Which of the following is correct about the life span of an ovum?

Appeared in: NORCERT 8 Mains-2025

Explanation

After ovulation, the ovum (secondary oocyte) is released from the ovary and enters the fallopian tube.
The ovum remains viable and capable of being fertilized for a relatively short window of only 12 to 24 hours.
For pregnancy to occur, fertilization must happen within this timeframe in the ampulla of the fallopian tube.
If fertilization does not occur, the ovum degenerates and is phagocytized (reabsorbed by the body).

Option B: This time frame (48-72 hours) represents the viability of sperm within the female reproductive tract, not the ovum.
Option C: This range is slightly longer than the accepted viability period for an ovum. While fertilization might be possible at the 24-hour mark, the ovum's quality rapidly declines, making fertilization beyond 24 hours highly unlikely.
Option D: This is a duplicate of option B and is incorrect for the same reason. The 48-72 hour window is the lifespan of sperm, not the ovum.

Visual 1: Diagram - A timeline illustrating the female menstrual cycle. It should highlight the moment of ovulation and the subsequent 12-24 hour 'fertilization window' for the ovum in the fallopian tube, contrasted with the 3-5 day 'fertile window' created by sperm viability.
Visual 2: Infographic - A comparison table showing the key differences between the ovum and sperm, including their size, motility, and lifespan after release/ejaculation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Viability of the human ovum post-ovulation as background academic context rather than a clinical decision trigger.
Understanding the distinct lifespans of the ovum and sperm is fundamental for patient education regarding conception and contraception.
Nurses use this knowledge to counsel couples on the timing of intercourse to maximize the chances of pregnancy, explaining that the 'fertile window' starts days before ovulation due to sperm longevity.
This concept is also crucial for natural family planning methods, where couples track ovulation to either achieve or avoid pregnancy.

How to Approach the Question

Identify the core concept being tested: The question asks for the lifespan (viability) of an ovum.
Recall the key physiological facts about reproduction. Remember that the female egg has a very short lifespan compared to male sperm.
Differentiate between the viability of the ovum (egg) and the spermatozoon (sperm). The ovum is viable for about 12-24 hours. Sperm can survive for several days (48-72 hours or more).
Evaluate the given options against your recalled knowledge.
Option A (12-24 hours) directly matches the known lifespan of an ovum.
Options B and D (48-72 hours) match the lifespan of sperm, making them incorrect distractors.

Concept Tested & Keywords

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Practise the full NORCERT 8 Mains-2025

Attempt every question from this paper in a timed mock, then review the full solution for each one.