In oogenesis, the resumption of meiotic division and release of first polar body occur during:?

RUHS, Jaipur, PB B.Sc Nursing Entrance-2022

Obstetrics & Gynaecology

Easy

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2022

Explanation

The question asks to identify the event during which the first meiotic division resumes and the first polar body is released.
In oogenesis, primary oocytes are arrested in Prophase I from fetal life.
The mid-cycle surge of Luteinizing Hormone (LH), which occurs approximately 24-36 hours before ovulation, provides the signal for the primary oocyte to resume and complete Meiosis I.
This division results in an unequal distribution of cytoplasm, forming a large secondary oocyte and a small, non-functional first polar body.
Therefore, this event is directly linked to the hormonal changes that trigger ovulation.

Option A: Menstruation is the shedding of the endometrial lining of the uterus. It marks the beginning of a new menstrual cycle and occurs when fertilization has not happened. It is not a trigger for meiotic division.
Option C: Fertilization is the trigger for the completion of the second meiotic division. When a sperm penetrates the secondary oocyte (which is arrested in Metaphase II), it signals the oocyte to complete Meiosis II, resulting in a mature ovum and the release of the second polar body.
Option D: Implantation is the process where the blastocyst (the early embryo) attaches to the wall of the uterus. This occurs approximately 6-12 days after fertilization, long after both meiotic divisions are complete.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Oogenesis and Meiotic Division Timing as background academic context rather than a clinical decision trigger.
Understanding the timing of oocyte maturation is fundamental for reproductive medicine, especially in the context of infertility treatments.
In Assisted Reproductive Technologies (ART) like In Vitro Fertilization (IVF), hormonal treatments are used to mimic the natural LH surge to mature multiple oocytes for retrieval just before they would be ovulated.
Knowledge of meiotic arrest is crucial for genetic counseling, as errors in meiotic division (nondisjunction) can lead to aneuploidies (abnormal number of chromosomes), such as Trisomy 21 (Down syndrome), with the risk increasing with maternal age.

How to Approach the Question

First, identify the key process in the question stem: 'resumption of meiotic division and release of first polar body'. This specifically refers to the completion of Meiosis I.
Recall the stages of oogenesis. Remember that oocytes are arrested twice during meiosis.
Connect the hormonal events of the menstrual cycle to the meiotic events. The LH surge is the key trigger for the final maturation of the oocyte before ovulation.
Evaluate each option based on this knowledge:
Menstruation is the end of the cycle if no pregnancy occurs.
Ovulation is the release of the egg, preceded by the LH surge which completes Meiosis I.

Concept Tested & Keywords

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