On day 14 of a 28-day menstrual cycle, there is a sharp LH surge lasting 36–48 hours. Which cellular event in the dominant follicle does the LH surge directly trigger?
- A Resumption of meiosis I in the primary oocyte, cumulus expansion, and luteinization of granulosa cells, culminating in ovulation ~36 hours later ✓
- B Immediate exocytosis of the mature secondary oocyte into the peritoneal cavity within 2 hours
- C FSH receptor upregulation in granulosa cells causing estradiol production surge before ovulation
- D Progesterone decline from the dominant follicle signaling the hypothalamus to release GnRH for the surge
Correct answer: A. Resumption of meiosis I in the primary oocyte, cumulus expansion, and luteinization of granulosa cells, culminating in ovulation ~36 hours later
Explanation
The LH surge acts on LH receptors in the dominant follicle to resume meiosis I (which was arrested in prophase I since fetal life), triggering maturation division to produce the secondary oocyte (arrested at metaphase II). Simultaneously, LH promotes prostaglandin synthesis, matrix metalloprotease activation for follicle wall rupture, and initiation of luteinization of granulosa/theca cells. Ovulation typically occurs 36–44 hours after LH surge onset.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.