Hi everyone,
Welcome to our video.
Today,
We will be discussing the notorious period.
Almost all women must deal with the trials and tribulations
of menstruation at some point in their lives. The cramping, aching,
and seemingly never-ending bleeding have been familiar,
but dreaded sensations to women all over the world, since
the beginning of humanity.
Althoug we may understand how our body is feeling
during that time of the month,
there is a lot more going on behind the scenes.
So how does menstruation work?
We asked Hannah and Rebecca of Bleed
Free Master, a club on McMaster campus dedicated to tackling
menstrual stigmas and barriers to help us deconstruct the period.
Well to start off, after hitting puberty,
every woman enters the constant cycle that continues until menopause.
This cycle is called a menstrual cycle,
and on average runs for 28 days.
Menstrual cycle works in the series of hormones that are
released in the body at three
key centers:
the hypothalamus of the brain, the anterior pituitary and the ovaries.
To begin the cycle,
a hormone called Gonadotropin Releasing Hormone or GnRH
is released from the hypothalamus. This hormone acts on the
anterior,
pituitary by stimulating the gland to release two
new hormones: follicle-stimulating hormone or FSH and luteinizing hormone
or LH.
FSH and LH travel down the bloodstream until they reach
the ovaries, which are their main site of action.
These hormones are extremely important for the growth of eggs,
within the ovaries. FHS stimulate the development of the follicle
within the ovary,
which is a sac
that contains the immature eggs.
This sac is composed of granular cells,
called granulosa,
which produces the steroid hormone estrogen. LH on the other hand triggers
the egg to be released from the follicle sac
causing ovulation to occur.
Ovulation is essentially just
egg being released from the ovary and down the uterine tube.
After ovulation,
the leftovers cells from the follicle become known as the
corpus luteum.
At this point,
LH acts on the corpus luteum to promote the
production of the steroid hormone progesterone within it.
Estrogen
and progesterone are the two key hormones,
which control what happens to the female endometrium?
Or in other words,
the lining of the uterus.
During menstruation.
All together, these hormones regulate each other,
using the mechanism,
call negative feedback. To explain how negative feedback works,
let's imagine that you are hungry.
When you're hungry,
your body tells you it wants to eat.
As you eat the food in your stomach,
starts to tell your body to slow down and the
hunger begins to die down.
Eventually you stop eating because your body is telling you
that you don't need any more food.
Although we aren't conscious of it,
the same sort of thing is happening
in our bodies with our hormones.
GnRH, FSH and LH can be thought of as the
food for the ovaries and estrogen and progesterone are the
signals that tell the body to stop eating when it
has had enough.
Eventually,
once all the estrogen and progesterone has been metabolized
in the liver, the cycle repeats itself,
just the same as the way,
your body tells us that we are hungry again,
once we have digested
all our food.
So, while GnRH, FSH and LH, stimulate the
production of estrogen and progesterone, estrogen and progesterone
inhibits
the release of GnRH,
FSH,
and LH.
Let's talk more about the endometrium which is essentially what
this period
is all about.
The endometrium is the outer layer of the uterus that is shed
during menstruation.
There are three key phases of the menstrual cycle,
which are seen within their endometrium.
The first is the proliferative phase,
the proliferative phase occurs,
after menstruation and before ovulation. We will say that day
4-7 of the menstrual cycle marks the beginning of this phase.
The proliferative phase last until day 14 and is characterized by
the rapid growth of the endometrium.
Typically at the start of the proliferative phase,
the endometrium is only 2 mm thick, but by 5 days in, it is
grown to 10 mm thick.
This crazy amount of cell growth is caused by estrogen,
which is being released by the follicle in the ovary.
Estrogen receptors are expressed within the endometrium and mediate,
the actions of estrogen.
At day 14
there's a surge in the
level of LH, releasing the egg from the follicle
and leaving the corpus luteum in its place.
This marks
the beginning of the second phase of the menstrual cycle, the secretory phase,
which occurs from day 14 to day 28.
in the secretory phase, progesterone is continuously being released
by the corpus luteum. Progesterone stops the
growth of the endometrium,
by significantly lowering
the expression of estrogen receptors within itself.
Progesterone also,
accumulates sugar like glycogen in proteins like collagen which triggers
the endometrial glands to release their contents through secretion and
provoke cells to enlarge. The goal here is to create a perfect
environment for a fertilized egg implants to develop in, which
occurs in the first stages of pregnancy.
The effects of progesterone are induced by the presence of
progesterone receptors
within the endometrium. Around day 28,
in the event that pregnancy has not occurred the body
realizes
but there is no fertilized eggs to be implanted in
the uterus, causing the corpus luteum
to breakdown.
This is due to
a decline in progesterone levels.
With a lack of progesterone in the uterus,
there's nothing to keep the endometrium where it is,
so it begins to shed by, signalling the start of
the menstrual phase where we begin again at day one.
We hope all the women listening have gained a little
bit more of an understanding about what is really going
on during their period,
and maybe even a little bit more of an appreciation
for it.
And to the guys up there,
just count yourself lucky.
Thanks for listening.
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