Reproductive Physiology Practice Questions

Q: Which statement is true about spermatogenesis?

It takes 74 days to complete.. ### Explanation **1. Why Option A is Correct:** Spermatogenesis is the process by which male spermatogonia develop into mature spermatozoa. In humans, the entire process—from the initial division of a spermatogonium to the release of a mature sperm cell into the lumen—takes approximately **74 days**. This timeline is a high-yield physiological constant often tested in exams. **2. Why the Other Options are Incorrect:** * **Option B:** Spermatogenesis occurs exclusively within the **seminiferous tubules** of the testes. The spermatic cord is a collection of structures (including the vas deferens and pampiniform plexus) that suspends the testis in the scrotum; it does not produce sperm. * **Option C:** Meiosis begins with the **primary spermatocyte**. The first meiotic division (reductional) converts a primary spermatocyte into two secondary spermatocytes. The second meiotic division then converts these into spermatids. * **Option D:** This is reversed. **Spermatozoa are formed from spermatids** through a process of morphological maturation called **spermiogenesis** (involving acrosome formation and tail development). **3. NEET-PG High-Yield Pearls:** * **Spermiogenesis vs. Spermatogenesis:** Spermiogenesis is specifically the transformation of a spermatid into a spermatozoon (no cell division occurs here). * **Spermiation:** The process by which mature spermatozoa are released from Sertoli cells into the seminiferous tubule lumen. * **Hormonal Control:** LH stimulates **Leydig cells** to produce testosterone; FSH stimulates **Sertoli cells** to support spermatogenesis and produce Androgen Binding Protein (ABP). * **Temperature:** Optimal spermatogenesis requires a temperature **2–3°C lower** than core body temperature.

Q: Semen examination of a man showed counts of 25 million/cu.mm, volume - 1.5 ml; motility - 15%; Morphology - 15%. What is the diagnosis?

Asthenospermia. To answer this question correctly, we must compare the patient's values against the **WHO (2010/2021) criteria** for normal semen analysis. ### **Analysis of Parameters** 1. **Sperm Count:** The patient has **25 million/ml**. The lower reference limit is **15 million/ml**. Therefore, the count is **normal**. 2. **Motility:** The patient has **15%** motility. The lower reference limit is **40%** (total motility) or **32%** (progressive motility). This is significantly **low**. 3. **Morphology:** The patient has **15%** normal forms. The lower reference limit is **4%** (Kruger’s strict criteria). Therefore, morphology is **normal**. 4. **Volume:** 1.5 ml is the lower limit of normal. ### **Why Asthenospermia is Correct** **Asthenospermia** (or Asthenozoospermia) is defined as reduced sperm motility. Since the only abnormal parameter in this patient is the low motility (15%), this is the primary diagnosis. ### **Why Other Options are Incorrect** * **Azoospermia:** Refers to the total absence of spermatozoa in the ejaculate. This patient has 25 million/ml. * **Oligospermia:** Refers to a low sperm count (<15 million/ml). This patient’s count is within the normal range. * **Teratospermia:** Refers to poor sperm morphology (<4% normal forms). This patient has 15% normal morphology, which is healthy. ### **High-Yield Clinical Pearls for NEET-PG** * **Oligoasthenoteratozoospermia (OAT):** A condition where all three variables (count, motility, and morphology) are subnormal. * **Aspermia:** Complete absence of semen (no ejaculate), not to be confused with Azoospermia. * **Hypospermia:** Semen volume <1.5 ml. * **Hematospermia:** Presence of blood in semen (commonly associated with prostatic inflammation). * **Fructose in Semen:** Produced by seminal vesicles; its absence suggests bilateral congenital absence of the vas deferens or ejaculatory duct obstruction.

Q: Serum inhibin B is secreted by ovarian granulosa cells starting at which stage?

Preantral follicle stage. **Explanation:** The secretion of Inhibin B is a key marker of follicular development and ovarian reserve. **1. Why Preantral Follicle Stage is Correct:** Inhibin B is produced by the **granulosa cells** of small, developing follicles. Its secretion begins at the **preantral (primary/secondary) follicle stage**, as soon as the granulosa cells begin to proliferate and differentiate under the initial influence of FSH. Inhibin B serves as a primary feedback regulator, suppressing FSH secretion from the anterior pituitary to ensure that only the most sensitive follicles continue to grow. **2. Analysis of Incorrect Options:** * **Primordial follicle stage:** These follicles are "resting" and consist of an oocyte surrounded by a single layer of flattened pre-granulosa cells. They are metabolically quiet and do not secrete significant amounts of inhibin. * **Early antral stage:** While Inhibin B levels peak during the early antral stage (recruitment phase), its *secretion* actually begins earlier, during the preantral transition. * **Preovulatory stage:** This stage is dominated by **Inhibin A**. While Inhibin B is the marker of the follicular phase (secreted by small follicles), Inhibin A is the marker of the luteal phase (secreted by the dominant follicle and corpus luteum). **3. High-Yield Clinical Pearls for NEET-PG:** * **Inhibin B:** Secreted by granulosa cells of **small follicles**; peaks in the **early follicular phase**. It is a marker of the *quantity* of the ovarian reserve. * **Inhibin A:** Secreted by the **dominant follicle** and **corpus luteum**; peaks in the **mid-luteal phase**. * **Clinical Use:** Low Day-3 Inhibin B levels are associated with poor response to ovulation induction and declining ovarian reserve. * **Tumor Marker:** Inhibins are used as serum markers for **Granulosa Cell Tumors** of the ovary.

Q: Which of the following is NOT a function of estrogen?

Stimulation of secretory function on the endometrium. **Explanation:** The key to answering this question lies in distinguishing between the **proliferative** effects of estrogen and the **secretory** effects of progesterone on the uterine lining. **1. Why Option A is the Correct Answer:** Estrogen is primarily responsible for the **proliferative phase** of the menstrual cycle. It stimulates the growth and synthetic activity of the endometrial lining (increasing thickness, vascularity, and DNA synthesis). However, the **secretory transformation**—characterized by the coiling of endometrial glands and the secretion of glycogen-rich fluids—is strictly a function of **Progesterone** during the luteal phase. Therefore, estrogen does not stimulate secretory function. **2. Analysis of Incorrect Options:** * **Option B:** Estrogen promotes the **synthetic function** of the endometrium by inducing the synthesis of RNA, proteins, and DNA, leading to cellular hyperplasia and hypertrophy. * **Option C:** Estrogen is the primary hormone responsible for the **development of secondary sexual characteristics** in females, including the widening of the pelvis and female-pattern fat distribution. * **Option D:** At puberty, estrogen stimulates the **growth of mammary ducts** and the deposition of fat in the breasts, leading to breast enlargement (Thelarche). **Clinical Pearls for NEET-PG:** * **Estrogen vs. Progesterone:** Estrogen = Duct growth in breasts; Progesterone = Alveolar/Lobular development. * **Cervical Mucus:** Estrogen makes mucus thin, watery, and alkaline (shows **ferning**), whereas progesterone makes it thick and cellular. * **Bone Health:** Estrogen promotes the closure of epiphyseal plates and inhibits osteoclast activity (preventing osteoporosis).

Q: Which of the following is NOT a feature of inhibin?

Stimulates FSH secretion. **Explanation:** **Inhibin** is a glycoprotein hormone that plays a critical role in the negative feedback regulation of the hypothalamic-pituitary-gonadal axis. **Why Option C is the correct answer (The "NOT" feature):** The primary physiological function of inhibin is to **selectively inhibit** the secretion of **Follicle-Stimulating Hormone (FSH)** from the anterior pituitary. It does not stimulate FSH. This feedback loop is essential for regulating follicular development in females and spermatogenesis in males. **Analysis of other options:** * **Option A:** Inhibin is indeed a **non-steroidal, water-soluble glycoprotein** composed of an alpha and a beta subunit ($\alpha\beta$). * **Option B:** In females, it is primarily secreted by the **granulosa cells** of the developing antral follicles and the **Graafian follicle**. In males, it is secreted by the **Sertoli cells**. * **Option D:** In **Polycystic Ovarian Disease (PCOD/PCOS)**, there is an increased number of small antral follicles. This leads to **elevated levels of Inhibin-B**, which contributes to the characteristic suppression of FSH seen in these patients (leading to a high LH:FSH ratio). **High-Yield Clinical Pearls for NEET-PG:** * **Inhibin A vs. B:** Inhibin **B** is the primary form in the follicular phase (marker of ovarian reserve), while Inhibin **A** peaks in the luteal phase (secreted by the corpus luteum). * **Tumor Marker:** Inhibin is a highly specific tumor marker for **Granulosa Cell Tumors** of the ovary. * **Triple/Quadruple Test:** Inhibin A is measured during the second trimester of pregnancy; **elevated levels** are associated with an increased risk of **Down Syndrome (Trisomy 21)**. * **Activin:** A related protein (beta-beta dimer) that performs the opposite function—it **stimulates** FSH secretion.

Q: Sertoli cells have receptors for which of the following hormones?

Follicle stimulating hormone. **Explanation:** The correct answer is **Follicle Stimulating Hormone (FSH)**. Sertoli cells, often called "nurse cells," are located within the seminiferous tubules and are essential for spermatogenesis. **1. Why FSH is correct:** Sertoli cells are the primary targets for FSH in the male reproductive system. When FSH binds to its G-protein coupled receptors on the Sertoli cell membrane, it stimulates the production of **Androgen Binding Protein (ABP)**, which maintains high local testosterone levels, and **Inhibin**, which provides negative feedback to the anterior pituitary. FSH also promotes the synthesis of nutrients and growth factors required for the maturation of germ cells. **2. Why other options are incorrect:** * **Inhibin:** This is a hormone **produced by** Sertoli cells, not one they have receptors for. It acts on the anterior pituitary to specifically inhibit FSH secretion. * **Luteinizing Hormone (LH):** LH receptors are located on **Leydig cells** (interstitial cells), where LH stimulates the production of testosterone. A common mnemonic is **L**H acts on **L**eydig cells. * **Melatonin:** While melatonin can influence the hypothalamic-pituitary-gonadal axis (typically inhibitory), Sertoli cells are not its primary physiological target in the context of direct hormonal regulation of spermatogenesis. **Clinical Pearls for NEET-PG:** * **Blood-Testis Barrier:** Formed by tight junctions between adjacent Sertoli cells; it protects developing sperm from the immune system. * **Müllerian Inhibiting Substance (MIS):** Also secreted by Sertoli cells in the fetus to cause regression of Müllerian ducts. * **Spermiation:** The process of releasing mature spermatozoa from Sertoli cells into the lumen of seminiferous tubules. * **Hormonal Control:** Spermatogenesis requires both **FSH** (acting on Sertoli cells) and **Testosterone** (produced by Leydig cells under LH influence).

Q: What is the action of oxytocin, except?

Contraction of the lower uterine segment. ### Explanation Oxytocin is a peptide hormone synthesized in the **paraventricular nucleus** of the hypothalamus and secreted by the posterior pituitary. Its primary role is to stimulate smooth muscle contraction in specific reproductive tissues. **Why Option D is the Correct Answer:** During labor, oxytocin promotes **fundal dominance**. It causes strong, rhythmic contractions of the **upper segment** of the uterus (the fundus and body) while simultaneously causing the **lower uterine segment to relax and thin out**. This physiological gradient is essential to push the fetus downward and allow the cervix to dilate. If the lower segment contracted along with the upper segment, the fetus would be trapped, and the cervix would not dilate. **Analysis of Incorrect Options:** * **Option A (Increased contractility):** Oxytocin increases the force and frequency of uterine contractions by increasing intracellular calcium and stimulating prostaglandin synthesis. * **Option B & C (Myoepithelial cells/Milk ejection):** Oxytocin causes the contraction of **myoepithelial cells** surrounding the mammary alveoli. This forces milk into the larger ducts and out through the nipple, a process known as the **Milk Ejection Reflex** (or "let-down" reflex). **High-Yield Clinical Pearls for NEET-PG:** * **Ferguson Reflex:** A neuroendocrine reflex where vaginal/cervical stretching triggers oxytocin release, creating a positive feedback loop during labor. * **Receptor Regulation:** Estrogen **upregulates** oxytocin receptors (increasing sensitivity at term), while progesterone **downregulates** them. * **Clinical Use:** Synthetic oxytocin (Pitocin) is the drug of choice for **Induction of Labor** and the prevention/treatment of **Postpartum Hemorrhage (PPH)**. * **Side Effect:** At high doses, oxytocin has an **ADH-like effect**, which can lead to water intoxication and hyponatremia.

Q: If the corpus luteum is functioning, its endocrine function is initiated by the influence of which of the following hormones?

LH. **Explanation:** The **Corpus Luteum (CL)** is a temporary endocrine structure formed from the remnants of the Graafian follicle after ovulation. Its primary function is the secretion of progesterone and estrogen to maintain the endometrial lining for potential implantation. **Why LH is the Correct Answer:** The initiation and maintenance of the corpus luteum are strictly dependent on **Luteinizing Hormone (LH)**. Following the LH surge, which triggers ovulation, the remaining granulosa and theca cells undergo "luteinization." LH stimulates these cells to increase their expression of steroidogenic enzymes, effectively turning the follicle into a progesterone-producing factory. Without the continuous trophic support of LH (or hCG in pregnancy), the corpus luteum would undergo luteolysis (degeneration). **Why Other Options are Incorrect:** * **FSH (Follicle Stimulating Hormone):** While FSH is crucial for the recruitment and growth of follicles during the follicular phase, it does not initiate the endocrine function of the corpus luteum. * **GnRH (Gonadotropin-Releasing Hormone):** GnRH is the upstream hypothalamic hormone that stimulates the release of LH and FSH from the anterior pituitary. It does not act directly on the ovary to initiate luteal function. **High-Yield Clinical Pearls for NEET-PG:** * **Luteal Phase Length:** The lifespan of the corpus luteum is remarkably constant at approximately **14 days** in a non-pregnant cycle. * **Rescue of Corpus Luteum:** If fertilization occurs, **hCG** (Human Chorionic Gonadotropin), which is an analog of LH, binds to LH receptors to "rescue" the corpus luteum, maintaining progesterone production until the placenta takes over (the **luteal-placental shift** at 7–9 weeks). * **Hormone Secretion:** The corpus luteum secretes **Progesterone** (predominant), Estrogen, and **Inhibin A**.

Question 1

Which statement is true about spermatogenesis?

Accepted Answer

It takes 74 days to complete.

Answer

It takes place in the spermatic cord.

Answer

Meiosis occurs only after the formation of the secondary spermatocyte.

Answer

Spermatids are formed from spermatozoa.

Question 2

Semen examination of a man showed counts of 25 million/cu.mm, volume - 1.5 ml; motility - 15%; Morphology - 15%. What is the diagnosis?

Accepted Answer

Asthenospermia

Answer

Azoospermia

Answer

Oligospermia

Answer

Teratospermia

Question 3

Serum inhibin B is secreted by ovarian granulosa cells starting at which stage?

Accepted Answer

Preantral follicle stage

Answer

Primordial follicle stage

Answer

Early antral stage

Answer

Preovulatory stage

Question 4

Which of the following is NOT a function of estrogen?

Accepted Answer

Stimulation of secretory function on the endometrium

Answer

Stimulation of synthetic function on the endometrium

Answer

Development of secondary sexual characters in females

Answer

Breast enlargement during puberty

Question 5

Which of the following statements is correct regarding milk secretion?

Accepted Answer

The neuroendocrine pathway involving the posterior pituitary is implicated.

Answer

Secretion occurs due to the contraction of lactiferous sinuses stimulated by oxytocin.

Answer

Vasopressin hormone plays a role in milk secretion.

Answer

Milk secretion is affected by emotional state.

Question 6

Which of the following is NOT a feature of inhibin?

Accepted Answer

Stimulates FSH secretion

Answer

Non-steroidal water-soluble protein

Answer

Secreted by Graafian follicle

Answer

Increased secretion of inhibin occurs in polycystic ovarian disease

Question 7

Arrange the steps of spermatogenesis in the sequence of their formation.

Accepted Answer

Spermatogonium > Spermatocyte > Spermatid > Spermatozoa

Answer

Spermatocyte > Spermatogonium > Spermatid > Spermatozoa

Answer

Spermatogonium > Spermatocyte > Spermatozoa > Spermatid

Answer

Spermatozoa > Spermatogonium > Spermatocyte > Spermatid

Question 8

Sertoli cells have receptors for which of the following hormones?

Accepted Answer

Follicle stimulating hormone

Answer

Inhibin

Answer

Luteinizing hormone

Answer

Melatonin

Question 9

What is the action of oxytocin, except?

Accepted Answer

Contraction of the lower uterine segment

Answer

Increased contractility of the uterus

Answer

Contraction of myoepithelial cells

Answer

Milk ejection

Question 10

If the corpus luteum is functioning, its endocrine function is initiated by the influence of which of the following hormones?

Accepted Answer

LH

Answer

FSH

Answer

GnRH

Answer

All of the above

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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