Question Video: Recalling the Key Event That Occurs on Day 14 of the Menstrual Cycle Biology

Assume that on day 1 of a menstrual cycle, the uterine lining begins to break down. What will happen around day 14?


Video Transcript

Assume that on day one of a menstrual cycle, the uterine lining begins to break down. What will happen around day 14? (A) Menstruation. (B) Corpus luteum breaks down. (C) An egg will be fertilized. Or (D) ovulation.

To answer this question, let’s take a look at the menstrual cycle and the various processes it involves.

The menstrual cycle is an approximately 28-day process that typically occurs on a cyclical basis from puberty until menopause in many biological females. The menstrual cycle begins on day one until around day six with menstruation, which is sometimes called a period, though the duration will vary considerably between females. Menstruation is when the uterine lining starts to break down and is released along with blood, mucus, and an unfertilized egg cell out of the female’s body through the vagina.

As the question tells us that the breakdown of the uterine lining, and therefore menstruation, occurs on day one of the menstrual cycle and we are looking for the process that occurs around day 14, option (A) is incorrect.

Around halfway through the menstrual cycle, around day 14, the levels of a hormone called estrogen peak. Estrogen stimulates both the thickening of the uterine lining and the production of a different hormone called luteinizing hormone, or LH. A spike in the level of LH in the blood causes an egg cell to be released from a structure called the Graafian follicle in one of the ovaries into its corresponding fallopian tube. This is called ovulation, suggesting that the correct answer to this question is (D).

Let’s check this is correct by completing our exploration of the menstrual cycle.

After the egg cell is released into the fallopian tube, it might or might not be fertilized by a sperm cell there. Successful fertilization depends on a vast range of factors, including both the presence of a biological male’s sperm cells in a female’s fallopian tube and a sperm cell successfully penetrating the egg cell. This is a fairly rare occasion and certainly not a regular part of the monthly menstrual cycle, so we can eliminate option (C).

After the egg cell is released from the ovary, the Graafian follicle that once contained it transforms into a structure called the corpus luteum. The corpus luteum is responsible for releasing a hormone called progesterone that maintains a thick lining of the uterus to prepare it for the potential implantation of an embryo should the egg cell be successfully fertilized by a sperm cell. If the egg cell is not fertilized by a sperm cell, the female body prepares for another menstrual cycle. This involves the corpus luteum in the ovary starting to degrade, which occurs approximately during days 24 to 28. So option (B) is also incorrect.

This means that we can confirm what will happen around day 14 of the typical menstrual cycle and therefore the correct answer to this question. The answer is (D), ovulation.

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