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.
