A rise in increasing hormone and follicle-stimulating hormone triggers ovulation at what stage in the ovarian cycle?
14 days
5 days
28 days
21 days
The correct answer and explanation is:
The correct answer is 14 days.
In the ovarian cycle, ovulation typically occurs around day 14, although it can vary slightly depending on the individual. The cycle is divided into three main phases: the follicular phase, ovulation, and the luteal phase.
- Follicular Phase (Day 1–14): This phase begins on the first day of menstruation and lasts until ovulation. During this time, the hypothalamus in the brain releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones promote the growth of ovarian follicles. The most dominant follicle will eventually mature and prepare for ovulation.
- Ovulation (Around Day 14): A surge in LH and FSH triggers ovulation, which is the release of a mature egg (oocyte) from the dominant follicle. This surge occurs approximately 24–36 hours before ovulation and is essential for the release of the egg from the follicle. The LH surge causes the follicle to rupture, releasing the egg into the fallopian tube where fertilization may occur.
- Luteal Phase (Day 15–28): After ovulation, the ruptured follicle transforms into a structure called the corpus luteum, which secretes progesterone. Progesterone helps prepare the uterine lining for a potential pregnancy. If fertilization does not occur, the corpus luteum degenerates, leading to a drop in progesterone and the onset of menstruation.
Ovulation usually happens around day 14 in a 28-day cycle, but the length of the cycle can affect the timing. The key point is that the increase in LH and FSH levels is a critical trigger for ovulation, occurring near the midpoint of the cycle.