Video Transcript
The diagram provided shows the
changes in the lining of the uterus wall over a typical 28-day cycle. What is the role of progesterone in
relation to the uterus lining? (A) A peak in progesterone
initiates the breakdown of the uterus lining on day one of the menstrual cycle. (B) A decrease in progesterone
stimulates the buildup of the lining after day five of the menstrual cycle. (C) A relatively high level of
progesterone helps maintain the uterus lining between day 14 and day 28,
approximately, of the menstrual cycle. Or (D) progesterone is responsible
for initiating ovulation, so it does not affect the uterus lining.
This question asks about a specific
hormone, progesterone, and its effect on the menstrual cycle in biological
females. We are provided with a graph that
displays the changes in the lining of the uterus over the course of a typical 28-day
menstrual cycle. Let’s take a look at these changes
and some of the hormones that influence them in order to work out the correct answer
to this question.
Between approximately day zero and
six of the menstrual cycle, menstruation, which is sometimes called a period,
occurs. And the thickness of the uterine
lining decreases. During menstruation, the uterine
lining is broken down and shed through the vagina along with blood, an unfertilized
egg cell, and other materials. After menstruation, a hormone
called estrogen is released from the ovaries, which stimulates the uterine lining to
begin to thicken again.
Around day 14, estrogen levels peak
and ovulation occurs. This is when a mature egg cell is
released from an ovary, into the corresponding fallopian tube where it might be
fertilized by a sperm cell. Until this point, progesterone
levels remained fairly low but have been slowly increasing as this hormone is
gradually released from the ovaries.
After ovulation, estrogen levels
drop, while progesterone levels increase further. The increase in progesterone acts
to maintain the thickness of the uterine lining to prepare for the potential
implantation of the embryo that might result from the fertilization of an egg
cell. The levels of progesterone remain
high until the menstrual cycle approaches its end just before day 28. At this point, if the egg cell is
not fertilized by a sperm cell, the levels of progesterone and estrogen drop. So the thickness of the uterine
lining is no longer maintained, and it is shed once more through menstruation. Then, the menstrual cycle can begin
again.
Now we have enough information
about some of the different hormones involved in the regulation of the menstrual
cycle to answer our question correctly. First, we can eliminate answer
option (D), as we know that progesterone does affect the uterus lining, and this
option suggests otherwise. We can also eliminate answer option
(B), as the hormone responsible for stimulating the buildup of the uterus lining is
estrogen, not progesterone. Progesterone decreasing, not
peaking, is partly what stimulates the breakdown of the uterus lining on day one of
the menstrual cycle. So answer option (A) is also
incorrect.
Instead, high levels of
progesterone are responsible for maintaining the thickness of the uterine lining,
which occurs approximately between day 14 when ovulation occurs and day 28 of the
menstrual cycle. This means that the correct answer
to this question is (C). A relatively high level of
progesterone helps maintain the uterus lining between day 14 and 28, approximately,
of the menstrual cycle.
