20-30%** (250-450 mL increase) to meet the increased oxygen demands of the mother and fetus. - However, **plasma volume** increases by a greater proportion (**40-50%**), leading to a dilutional anemia often referred to as **physiologic anemia of pregnancy**. - This disproportionate increase causes a fall in hemoglobin concentration and hematocrit despite the absolute increase in red cell mass. *10 - 20%* - An increase of **10-20%** in red cell volume during pregnancy would be considered **insufficient** for meeting the metabolic demands. - This range is at the lower end of the normal physiological adaptation and could suggest a **suboptimal erythropoietic response**. *30 - 40%* - While a significant increase in red cell volume occurs, **30-40%** is generally higher than the average physiological increase observed. - This percentage more closely reflects the **plasma volume increase** rather than the red cell volume increase. *40 - 50%* - An increase of **40-50%** in red cell volume during pregnancy would be considered **excessive** and outside the normal physiological range. - This percentage actually represents the typical **plasma volume increase**, not the red cell volume increase.

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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