Ovulation and Fertilization — MCQs
Arrange the cells according to their positions from the basal layer towards the lumen in the seminiferous tubules:- 1. Spermatogonia 2. Primary spermatocyte 3. Spermatid 4. Spermatozoa
Increased LH secretion just before ovulation is due to
The mechanism of action of emergency contraception includes the following except:
By which mechanism do LH and FSH primarily return to baseline levels after ovulation?
What physiological event occurs during ovulation?
Where does meiosis occur in human females?
Ovulation occurs how long after the LH surge peak?
Ovulation is associated with sudden rise in:
All are steps of GIFT, except:
In a lady with a regular 28-day menstrual cycle, what is the 'safe period'?
Ovulation and Fertilization Indian Medical PG Practice Questions and MCQs
Question 1: Arrange the cells according to their positions from the basal layer towards the lumen in the seminiferous tubules:- 1. Spermatogonia 2. Primary spermatocyte 3. Spermatid 4. Spermatozoa
- A. 2,1,3,4
- B. 1,2,3,4 (Correct Answer)
- C. 1,3,2,4
- D. 4,3,2,1
Explanation: ***1,2,3,4*** - This sequence accurately represents the **developmental progression of male germ cells** from the basal lamina towards the lumen of the seminiferous tubule [1], [2]. - **Spermatogonia** are stem cells located near the basal lamina [1], which then differentiate into **primary spermatocytes**, followed by **spermatids**, and finally maturing into **spermatozoa** that are released into the lumen [2]. *2,1,3,4* - This order is incorrect because **primary spermatocytes** develop from spermatogonia [2], meaning spermatogonia should precede primary spermatocytes in the sequence. - The initial cell in the spermatogenic lineage is the **spermatogonium**, found at the base of the tubule [1]. *1,3,2,4* - This sequence is incorrect as **primary spermatocytes** undergo meiosis to form secondary spermatocytes, which then become spermatids [2]. - Therefore, **spermatids** develop *after* primary spermatocytes, not before them. *4,3,2,1* - This order is a reversal of the actual developmental process and spatial arrangement within the seminiferous tubule. - **Spermatozoa** are the most mature cells and are found closest to the lumen [1], while **spermatogonia** are located at the basal layer [1].
Question 2: Increased LH secretion just before ovulation is due to
- A. Positive feed-back by FSH
- B. Positive feed-back by progesterone
- C. Positive feed-back by relaxin
- D. Positive feed-back by estrogen (Correct Answer)
Explanation: ***Positive feed-back by estrogen*** - The surge in **estrogen** from the dominant follicle during the late follicular phase stimulates the hypothalamus and anterior pituitary. - This high level of estrogen switches from negative to **positive feedback**, leading to a dramatic increase in **GnRH** and subsequently **LH** secretion. *Positive feed-back by FSH* - While **FSH** plays a role in follicular development, its primary function is to stimulate estrogen production, not directly trigger the LH surge via positive feedback. - FSH levels actually decline during the late follicular phase as estrogen levels rise, before a small secondary surge alongside LH. *Positive feed-back by progesterone* - **Progesterone** levels are low before ovulation and begin to rise significantly only after the **LH surge** and ovulation, secreted primarily by the corpus luteum. - While progesterone can contribute to a further LH surge in some contexts, it is not the primary initiator of the pre-ovulatory LH surge. *Positive feed-back by relaxin* - **Relaxin** is primarily involved in relaxing pelvic ligaments and softening the cervix, especially during pregnancy. - It does not play a role in the **positive feedback mechanism** that triggers the pre-ovulatory LH surge.
Question 3: The mechanism of action of emergency contraception includes the following except:
- A. Degeneration of corpus luteum (Correct Answer)
- B. Prevention of implantation of fertilized egg.
- C. Inhibition of fertilization
- D. By preventing or delaying ovulation
Explanation: ***Degeneration of corpus luteum*** - Emergency contraception primarily works by interfering with ovulation and fertilization. It does **not directly cause degeneration of the corpus luteum**. - The **corpus luteum** forms after ovulation, and its degradation is a natural process (luteolysis) if pregnancy does not occur. Emergency contraception acts earlier in the reproductive process and does not target the corpus luteum. - This is the **correct answer** as it is NOT a mechanism of emergency contraception. *By preventing or delaying ovulation* - This is the **primary mechanism** of action for most forms of emergency contraception, particularly those containing **levonorgestrel (LNG)** and **ulipristal acetate (UPA)**. - By delaying the release of an egg from the ovary, it prevents the possibility of fertilization. - This is the most established and clinically significant mechanism. *Inhibition of fertilization* - Emergency contraception may affect fertilization by altering **cervical mucus** thickness, making it less penetrable to sperm. - Some evidence suggests effects on **sperm motility** or function, though this mechanism is less well-established than ovulation inhibition. - This represents a possible secondary mechanism. *Prevention of implantation of fertilized egg* - **Current evidence does NOT support this as a mechanism** for levonorgestrel or ulipristal acetate emergency contraception. - Studies by **WHO, ACOG, FIGO, and ICMR** have shown that LNG-EC is ineffective once fertilization has occurred. - The **copper IUD** used for emergency contraception may have some anti-implantation effects due to its inflammatory action on the endometrium. - However, for hormonal EC (the most common form), prevention of implantation is **not an established mechanism** based on current medical evidence.
Question 4: By which mechanism do LH and FSH primarily return to baseline levels after ovulation?
- A. Negative feedback on GnRH from testosterone
- B. LH surge
- C. Negative feedback on GnRH by estradiol
- D. Negative feedback on gonadotropin-releasing hormone (GnRH) by progesterone (Correct Answer)
Explanation: ***Negative feedback on GnRH by progesterone*** - After ovulation, the **corpus luteum** secretes **progesterone** (and estradiol), which exerts powerful **negative feedback** on the hypothalamus and pituitary - **Progesterone** is the **dominant hormone** in the **luteal phase** that suppresses **GnRH** pulsatility, leading to decreased secretion of both **LH** and **FSH** to baseline levels - This negative feedback maintains low gonadotropin levels throughout the luteal phase until corpus luteum regression *Negative feedback on GnRH by estradiol* - **Estradiol** does provide negative feedback, particularly in the **early-mid follicular phase**, where it primarily suppresses **FSH** secretion - In the luteal phase, estradiol works **synergistically with progesterone**, but **progesterone is the dominant feedback signal** for returning both LH and FSH to baseline after ovulation - Estradiol alone (without progesterone) triggers the **LH surge** via positive feedback at high concentrations *Negative feedback on GnRH from testosterone* - This mechanism is specific to **males**, where **testosterone** from Leydig cells provides negative feedback to regulate **GnRH**, **LH**, and **FSH** secretion - In females, testosterone plays only a minor role in feedback regulation of the hypothalamic-pituitary-gonadal axis *LH surge* - The **LH surge** is a **positive feedback** phenomenon triggered by high **estradiol** levels in the late follicular phase - This represents the **peak** of LH secretion that triggers ovulation, not a mechanism for returning LH and FSH to **baseline** levels - After the surge, LH falls due to negative feedback from progesterone and estradiol during the luteal phase
Question 5: 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.
Question 6: 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 7: Ovulation occurs how long after the LH surge peak?
- A. 48-72 hours
- B. 72-96 hours
- C. 24-48 hours
- D. 12-24 hours (Correct Answer)
Explanation: ***12-24 hours*** - Ovulation, the release of a mature egg from the **ovary**, typically occurs within **12 to 24 hours after the peak of the luteinizing hormone (LH) surge**. - The LH surge itself usually lasts 24 to 48 hours and is a critical signal for the final maturation and release of the oocyte. *24-48 hours* - While the **LH surge** can last up to 48 hours, **ovulation** (the actual release of the egg) generally happens more rapidly, usually within 12-24 hours of the *peak* of this surge. - This timeframe is a common misconception, as it refers more to the duration of the surge rather than the precise timing of ovulation post-peak. *48-72 hours* - Ovulation rarely occurs this late after the peak of the **LH surge**; if it does, it suggests a potential delay or irregularity in the **ovulatory process**. - The window for successful fertilization is relatively narrow and aligns with the more immediate post-surge timing. *72-96 hours* - This time frame is significantly beyond the typical window for **ovulation** following the **LH surge**. - By this point, the egg would have either been released or the ovulatory event would have passed without the egg releasing.
Question 8: Ovulation is associated with sudden rise in:
- A. Oxytocin
- B. LH (Correct Answer)
- C. Testosterone
- D. Prolactin
Explanation: ***LH*** - A **surge in Luteinizing Hormone (LH)** is the primary trigger for ovulation, initiating the final maturation and release of the ovum from the ovarian follicle. - This LH surge typically occurs about **24-36 hours before ovulation** and is a critical event in the menstrual cycle. *Oxytocin* - **Oxytocin** is primarily associated with uterine contractions during childbirth and milk ejection during lactation. - While it has roles in reproduction, it does not directly cause or surge at the time of ovulation in the way LH does. *Testosterone* - **Testosterone** is predominantly an androgen, playing a role in male sexual development and secondary sex characteristics, though it is present in lower levels in females. - It is not directly linked to the acute hormonal surge that triggers ovulation. *Prolactin* - **Prolactin** is primarily responsible for milk production (lactation) after childbirth. - High levels of prolactin can actually inhibit ovulation by suppressing gonadotropin-releasing hormone (GnRH), rather than promoting it.
Question 9: All are steps of GIFT, except:
- A. Transfer of unfertilized egg into the fallopian tube
- B. Fertilization of oocyte in lab (Correct Answer)
- C. Ovulation stimulation
- D. Oocyte retrieval
Explanation: ***Fertilization of oocyte in lab*** - **Gamete intrafallopian transfer (GIFT)** involves the transfer of both sperm and eggs directly into the fallopian tube, where **fertilization occurs naturally** within the body. - The step of **fertilization in the lab** (in vitro fertilization) is characteristic of **IVF**, not GIFT. *Transfer of unfertilized egg into the fallopian tube* - In GIFT, **harvested eggs** (oocytes) are mixed with sperm and then immediately **transferred into the fallopian tube**. - This allows natural fertilization to occur within the woman's body, which is a key distinction of GIFT from IVF. *Ovulation stimulation* - Before GIFT, women undergo **controlled ovarian hyperstimulation** to produce multiple mature follicles and increase the chances of successful egg retrieval. - This process is essential for obtaining a sufficient number of **oocytes** for transfer. *Oocyte retrieval* - Once the follicles are mature, **oocytes are retrieved** from the ovaries, typically through transvaginal ultrasound-guided aspiration. - These retrieved oocytes are then prepared for transfer along with sperm into the fallopian tubes.
Question 10: In a lady with a regular 28-day menstrual cycle, what is the 'safe period'?
- A. Initial 14 days
- B. Later 14 days
- C. First and last seven days (Correct Answer)
- D. First seven days only
Explanation: ***First and last seven days*** - In a typical 28-day cycle, **ovulation** usually occurs around day 14. Sperm can survive for up to 5 days, and the egg is viable for about 24 hours. Therefore, avoiding unprotected intercourse from approximately day 7 to day 19 would be considered within the fertile window. The "safe period" refers to days with a lower probability of conception. - The **first seven days** (including menstruation) and the **last seven days** (preceding the next menstrual period) are generally considered the least fertile times, as they are furthest from ovulation. *Initial 14 days* - This period includes the follicular phase, leading up to and including **ovulation**. - The **fertile window** typically encompasses several days before ovulation, the day of ovulation, and the day after, making the initial 14 days a high-risk period, not a safe one. *Later 14 days* - This period includes the **luteal phase** after ovulation has occurred. - While the latter part of this period (days 21-28) is generally less fertile, the days immediately following ovulation (around days 15-18) still carry a risk of conception if the egg is viable or if ovulation was delayed. *First seven days only* - While the first seven days are generally considered a **low-risk period**, relying solely on this neglects the increased risk shortly before and during ovulation. - This option only covers a portion of the "safe period" and does not account for the reduced fertility towards the end of the menstrual cycle.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free