Approximately how many oocytes will mature and be ovulated during a woman’s reproductive lifespan?
50–100
100–200
400–500
1,000–2,000
The Correct Answer is C
Ovarian follicular reserve refers to the finite number of oocytes a female is born with. At birth, ovaries contain about 1–2 million primary oocytes, decreasing to about 300,000–400,000 by puberty due to atresia. Only about 400–500 of these will fully mature and be ovulated during the reproductive lifespan, while the remainder degenerate. Normal reproductive lifespan averages 35–40 years from menarche to menopause.
Rationale for correct answer
C. Over an average reproductive lifespan, with approximately 1 ovulation per menstrual cycle and about 12 cycles per year, only around 400–500 oocytes are released; the rest undergo atresia.
Rationale for incorrect answers
A. 50–100 is too low, as this would account for fewer than 10 years of ovulatory cycles, which is far shorter than the normal reproductive span.
B. 100–200 is still below the expected number, corresponding to fewer than 20 years of ovulations.
D. 1,000–2,000 is too high, as this would require more than double the number of ovulatory cycles that normally occur in a woman’s reproductive life.
Take home points
- Females are born with a finite, non-renewable oocyte reserve.
- Only 400–500 oocytes are ovulated in a lifetime.
- The majority of oocytes undergo atresia before ovulation.
- Menstrual cycles average 12 per year over 35–40 reproductive years.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is ["A","B","D"]
Explanation
Progesterone is a steroid hormone mainly produced by the corpus luteum and later by the placenta during pregnancy. It regulates the endometrium, prepares the uterus for implantation, and maintains pregnancy by inhibiting uterine contractions. It increases basal body temperature by about 0.3–0.5 °C post-ovulation. Normal serum progesterone is <1 ng/mL in the follicular phase and >3 ng/mL in the luteal phase.
Rationale for correct answers
A. Progesterone increases basal body temperature by acting on the hypothalamic thermoregulatory center, raising temperature by 0.3–0.5 °C after ovulation. This physiologic rise helps in ovulation detection.
B. Progesterone maintains the uterine lining by supporting secretory phase changes in the endometrium, preventing shedding during pregnancy. It suppresses myometrial contractility to allow embryo implantation and growth.
D. Progesterone softens pelvic ligaments, particularly during late pregnancy, by influencing connective tissue remodeling, aiding in birth canal flexibility.
Rationale for incorrect answers
C. Progesterone does not stimulate ovulation; instead, luteinizing hormone (LH) surge from the anterior pituitary triggers ovulation. Progesterone levels rise only after ovulation in the luteal phase.
E. Progesterone does not promote endometrial growth; estrogen is the main hormone driving proliferative phase endometrial growth. Progesterone acts after proliferation to convert the endometrium into a secretory form for implantation.
Take home points
• Progesterone prepares and maintains the endometrium for implantation.
• Estrogen drives endometrial proliferation, progesterone drives secretory changes.
• Progesterone inhibits uterine contractility to prevent miscarriage.
• LH, not progesterone, triggers ovulation.
Correct Answer is B
Explanation
Oogenesis is the process of haploid gamete formation in females, beginning before birth and completed only if fertilization occurs. Primary oocytes are arrested in prophase I from fetal life until ovulation. At ovulation, meiosis I completes, producing the secondary oocyte, which arrests in metaphase II until sperm penetration triggers completion of meiosis II. Normal female gametes have 23 chromosomes (n).
Rationale for correct answer
B. The secondary oocyte is arrested in metaphase II due to cytostatic factor, maintaining meiotic arrest until fertilization. Sperm entry activates calcium-dependent pathways that resume meiosis II, producing the ovum and second polar body.
Rationale for incorrect answers
A. Prophase I arrest occurs in primary oocytes from fetal life until puberty; this is before formation of the secondary oocyte.
C. Anaphase II is the stage where sister chromatids separate during completion of meiosis II; it occurs only after fertilization starts, not before.
D. Telophase I follows anaphase I when primary oocytes complete meiosis I; this produces the secondary oocyte but is not the arrest point before fertilization.
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